Add go 1.9 to travis file

- No performance section in README.md, change link to performance to benchmarks

.travis.yml

@@ -2,9 +2,10 @@ language: go
 go:
 - 1.7
 - 1.8
+- 1.9
 - tip
 matrix:
   allow_failures:
       - go: tip
 script:
-    go test -v -race -cpu=1,2,4 ./...
+  go test -v -race -cpu=1,2,4 -bench . -benchmem ./...

README.md

@@ -4,20 +4,25 @@
 
 The zerolog package provides a fast and simple logger dedicated to JSON output.
 
-Zerolog's API is designed to provide both a great developer experience and stunning [performance](#performance). Its unique chaining API allows zerolog to write JSON log events by avoiding allocations and reflection.
+Zerolog's API is designed to provide both a great developer experience and stunning [performance](#benchmarks). Its unique chaining API allows zerolog to write JSON log events by avoiding allocations and reflection.
 
 The uber's [zap](https://godoc.org/go.uber.org/zap) library pioneered this approach. Zerolog is taking this concept to the next level with simpler to use API and even better performance.
 
-To keep the code base and the API simple, zerolog focuses on JSON logging only. As [suggested on reddit](https://www.reddit.com/r/golang/comments/6c9k7n/zerolog_is_now_faster_than_zap/), you may use tools like [humanlog](https://github.com/aybabtme/humanlog) to pretty print JSON on the console during development.
+To keep the code base and the API simple, zerolog focuses on JSON logging only. Pretty logging on the console is made possible using the provided (but inefficient) `zerolog.ConsoleWriter`.
 
+![](pretty.png)
 
 ## Features
 
+* Blazing fast
+* Low to zero allocation
 * Level logging
 * Sampling
+* Hooks
 * Contextual fields
 * `context.Context` integration
 * `net/http` helpers
+* Pretty logging for development
 
 ## Usage
 
@@ -27,6 +32,13 @@ import "github.com/rs/zerolog/log"
 
 ### A global logger can be use for simple logging
 
+```go
+log.Print("hello world")
+
+// Output: {"level":"debug","time":1494567715,"message":"hello world"}
+```
+
+
 ```go
 log.Info().Msg("hello world")
 
@@ -96,6 +108,18 @@ if e := log.Debug(); e.Enabled() {
 // Output: {"level":"info","time":1494567715,"message":"routed message"}
 ```
 
+### Pretty logging
+
+```go
+if isConsole {
+    log.Logger = log.Output(zerolog.ConsoleWriter{Out: os.Stderr})
+}
+
+log.Info().Str("foo", "bar").Msg("Hello world")
+
+// Output: 1494567715 |INFO| Hello world foo=bar
+```
+
 ### Sub dictionary
 
 ```go
@@ -138,10 +162,45 @@ log.Logger = log.With().Str("foo", "bar").Logger()
 ### Log Sampling
 
 ```go
-sampled := log.Sample(10)
+sampled := log.Sample(&zerolog.BasicSampler{N: 10})
 sampled.Info().Msg("will be logged every 10 messages")
 
-// Output: {"time":1494567715,"sample":10,"message":"will be logged every 10 messages"}
+// Output: {"time":1494567715,"level":"info","message":"will be logged every 10 messages"}
+```
+
+More advanced sampling:
+
+```go
+// Will let 5 debug messages per period of 1 second.
+// Over 5 debug message, 1 every 100 debug messages are logged.
+// Other levels are not sampled.
+sampled := log.Sample(zerolog.LevelSampler{
+    DebugSampler: &zerolog.BurstSampler{
+        Burst: 5,
+        Period: 1*time.Second,
+        NextSampler: &zerolog.BasicSampler{N: 100},
+    },
+})
+sampled.Debug().Msg("hello world")
+
+// Output: {"time":1494567715,"level":"debug","message":"hello world"}
+```
+
+### Hooks
+
+```go
+type SeverityHook struct{}
+
+func (h SeverityHook) Run(e *zerolog.Event, level zerolog.Level, msg string) {
+    if level != zerolog.NoLevel {
+        e.Str("severity", level.String())
+    }
+}
+
+hooked := log.Hook(SeverityHook{})
+hooked.Warn().Msg("")
+
+// Output: {"level":"warn","severity":"warn"}
 ```
 
 ### Pass a sub-logger by context
@@ -189,6 +248,15 @@ c = c.Append(hlog.NewHandler(log))
 
 // Install some provided extra handler to set some request's context fields.
 // Thanks to those handler, all our logs will come with some pre-populated fields.
+c = c.Append(hlog.AccessHandler(func(r *http.Request, status, size int, duration time.Duration) {
+    hlog.FromRequest(r).Info().
+        Str("method", r.Method).
+        Str("url", r.URL.String()).
+        Int("status", status).
+        Int("size", size).
+        Dur("duration", duration).
+        Msg("")
+}))
 c = c.Append(hlog.RemoteAddrHandler("ip"))
 c = c.Append(hlog.UserAgentHandler("user_agent"))
 c = c.Append(hlog.RefererHandler("referer"))
@@ -224,7 +292,6 @@ Some settings can be changed and will by applied to all loggers:
 * `zerolog.LevelFieldName`: Can be set to customize level field name.
 * `zerolog.MessageFieldName`: Can be set to customize message field name.
 * `zerolog.ErrorFieldName`: Can be set to customize `Err` field name.
-* `zerolog.SampleFieldName`: Can be set to customize the field name added when sampling is enabled.
 * `zerolog.TimeFieldFormat`: Can be set to customize `Time` field value formatting. If set with an empty string, times are formated as UNIX timestamp.
 	// DurationFieldUnit defines the unit for time.Duration type fields added
 	// using the Dur method.
@@ -250,7 +317,7 @@ Some settings can be changed and will by applied to all loggers:
 * `Dict`: Adds a sub-key/value as a field of the event.
 * `Interface`: Uses reflection to marshal the type.
 
-## Performance
+## Benchmarks
 
 All operations are allocation free (those numbers *include* JSON encoding):
 
@@ -262,7 +329,12 @@ BenchmarkContextFields-8   30000000	    44.9 ns/op	   0 B/op       0 allocs/op
 BenchmarkLogFields-8       10000000	   184 ns/op	   0 B/op       0 allocs/op
 ```
 
-Using Uber's zap [comparison benchmark](https://github.com/uber-go/zap#performance):
+There are a few Go logging benchmarks and comparisons that include zerolog.
+
+- [imkira/go-loggers-bench](https://github.com/imkira/go-loggers-bench)
+- [uber-common/zap](https://github.com/uber-go/zap#performance)
+
+Using Uber's zap comparison benchmark:
 
 Log a message and 10 fields:
 

array.go

@@ -0,0 +1,169 @@
+package zerolog
+
+import (
+	"sync"
+	"time"
+
+	"github.com/rs/zerolog/internal/json"
+)
+
+var arrayPool = &sync.Pool{
+	New: func() interface{} {
+		return &Array{
+			buf: make([]byte, 0, 500),
+		}
+	},
+}
+
+type Array struct {
+	buf []byte
+}
+
+// Arr creates an array to be added to an Event or Context.
+func Arr() *Array {
+	a := arrayPool.Get().(*Array)
+	a.buf = a.buf[:0]
+	return a
+}
+
+func (*Array) MarshalZerologArray(*Array) {
+}
+
+func (a *Array) write(dst []byte) []byte {
+	if len(a.buf) == 0 {
+		dst = append(dst, `[]`...)
+	} else {
+		a.buf[0] = '['
+		dst = append(append(dst, a.buf...), ']')
+	}
+	arrayPool.Put(a)
+	return dst
+}
+
+// Object marshals an object that implement the LogObjectMarshaler
+// interface and append it to the array.
+func (a *Array) Object(obj LogObjectMarshaler) *Array {
+	a.buf = append(a.buf, ',')
+	e := Dict()
+	obj.MarshalZerologObject(e)
+	e.buf = append(e.buf, '}')
+	a.buf = append(a.buf, e.buf...)
+	return a
+}
+
+// Str append the val as a string to the array.
+func (a *Array) Str(val string) *Array {
+	a.buf = json.AppendString(append(a.buf, ','), val)
+	return a
+}
+
+// Bytes append the val as a string to the array.
+func (a *Array) Bytes(val []byte) *Array {
+	a.buf = json.AppendBytes(append(a.buf, ','), val)
+	return a
+}
+
+// Err append the err as a string to the array.
+func (a *Array) Err(err error) *Array {
+	a.buf = json.AppendError(append(a.buf, ','), err)
+	return a
+}
+
+// Bool append the val as a bool to the array.
+func (a *Array) Bool(b bool) *Array {
+	a.buf = json.AppendBool(append(a.buf, ','), b)
+	return a
+}
+
+// Int append i as a int to the array.
+func (a *Array) Int(i int) *Array {
+	a.buf = json.AppendInt(append(a.buf, ','), i)
+	return a
+}
+
+// Int8 append i as a int8 to the array.
+func (a *Array) Int8(i int8) *Array {
+	a.buf = json.AppendInt8(append(a.buf, ','), i)
+	return a
+}
+
+// Int16 append i as a int16 to the array.
+func (a *Array) Int16(i int16) *Array {
+	a.buf = json.AppendInt16(append(a.buf, ','), i)
+	return a
+}
+
+// Int32 append i as a int32 to the array.
+func (a *Array) Int32(i int32) *Array {
+	a.buf = json.AppendInt32(append(a.buf, ','), i)
+	return a
+}
+
+// Int64 append i as a int64 to the array.
+func (a *Array) Int64(i int64) *Array {
+	a.buf = json.AppendInt64(append(a.buf, ','), i)
+	return a
+}
+
+// Uint append i as a uint to the array.
+func (a *Array) Uint(i uint) *Array {
+	a.buf = json.AppendUint(append(a.buf, ','), i)
+	return a
+}
+
+// Uint8 append i as a uint8 to the array.
+func (a *Array) Uint8(i uint8) *Array {
+	a.buf = json.AppendUint8(append(a.buf, ','), i)
+	return a
+}
+
+// Uint16 append i as a uint16 to the array.
+func (a *Array) Uint16(i uint16) *Array {
+	a.buf = json.AppendUint16(append(a.buf, ','), i)
+	return a
+}
+
+// Uint32 append i as a uint32 to the array.
+func (a *Array) Uint32(i uint32) *Array {
+	a.buf = json.AppendUint32(append(a.buf, ','), i)
+	return a
+}
+
+// Uint64 append i as a uint64 to the array.
+func (a *Array) Uint64(i uint64) *Array {
+	a.buf = json.AppendUint64(append(a.buf, ','), i)
+	return a
+}
+
+// Float32 append f as a float32 to the array.
+func (a *Array) Float32(f float32) *Array {
+	a.buf = json.AppendFloat32(append(a.buf, ','), f)
+	return a
+}
+
+// Float64 append f as a float64 to the array.
+func (a *Array) Float64(f float64) *Array {
+	a.buf = json.AppendFloat64(append(a.buf, ','), f)
+	return a
+}
+
+// Time append t formated as string using zerolog.TimeFieldFormat.
+func (a *Array) Time(t time.Time) *Array {
+	a.buf = json.AppendTime(append(a.buf, ','), t, TimeFieldFormat)
+	return a
+}
+
+// Dur append d to the array.
+func (a *Array) Dur(d time.Duration) *Array {
+	a.buf = json.AppendDuration(append(a.buf, ','), d, DurationFieldUnit, DurationFieldInteger)
+	return a
+}
+
+// Interface append i marshaled using reflection.
+func (a *Array) Interface(i interface{}) *Array {
+	if obj, ok := i.(LogObjectMarshaler); ok {
+		return a.Object(obj)
+	}
+	a.buf = json.AppendInterface(append(a.buf, ','), i)
+	return a
+}

array_test.go

@@ -0,0 +1,30 @@
+package zerolog
+
+import (
+	"testing"
+	"time"
+)
+
+func TestArray(t *testing.T) {
+	a := Arr().
+		Bool(true).
+		Int(1).
+		Int8(2).
+		Int16(3).
+		Int32(4).
+		Int64(5).
+		Uint(6).
+		Uint8(7).
+		Uint16(8).
+		Uint32(9).
+		Uint64(10).
+		Float32(11).
+		Float64(12).
+		Str("a").
+		Time(time.Time{}).
+		Dur(0)
+	want := `[true,1,2,3,4,5,6,7,8,9,10,11,12,"a","0001-01-01T00:00:00Z",0]`
+	if got := string(a.write([]byte{})); got != want {
+		t.Errorf("Array.write()\ngot:  %s\nwant: %s", got, want)
+	}
+}

benchmark_test.go

@@ -57,6 +57,18 @@ func BenchmarkContextFields(b *testing.B) {
 	})
 }
 
+func BenchmarkContextAppend(b *testing.B) {
+	logger := New(ioutil.Discard).With().
+		Str("foo", "bar").
+		Logger()
+	b.ResetTimer()
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			logger.With().Str("bar", "baz")
+		}
+	})
+}
+
 func BenchmarkLogFields(b *testing.B) {
 	logger := New(ioutil.Discard)
 	b.ResetTimer()
@@ -71,3 +83,135 @@ func BenchmarkLogFields(b *testing.B) {
 		}
 	})
 }
+
+type obj struct {
+	Pub  string
+	Tag  string `json:"tag"`
+	priv int
+}
+
+func (o obj) MarshalZerologObject(e *Event) {
+	e.Str("Pub", o.Pub).
+		Str("Tag", o.Tag).
+		Int("priv", o.priv)
+}
+
+func BenchmarkLogFieldType(b *testing.B) {
+	bools := []bool{true, false, true, false, true, false, true, false, true, false}
+	ints := []int{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}
+	floats := []float64{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}
+	strings := []string{"a", "b", "c", "d", "e", "f", "g", "h", "i", "j"}
+	durations := []time.Duration{0, 1, 2, 3, 4, 5, 6, 7, 8, 9}
+	times := []time.Time{
+		time.Unix(0, 0),
+		time.Unix(1, 0),
+		time.Unix(2, 0),
+		time.Unix(3, 0),
+		time.Unix(4, 0),
+		time.Unix(5, 0),
+		time.Unix(6, 0),
+		time.Unix(7, 0),
+		time.Unix(8, 0),
+		time.Unix(9, 0),
+	}
+	interfaces := []struct {
+		Pub  string
+		Tag  string `json:"tag"`
+		priv int
+	}{
+		{"a", "a", 0},
+		{"a", "a", 0},
+		{"a", "a", 0},
+		{"a", "a", 0},
+		{"a", "a", 0},
+		{"a", "a", 0},
+		{"a", "a", 0},
+		{"a", "a", 0},
+		{"a", "a", 0},
+		{"a", "a", 0},
+	}
+	objects := []obj{
+		obj{"a", "a", 0},
+		obj{"a", "a", 0},
+		obj{"a", "a", 0},
+		obj{"a", "a", 0},
+		obj{"a", "a", 0},
+		obj{"a", "a", 0},
+		obj{"a", "a", 0},
+		obj{"a", "a", 0},
+		obj{"a", "a", 0},
+		obj{"a", "a", 0},
+	}
+	errs := []error{errors.New("a"), errors.New("b"), errors.New("c"), errors.New("d"), errors.New("e")}
+	types := map[string]func(e *Event) *Event{
+		"Bool": func(e *Event) *Event {
+			return e.Bool("k", bools[0])
+		},
+		"Bools": func(e *Event) *Event {
+			return e.Bools("k", bools)
+		},
+		"Int": func(e *Event) *Event {
+			return e.Int("k", ints[0])
+		},
+		"Ints": func(e *Event) *Event {
+			return e.Ints("k", ints)
+		},
+		"Float": func(e *Event) *Event {
+			return e.Float64("k", floats[0])
+		},
+		"Floats": func(e *Event) *Event {
+			return e.Floats64("k", floats)
+		},
+		"Str": func(e *Event) *Event {
+			return e.Str("k", strings[0])
+		},
+		"Strs": func(e *Event) *Event {
+			return e.Strs("k", strings)
+		},
+		"Err": func(e *Event) *Event {
+			return e.Err(errs[0])
+		},
+		"Errs": func(e *Event) *Event {
+			return e.Errs("k", errs)
+		},
+		"Time": func(e *Event) *Event {
+			return e.Time("k", times[0])
+		},
+		"Times": func(e *Event) *Event {
+			return e.Times("k", times)
+		},
+		"Dur": func(e *Event) *Event {
+			return e.Dur("k", durations[0])
+		},
+		"Durs": func(e *Event) *Event {
+			return e.Durs("k", durations)
+		},
+		"Interface": func(e *Event) *Event {
+			return e.Interface("k", interfaces[0])
+		},
+		"Interfaces": func(e *Event) *Event {
+			return e.Interface("k", interfaces)
+		},
+		"Interface(Object)": func(e *Event) *Event {
+			return e.Interface("k", objects[0])
+		},
+		"Interface(Objects)": func(e *Event) *Event {
+			return e.Interface("k", objects)
+		},
+		"Object": func(e *Event) *Event {
+			return e.Object("k", objects[0])
+		},
+	}
+	logger := New(ioutil.Discard)
+	b.ResetTimer()
+	for name := range types {
+		f := types[name]
+		b.Run(name, func(b *testing.B) {
+			b.RunParallel(func(pb *testing.PB) {
+				for pb.Next() {
+					f(logger.Info()).Msg("")
+				}
+			})
+		})
+	}
+}

console.go

@@ -0,0 +1,117 @@
+package zerolog
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"io"
+	"sort"
+	"strconv"
+	"strings"
+	"sync"
+)
+
+const (
+	cReset    = 0
+	cBold     = 1
+	cRed      = 31
+	cGreen    = 32
+	cYellow   = 33
+	cBlue     = 34
+	cMagenta  = 35
+	cCyan     = 36
+	cGray     = 37
+	cDarkGray = 90
+)
+
+var consoleBufPool = sync.Pool{
+	New: func() interface{} {
+		return bytes.NewBuffer(make([]byte, 0, 100))
+	},
+}
+
+// ConsoleWriter reads a JSON object per write operation and output an
+// optionally colored human readable version on the Out writer.
+type ConsoleWriter struct {
+	Out     io.Writer
+	NoColor bool
+}
+
+func (w ConsoleWriter) Write(p []byte) (n int, err error) {
+	var event map[string]interface{}
+	err = json.Unmarshal(p, &event)
+	if err != nil {
+		return
+	}
+	buf := consoleBufPool.Get().(*bytes.Buffer)
+	defer consoleBufPool.Put(buf)
+	lvlColor := cReset
+	level := "????"
+	if l, ok := event[LevelFieldName].(string); ok {
+		if !w.NoColor {
+			lvlColor = levelColor(l)
+		}
+		level = strings.ToUpper(l)[0:4]
+	}
+	fmt.Fprintf(buf, "%s |%s| %s",
+		colorize(event[TimestampFieldName], cDarkGray, !w.NoColor),
+		colorize(level, lvlColor, !w.NoColor),
+		colorize(event[MessageFieldName], cReset, !w.NoColor))
+	fields := make([]string, 0, len(event))
+	for field := range event {
+		switch field {
+		case LevelFieldName, TimestampFieldName, MessageFieldName:
+			continue
+		}
+		fields = append(fields, field)
+	}
+	sort.Strings(fields)
+	for _, field := range fields {
+		fmt.Fprintf(buf, " %s=", colorize(field, cCyan, !w.NoColor))
+		switch value := event[field].(type) {
+		case string:
+			if needsQuote(value) {
+				buf.WriteString(strconv.Quote(value))
+			} else {
+				buf.WriteString(value)
+			}
+		default:
+			fmt.Fprint(buf, value)
+		}
+	}
+	buf.WriteByte('\n')
+	buf.WriteTo(w.Out)
+	n = len(p)
+	return
+}
+
+func colorize(s interface{}, color int, enabled bool) string {
+	if !enabled {
+		return fmt.Sprintf("%v", s)
+	}
+	return fmt.Sprintf("\x1b[%dm%v\x1b[0m", color, s)
+}
+
+func levelColor(level string) int {
+	switch level {
+	case "debug":
+		return cMagenta
+	case "info":
+		return cGreen
+	case "warn":
+		return cYellow
+	case "error", "fatal", "panic":
+		return cRed
+	default:
+		return cReset
+	}
+}
+
+func needsQuote(s string) bool {
+	for i := range s {
+		if s[i] < 0x20 || s[i] > 0x7e || s[i] == ' ' || s[i] == '\\' || s[i] == '"' {
+			return true
+		}
+	}
+	return false
+}

context.go

@@ -1,6 +1,11 @@
 package zerolog
 
-import "time"
+import (
+	"io/ioutil"
+	"time"
+
+	"github.com/rs/zerolog/internal/json"
+)
 
 // Context configures a new sub-logger with contextual fields.
 type Context struct {
@@ -12,108 +17,244 @@ func (c Context) Logger() Logger {
 	return c.l
 }
 
+// Fields is a helper function to use a map to set fields using type assertion.
+func (c Context) Fields(fields map[string]interface{}) Context {
+	c.l.context = appendFields(c.l.context, fields)
+	return c
+}
+
 // Dict adds the field key with the dict to the logger context.
 func (c Context) Dict(key string, dict *Event) Context {
 	dict.buf = append(dict.buf, '}')
-	c.l.context = append(appendKey(c.l.context, key), dict.buf...)
+	c.l.context = append(json.AppendKey(c.l.context, key), dict.buf...)
 	eventPool.Put(dict)
 	return c
 }
 
+// Array adds the field key with an array to the event context.
+// Use zerolog.Arr() to create the array or pass a type that
+// implement the LogArrayMarshaler interface.
+func (c Context) Array(key string, arr LogArrayMarshaler) Context {
+	c.l.context = json.AppendKey(c.l.context, key)
+	if arr, ok := arr.(*Array); ok {
+		c.l.context = arr.write(c.l.context)
+		return c
+	}
+	var a *Array
+	if aa, ok := arr.(*Array); ok {
+		a = aa
+	} else {
+		a = Arr()
+		arr.MarshalZerologArray(a)
+	}
+	c.l.context = a.write(c.l.context)
+	return c
+}
+
+// Object marshals an object that implement the LogObjectMarshaler interface.
+func (c Context) Object(key string, obj LogObjectMarshaler) Context {
+	e := newEvent(levelWriterAdapter{ioutil.Discard}, 0, true)
+	e.Object(key, obj)
+	e.buf[0] = ',' // A new event starts as an object, we want to embed it.
+	c.l.context = append(c.l.context, e.buf...)
+	eventPool.Put(e)
+	return c
+}
+
 // Str adds the field key with val as a string to the logger context.
 func (c Context) Str(key, val string) Context {
-	c.l.context = appendString(c.l.context, key, val)
+	c.l.context = json.AppendString(json.AppendKey(c.l.context, key), val)
+	return c
+}
+
+// Strs adds the field key with val as a string to the logger context.
+func (c Context) Strs(key string, vals []string) Context {
+	c.l.context = json.AppendStrings(json.AppendKey(c.l.context, key), vals)
+	return c
+}
+
+// Bytes adds the field key with val as a []byte to the logger context.
+func (c Context) Bytes(key string, val []byte) Context {
+	c.l.context = json.AppendBytes(json.AppendKey(c.l.context, key), val)
 	return c
 }
 
 // AnErr adds the field key with err as a string to the logger context.
 func (c Context) AnErr(key string, err error) Context {
-	c.l.context = appendErrorKey(c.l.context, key, err)
+	if err != nil {
+		c.l.context = json.AppendError(json.AppendKey(c.l.context, key), err)
+	}
+	return c
+}
+
+// Errs adds the field key with errs as an array of strings to the logger context.
+func (c Context) Errs(key string, errs []error) Context {
+	c.l.context = json.AppendErrors(json.AppendKey(c.l.context, key), errs)
 	return c
 }
 
 // Err adds the field "error" with err as a string to the logger context.
 // To customize the key name, change zerolog.ErrorFieldName.
 func (c Context) Err(err error) Context {
-	c.l.context = appendError(c.l.context, err)
+	if err != nil {
+		c.l.context = json.AppendError(json.AppendKey(c.l.context, ErrorFieldName), err)
+	}
 	return c
 }
 
-// Bool adds the field key with val as a Boolean to the logger context.
+// Bool adds the field key with val as a bool to the logger context.
 func (c Context) Bool(key string, b bool) Context {
-	c.l.context = appendBool(c.l.context, key, b)
+	c.l.context = json.AppendBool(json.AppendKey(c.l.context, key), b)
+	return c
+}
+
+// Bools adds the field key with val as a []bool to the logger context.
+func (c Context) Bools(key string, b []bool) Context {
+	c.l.context = json.AppendBools(json.AppendKey(c.l.context, key), b)
 	return c
 }
 
 // Int adds the field key with i as a int to the logger context.
 func (c Context) Int(key string, i int) Context {
-	c.l.context = appendInt(c.l.context, key, i)
+	c.l.context = json.AppendInt(json.AppendKey(c.l.context, key), i)
+	return c
+}
+
+// Ints adds the field key with i as a []int to the logger context.
+func (c Context) Ints(key string, i []int) Context {
+	c.l.context = json.AppendInts(json.AppendKey(c.l.context, key), i)
 	return c
 }
 
 // Int8 adds the field key with i as a int8 to the logger context.
 func (c Context) Int8(key string, i int8) Context {
-	c.l.context = appendInt8(c.l.context, key, i)
+	c.l.context = json.AppendInt8(json.AppendKey(c.l.context, key), i)
+	return c
+}
+
+// Ints8 adds the field key with i as a []int8 to the logger context.
+func (c Context) Ints8(key string, i []int8) Context {
+	c.l.context = json.AppendInts8(json.AppendKey(c.l.context, key), i)
 	return c
 }
 
 // Int16 adds the field key with i as a int16 to the logger context.
 func (c Context) Int16(key string, i int16) Context {
-	c.l.context = appendInt16(c.l.context, key, i)
+	c.l.context = json.AppendInt16(json.AppendKey(c.l.context, key), i)
+	return c
+}
+
+// Ints16 adds the field key with i as a []int16 to the logger context.
+func (c Context) Ints16(key string, i []int16) Context {
+	c.l.context = json.AppendInts16(json.AppendKey(c.l.context, key), i)
 	return c
 }
 
 // Int32 adds the field key with i as a int32 to the logger context.
 func (c Context) Int32(key string, i int32) Context {
-	c.l.context = appendInt32(c.l.context, key, i)
+	c.l.context = json.AppendInt32(json.AppendKey(c.l.context, key), i)
+	return c
+}
+
+// Ints32 adds the field key with i as a []int32 to the logger context.
+func (c Context) Ints32(key string, i []int32) Context {
+	c.l.context = json.AppendInts32(json.AppendKey(c.l.context, key), i)
 	return c
 }
 
 // Int64 adds the field key with i as a int64 to the logger context.
 func (c Context) Int64(key string, i int64) Context {
-	c.l.context = appendInt64(c.l.context, key, i)
+	c.l.context = json.AppendInt64(json.AppendKey(c.l.context, key), i)
+	return c
+}
+
+// Ints64 adds the field key with i as a []int64 to the logger context.
+func (c Context) Ints64(key string, i []int64) Context {
+	c.l.context = json.AppendInts64(json.AppendKey(c.l.context, key), i)
 	return c
 }
 
 // Uint adds the field key with i as a uint to the logger context.
 func (c Context) Uint(key string, i uint) Context {
-	c.l.context = appendUint(c.l.context, key, i)
+	c.l.context = json.AppendUint(json.AppendKey(c.l.context, key), i)
+	return c
+}
+
+// Uints adds the field key with i as a []uint to the logger context.
+func (c Context) Uints(key string, i []uint) Context {
+	c.l.context = json.AppendUints(json.AppendKey(c.l.context, key), i)
 	return c
 }
 
 // Uint8 adds the field key with i as a uint8 to the logger context.
 func (c Context) Uint8(key string, i uint8) Context {
-	c.l.context = appendUint8(c.l.context, key, i)
+	c.l.context = json.AppendUint8(json.AppendKey(c.l.context, key), i)
+	return c
+}
+
+// Uints8 adds the field key with i as a []uint8 to the logger context.
+func (c Context) Uints8(key string, i []uint8) Context {
+	c.l.context = json.AppendUints8(json.AppendKey(c.l.context, key), i)
 	return c
 }
 
 // Uint16 adds the field key with i as a uint16 to the logger context.
 func (c Context) Uint16(key string, i uint16) Context {
-	c.l.context = appendUint16(c.l.context, key, i)
+	c.l.context = json.AppendUint16(json.AppendKey(c.l.context, key), i)
+	return c
+}
+
+// Uints16 adds the field key with i as a []uint16 to the logger context.
+func (c Context) Uints16(key string, i []uint16) Context {
+	c.l.context = json.AppendUints16(json.AppendKey(c.l.context, key), i)
 	return c
 }
 
 // Uint32 adds the field key with i as a uint32 to the logger context.
 func (c Context) Uint32(key string, i uint32) Context {
-	c.l.context = appendUint32(c.l.context, key, i)
+	c.l.context = json.AppendUint32(json.AppendKey(c.l.context, key), i)
+	return c
+}
+
+// Uints32 adds the field key with i as a []uint32 to the logger context.
+func (c Context) Uints32(key string, i []uint32) Context {
+	c.l.context = json.AppendUints32(json.AppendKey(c.l.context, key), i)
 	return c
 }
 
 // Uint64 adds the field key with i as a uint64 to the logger context.
 func (c Context) Uint64(key string, i uint64) Context {
-	c.l.context = appendUint64(c.l.context, key, i)
+	c.l.context = json.AppendUint64(json.AppendKey(c.l.context, key), i)
+	return c
+}
+
+// Uints64 adds the field key with i as a []uint64 to the logger context.
+func (c Context) Uints64(key string, i []uint64) Context {
+	c.l.context = json.AppendUints64(json.AppendKey(c.l.context, key), i)
 	return c
 }
 
 // Float32 adds the field key with f as a float32 to the logger context.
 func (c Context) Float32(key string, f float32) Context {
-	c.l.context = appendFloat32(c.l.context, key, f)
+	c.l.context = json.AppendFloat32(json.AppendKey(c.l.context, key), f)
+	return c
+}
+
+// Floats32 adds the field key with f as a []float32 to the logger context.
+func (c Context) Floats32(key string, f []float32) Context {
+	c.l.context = json.AppendFloats32(json.AppendKey(c.l.context, key), f)
 	return c
 }
 
 // Float64 adds the field key with f as a float64 to the logger context.
 func (c Context) Float64(key string, f float64) Context {
-	c.l.context = appendFloat64(c.l.context, key, f)
+	c.l.context = json.AppendFloat64(json.AppendKey(c.l.context, key), f)
+	return c
+}
+
+// Floats64 adds the field key with f as a []float64 to the logger context.
+func (c Context) Floats64(key string, f []float64) Context {
+	c.l.context = json.AppendFloats64(json.AppendKey(c.l.context, key), f)
 	return c
 }
 
@@ -130,18 +271,30 @@ func (c Context) Timestamp() Context {
 
 // Time adds the field key with t formated as string using zerolog.TimeFieldFormat.
 func (c Context) Time(key string, t time.Time) Context {
-	c.l.context = appendTime(c.l.context, key, t)
+	c.l.context = json.AppendTime(json.AppendKey(c.l.context, key), t, TimeFieldFormat)
+	return c
+}
+
+// Times adds the field key with t formated as string using zerolog.TimeFieldFormat.
+func (c Context) Times(key string, t []time.Time) Context {
+	c.l.context = json.AppendTimes(json.AppendKey(c.l.context, key), t, TimeFieldFormat)
 	return c
 }
 
 // Dur adds the fields key with d divided by unit and stored as a float.
 func (c Context) Dur(key string, d time.Duration) Context {
-	c.l.context = appendDuration(c.l.context, key, d)
+	c.l.context = json.AppendDuration(json.AppendKey(c.l.context, key), d, DurationFieldUnit, DurationFieldInteger)
+	return c
+}
+
+// Durs adds the fields key with d divided by unit and stored as a float.
+func (c Context) Durs(key string, d []time.Duration) Context {
+	c.l.context = json.AppendDurations(json.AppendKey(c.l.context, key), d, DurationFieldUnit, DurationFieldInteger)
 	return c
 }
 
 // Interface adds the field key with obj marshaled using reflection.
 func (c Context) Interface(key string, i interface{}) Context {
-	c.l.context = appendInterface(c.l.context, key, i)
+	c.l.context = json.AppendInterface(json.AppendKey(c.l.context, key), i)
 	return c
 }

ctx.go

@@ -5,25 +5,42 @@ import (
 	"io/ioutil"
 )
 
-var disabledLogger = New(ioutil.Discard).Level(Disabled)
+var disabledLogger *Logger
+
+func init() {
+	l := New(ioutil.Discard).Level(Disabled)
+	disabledLogger = &l
+}
 
 type ctxKey struct{}
 
-// WithContext returns a copy of ctx with l associated.
+// WithContext returns a copy of ctx with l associated. If an instance of Logger
+// is already in the context, the pointer to this logger is updated with l.
+//
+// For instance, to add a field to an existing logger in the context, use this
+// notation:
+//
+//     ctx := r.Context()
+//     l := zerolog.Ctx(ctx)
+//     ctx = l.With().Str("foo", "bar").WithContext(ctx)
 func (l Logger) WithContext(ctx context.Context) context.Context {
 	if lp, ok := ctx.Value(ctxKey{}).(*Logger); ok {
 		// Update existing pointer.
 		*lp = l
 		return ctx
 	}
+	if l.level == Disabled {
+		// Do not store disabled logger.
+		return ctx
+	}
 	return context.WithValue(ctx, ctxKey{}, &l)
 }
 
 // Ctx returns the Logger associated with the ctx. If no logger
 // is associated, a disabled logger is returned.
-func Ctx(ctx context.Context) Logger {
+func Ctx(ctx context.Context) *Logger {
 	if l, ok := ctx.Value(ctxKey{}).(*Logger); ok {
-		return *l
+		return l
 	}
 	return disabledLogger
 }

ctx_test.go

@@ -11,7 +11,7 @@ func TestCtx(t *testing.T) {
 	log := New(ioutil.Discard)
 	ctx := log.WithContext(context.Background())
 	log2 := Ctx(ctx)
-	if !reflect.DeepEqual(log, log2) {
+	if !reflect.DeepEqual(log, *log2) {
 		t.Error("Ctx did not return the expected logger")
 	}
 
@@ -19,12 +19,29 @@ func TestCtx(t *testing.T) {
 	log = log.Level(InfoLevel)
 	ctx = log.WithContext(ctx)
 	log2 = Ctx(ctx)
-	if !reflect.DeepEqual(log, log2) {
+	if !reflect.DeepEqual(log, *log2) {
 		t.Error("Ctx did not return the expected logger")
 	}
 
 	log2 = Ctx(context.Background())
-	if !reflect.DeepEqual(log2, disabledLogger) {
+	if log2 != disabledLogger {
 		t.Error("Ctx did not return the expected logger")
 	}
 }
+
+func TestCtxDisabled(t *testing.T) {
+	ctx := disabledLogger.WithContext(context.Background())
+	if ctx != context.Background() {
+		t.Error("WithContext stored a disabled logger")
+	}
+
+	ctx = New(ioutil.Discard).WithContext(ctx)
+	if reflect.DeepEqual(Ctx(ctx), disabledLogger) {
+		t.Error("WithContext did not store logger")
+	}
+
+	ctx = disabledLogger.WithContext(ctx)
+	if !reflect.DeepEqual(Ctx(ctx), disabledLogger) {
+		t.Error("WithContext did not update logger pointer with disabled logger")
+	}
+}

event.go

@@ -6,6 +6,8 @@ import (
 	"os"
 	"sync"
 	"time"
+
+	"github.com/rs/zerolog/internal/json"
 )
 
 var eventPool = &sync.Pool{
@@ -19,11 +21,23 @@ var eventPool = &sync.Pool{
 // Event represents a log event. It is instanced by one of the level method of
 // Logger and finalized by the Msg or Msgf method.
 type Event struct {
-	buf     []byte
-	w       LevelWriter
-	level   Level
-	enabled bool
-	done    func(msg string)
+	buf   []byte
+	w     LevelWriter
+	level Level
+	done  func(msg string)
+	h     []Hook
+}
+
+// LogObjectMarshaler provides a strongly-typed and encoding-agnostic interface
+// to be implemented by types used with Event/Context's Object methods.
+type LogObjectMarshaler interface {
+	MarshalZerologObject(e *Event)
+}
+
+// LogArrayMarshaler provides a strongly-typed and encoding-agnostic interface
+// to be implemented by types used with Event/Context's Array methods.
+type LogArrayMarshaler interface {
+	MarshalZerologArray(a *Array)
 }
 
 func newEvent(w LevelWriter, level Level, enabled bool) *Event {
@@ -32,15 +46,15 @@ func newEvent(w LevelWriter, level Level, enabled bool) *Event {
 	}
 	e := eventPool.Get().(*Event)
 	e.buf = e.buf[:1]
+	e.h = e.h[:0]
 	e.buf[0] = '{'
 	e.w = w
 	e.level = level
-	e.enabled = true
 	return e
 }
 
 func (e *Event) write() (err error) {
-	if !e.enabled {
+	if e == nil {
 		return nil
 	}
 	e.buf = append(e.buf, '}', '\n')
@@ -52,7 +66,7 @@ func (e *Event) write() (err error) {
 // Enabled return false if the *Event is going to be filtered out by
 // log level or sampling.
 func (e *Event) Enabled() bool {
-	return e.enabled
+	return e != nil
 }
 
 // Msg sends the *Event with msg added as the message field if not empty.
@@ -60,11 +74,19 @@ func (e *Event) Enabled() bool {
 // NOTICE: once this method is called, the *Event should be disposed.
 // Calling Msg twice can have unexpected result.
 func (e *Event) Msg(msg string) {
-	if !e.enabled {
+	if e == nil {
 		return
 	}
+	if len(e.h) > 0 {
+		e.h[0].Run(e, e.level, msg)
+		if len(e.h) > 1 {
+			for _, hook := range e.h[1:] {
+				hook.Run(e, e.level, msg)
+			}
+		}
+	}
 	if msg != "" {
-		e.buf = appendString(e.buf, MessageFieldName, msg)
+		e.buf = json.AppendString(json.AppendKey(e.buf, MessageFieldName), msg)
 	}
 	if e.done != nil {
 		defer e.done(msg)
@@ -79,28 +101,28 @@ func (e *Event) Msg(msg string) {
 // NOTICE: once this methid is called, the *Event should be disposed.
 // Calling Msg twice can have unexpected result.
 func (e *Event) Msgf(format string, v ...interface{}) {
-	if !e.enabled {
+	if e == nil {
 		return
 	}
-	msg := fmt.Sprintf(format, v...)
-	if msg != "" {
-		e.buf = appendString(e.buf, MessageFieldName, msg)
-	}
-	if e.done != nil {
-		defer e.done(msg)
-	}
-	if err := e.write(); err != nil {
-		fmt.Fprintf(os.Stderr, "zerolog: could not write event: %v", err)
+	e.Msg(fmt.Sprintf(format, v...))
+}
+
+// Fields is a helper function to use a map to set fields using type assertion.
+func (e *Event) Fields(fields map[string]interface{}) *Event {
+	if e == nil {
+		return e
 	}
+	e.buf = appendFields(e.buf, fields)
+	return e
 }
 
 // Dict adds the field key with a dict to the event context.
 // Use zerolog.Dict() to create the dictionary.
 func (e *Event) Dict(key string, dict *Event) *Event {
-	if !e.enabled {
+	if e == nil {
 		return e
 	}
-	e.buf = append(append(appendKey(e.buf, key), dict.buf...), '}')
+	e.buf = append(append(json.AppendKey(e.buf, key), dict.buf...), '}')
 	eventPool.Put(dict)
 	return e
 }
@@ -112,22 +134,98 @@ func Dict() *Event {
 	return newEvent(levelWriterAdapter{ioutil.Discard}, 0, true)
 }
 
-// Str adds the field key with val as a string to the *Event context.
-func (e *Event) Str(key, val string) *Event {
-	if !e.enabled {
+// Array adds the field key with an array to the event context.
+// Use zerolog.Arr() to create the array or pass a type that
+// implement the LogArrayMarshaler interface.
+func (e *Event) Array(key string, arr LogArrayMarshaler) *Event {
+	if e == nil {
 		return e
 	}
-	e.buf = appendString(e.buf, key, val)
+	e.buf = json.AppendKey(e.buf, key)
+	var a *Array
+	if aa, ok := arr.(*Array); ok {
+		a = aa
+	} else {
+		a = Arr()
+		arr.MarshalZerologArray(a)
+	}
+	e.buf = a.write(e.buf)
+	return e
+}
+
+func (e *Event) appendObject(obj LogObjectMarshaler) {
+	pos := len(e.buf)
+	obj.MarshalZerologObject(e)
+	if pos < len(e.buf) {
+		// As MarshalZerologObject will use event API, the first field will be
+		// preceded by a comma. If at least one field has been added (buf grew),
+		// we replace this coma by the opening bracket.
+		e.buf[pos] = '{'
+	} else {
+		e.buf = append(e.buf, '{')
+	}
+	e.buf = append(e.buf, '}')
+}
+
+// Object marshals an object that implement the LogObjectMarshaler interface.
+func (e *Event) Object(key string, obj LogObjectMarshaler) *Event {
+	if e == nil {
+		return e
+	}
+	e.buf = json.AppendKey(e.buf, key)
+	e.appendObject(obj)
+	return e
+}
+
+// Str adds the field key with val as a string to the *Event context.
+func (e *Event) Str(key, val string) *Event {
+	if e == nil {
+		return e
+	}
+	e.buf = json.AppendString(json.AppendKey(e.buf, key), val)
+	return e
+}
+
+// Strs adds the field key with vals as a []string to the *Event context.
+func (e *Event) Strs(key string, vals []string) *Event {
+	if e == nil {
+		return e
+	}
+	e.buf = json.AppendStrings(json.AppendKey(e.buf, key), vals)
+	return e
+}
+
+// Bytes adds the field key with val as a string to the *Event context.
+//
+// Runes outside of normal ASCII ranges will be hex-encoded in the resulting
+// JSON.
+func (e *Event) Bytes(key string, val []byte) *Event {
+	if e == nil {
+		return e
+	}
+	e.buf = json.AppendBytes(json.AppendKey(e.buf, key), val)
 	return e
 }
 
 // AnErr adds the field key with err as a string to the *Event context.
 // If err is nil, no field is added.
 func (e *Event) AnErr(key string, err error) *Event {
-	if !e.enabled {
+	if e == nil {
 		return e
 	}
-	e.buf = appendErrorKey(e.buf, key, err)
+	if err != nil {
+		e.buf = json.AppendError(json.AppendKey(e.buf, key), err)
+	}
+	return e
+}
+
+// Errs adds the field key with errs as an array of strings to the *Event context.
+// If err is nil, no field is added.
+func (e *Event) Errs(key string, errs []error) *Event {
+	if e == nil {
+		return e
+	}
+	e.buf = json.AppendErrors(json.AppendKey(e.buf, key), errs)
 	return e
 }
 
@@ -135,146 +233,274 @@ func (e *Event) AnErr(key string, err error) *Event {
 // If err is nil, no field is added.
 // To customize the key name, change zerolog.ErrorFieldName.
 func (e *Event) Err(err error) *Event {
-	if !e.enabled {
+	if e == nil {
 		return e
 	}
-	e.buf = appendError(e.buf, err)
+	if err != nil {
+		e.buf = json.AppendError(json.AppendKey(e.buf, ErrorFieldName), err)
+	}
 	return e
 }
 
-// Bool adds the field key with val as a Boolean to the *Event context.
+// Bool adds the field key with val as a bool to the *Event context.
 func (e *Event) Bool(key string, b bool) *Event {
-	if !e.enabled {
+	if e == nil {
 		return e
 	}
-	e.buf = appendBool(e.buf, key, b)
+	e.buf = json.AppendBool(json.AppendKey(e.buf, key), b)
+	return e
+}
+
+// Bools adds the field key with val as a []bool to the *Event context.
+func (e *Event) Bools(key string, b []bool) *Event {
+	if e == nil {
+		return e
+	}
+	e.buf = json.AppendBools(json.AppendKey(e.buf, key), b)
 	return e
 }
 
 // Int adds the field key with i as a int to the *Event context.
 func (e *Event) Int(key string, i int) *Event {
-	if !e.enabled {
+	if e == nil {
 		return e
 	}
-	e.buf = appendInt(e.buf, key, i)
+	e.buf = json.AppendInt(json.AppendKey(e.buf, key), i)
+	return e
+}
+
+// Ints adds the field key with i as a []int to the *Event context.
+func (e *Event) Ints(key string, i []int) *Event {
+	if e == nil {
+		return e
+	}
+	e.buf = json.AppendInts(json.AppendKey(e.buf, key), i)
 	return e
 }
 
 // Int8 adds the field key with i as a int8 to the *Event context.
 func (e *Event) Int8(key string, i int8) *Event {
-	if !e.enabled {
+	if e == nil {
 		return e
 	}
-	e.buf = appendInt8(e.buf, key, i)
+	e.buf = json.AppendInt8(json.AppendKey(e.buf, key), i)
+	return e
+}
+
+// Ints8 adds the field key with i as a []int8 to the *Event context.
+func (e *Event) Ints8(key string, i []int8) *Event {
+	if e == nil {
+		return e
+	}
+	e.buf = json.AppendInts8(json.AppendKey(e.buf, key), i)
 	return e
 }
 
 // Int16 adds the field key with i as a int16 to the *Event context.
 func (e *Event) Int16(key string, i int16) *Event {
-	if !e.enabled {
+	if e == nil {
 		return e
 	}
-	e.buf = appendInt16(e.buf, key, i)
+	e.buf = json.AppendInt16(json.AppendKey(e.buf, key), i)
+	return e
+}
+
+// Ints16 adds the field key with i as a []int16 to the *Event context.
+func (e *Event) Ints16(key string, i []int16) *Event {
+	if e == nil {
+		return e
+	}
+	e.buf = json.AppendInts16(json.AppendKey(e.buf, key), i)
 	return e
 }
 
 // Int32 adds the field key with i as a int32 to the *Event context.
 func (e *Event) Int32(key string, i int32) *Event {
-	if !e.enabled {
+	if e == nil {
 		return e
 	}
-	e.buf = appendInt32(e.buf, key, i)
+	e.buf = json.AppendInt32(json.AppendKey(e.buf, key), i)
+	return e
+}
+
+// Ints32 adds the field key with i as a []int32 to the *Event context.
+func (e *Event) Ints32(key string, i []int32) *Event {
+	if e == nil {
+		return e
+	}
+	e.buf = json.AppendInts32(json.AppendKey(e.buf, key), i)
 	return e
 }
 
 // Int64 adds the field key with i as a int64 to the *Event context.
 func (e *Event) Int64(key string, i int64) *Event {
-	if !e.enabled {
+	if e == nil {
 		return e
 	}
-	e.buf = appendInt64(e.buf, key, i)
+	e.buf = json.AppendInt64(json.AppendKey(e.buf, key), i)
+	return e
+}
+
+// Ints64 adds the field key with i as a []int64 to the *Event context.
+func (e *Event) Ints64(key string, i []int64) *Event {
+	if e == nil {
+		return e
+	}
+	e.buf = json.AppendInts64(json.AppendKey(e.buf, key), i)
 	return e
 }
 
 // Uint adds the field key with i as a uint to the *Event context.
 func (e *Event) Uint(key string, i uint) *Event {
-	if !e.enabled {
+	if e == nil {
 		return e
 	}
-	e.buf = appendUint(e.buf, key, i)
+	e.buf = json.AppendUint(json.AppendKey(e.buf, key), i)
+	return e
+}
+
+// Uints adds the field key with i as a []int to the *Event context.
+func (e *Event) Uints(key string, i []uint) *Event {
+	if e == nil {
+		return e
+	}
+	e.buf = json.AppendUints(json.AppendKey(e.buf, key), i)
 	return e
 }
 
 // Uint8 adds the field key with i as a uint8 to the *Event context.
 func (e *Event) Uint8(key string, i uint8) *Event {
-	if !e.enabled {
+	if e == nil {
 		return e
 	}
-	e.buf = appendUint8(e.buf, key, i)
+	e.buf = json.AppendUint8(json.AppendKey(e.buf, key), i)
+	return e
+}
+
+// Uints8 adds the field key with i as a []int8 to the *Event context.
+func (e *Event) Uints8(key string, i []uint8) *Event {
+	if e == nil {
+		return e
+	}
+	e.buf = json.AppendUints8(json.AppendKey(e.buf, key), i)
 	return e
 }
 
 // Uint16 adds the field key with i as a uint16 to the *Event context.
 func (e *Event) Uint16(key string, i uint16) *Event {
-	if !e.enabled {
+	if e == nil {
 		return e
 	}
-	e.buf = appendUint16(e.buf, key, i)
+	e.buf = json.AppendUint16(json.AppendKey(e.buf, key), i)
+	return e
+}
+
+// Uints16 adds the field key with i as a []int16 to the *Event context.
+func (e *Event) Uints16(key string, i []uint16) *Event {
+	if e == nil {
+		return e
+	}
+	e.buf = json.AppendUints16(json.AppendKey(e.buf, key), i)
 	return e
 }
 
 // Uint32 adds the field key with i as a uint32 to the *Event context.
 func (e *Event) Uint32(key string, i uint32) *Event {
-	if !e.enabled {
+	if e == nil {
 		return e
 	}
-	e.buf = appendUint32(e.buf, key, i)
+	e.buf = json.AppendUint32(json.AppendKey(e.buf, key), i)
+	return e
+}
+
+// Uints32 adds the field key with i as a []int32 to the *Event context.
+func (e *Event) Uints32(key string, i []uint32) *Event {
+	if e == nil {
+		return e
+	}
+	e.buf = json.AppendUints32(json.AppendKey(e.buf, key), i)
 	return e
 }
 
 // Uint64 adds the field key with i as a uint64 to the *Event context.
 func (e *Event) Uint64(key string, i uint64) *Event {
-	if !e.enabled {
+	if e == nil {
 		return e
 	}
-	e.buf = appendUint64(e.buf, key, i)
+	e.buf = json.AppendUint64(json.AppendKey(e.buf, key), i)
+	return e
+}
+
+// Uints64 adds the field key with i as a []int64 to the *Event context.
+func (e *Event) Uints64(key string, i []uint64) *Event {
+	if e == nil {
+		return e
+	}
+	e.buf = json.AppendUints64(json.AppendKey(e.buf, key), i)
 	return e
 }
 
 // Float32 adds the field key with f as a float32 to the *Event context.
 func (e *Event) Float32(key string, f float32) *Event {
-	if !e.enabled {
+	if e == nil {
 		return e
 	}
-	e.buf = appendFloat32(e.buf, key, f)
+	e.buf = json.AppendFloat32(json.AppendKey(e.buf, key), f)
+	return e
+}
+
+// Floats32 adds the field key with f as a []float32 to the *Event context.
+func (e *Event) Floats32(key string, f []float32) *Event {
+	if e == nil {
+		return e
+	}
+	e.buf = json.AppendFloats32(json.AppendKey(e.buf, key), f)
 	return e
 }
 
 // Float64 adds the field key with f as a float64 to the *Event context.
 func (e *Event) Float64(key string, f float64) *Event {
-	if !e.enabled {
+	if e == nil {
 		return e
 	}
-	e.buf = appendFloat64(e.buf, key, f)
+	e.buf = json.AppendFloat64(json.AppendKey(e.buf, key), f)
+	return e
+}
+
+// Floats64 adds the field key with f as a []float64 to the *Event context.
+func (e *Event) Floats64(key string, f []float64) *Event {
+	if e == nil {
+		return e
+	}
+	e.buf = json.AppendFloats64(json.AppendKey(e.buf, key), f)
 	return e
 }
 
 // Timestamp adds the current local time as UNIX timestamp to the *Event context with the "time" key.
 // To customize the key name, change zerolog.TimestampFieldName.
 func (e *Event) Timestamp() *Event {
-	if !e.enabled {
+	if e == nil {
 		return e
 	}
-	e.buf = appendTimestamp(e.buf)
+	e.buf = json.AppendTime(json.AppendKey(e.buf, TimestampFieldName), TimestampFunc(), TimeFieldFormat)
 	return e
 }
 
 // Time adds the field key with t formated as string using zerolog.TimeFieldFormat.
 func (e *Event) Time(key string, t time.Time) *Event {
-	if !e.enabled {
+	if e == nil {
 		return e
 	}
-	e.buf = appendTime(e.buf, key, t)
+	e.buf = json.AppendTime(json.AppendKey(e.buf, key), t, TimeFieldFormat)
+	return e
+}
+
+// Times adds the field key with t formated as string using zerolog.TimeFieldFormat.
+func (e *Event) Times(key string, t []time.Time) *Event {
+	if e == nil {
+		return e
+	}
+	e.buf = json.AppendTimes(json.AppendKey(e.buf, key), t, TimeFieldFormat)
 	return e
 }
 
@@ -282,10 +508,21 @@ func (e *Event) Time(key string, t time.Time) *Event {
 // If zerolog.DurationFieldInteger is true, durations are rendered as integer
 // instead of float.
 func (e *Event) Dur(key string, d time.Duration) *Event {
-	if !e.enabled {
+	if e == nil {
 		return e
 	}
-	e.buf = appendDuration(e.buf, key, d)
+	e.buf = json.AppendDuration(json.AppendKey(e.buf, key), d, DurationFieldUnit, DurationFieldInteger)
+	return e
+}
+
+// Durs adds the field key with duration d stored as zerolog.DurationFieldUnit.
+// If zerolog.DurationFieldInteger is true, durations are rendered as integer
+// instead of float.
+func (e *Event) Durs(key string, d []time.Duration) *Event {
+	if e == nil {
+		return e
+	}
+	e.buf = json.AppendDurations(json.AppendKey(e.buf, key), d, DurationFieldUnit, DurationFieldInteger)
 	return e
 }
 
@@ -293,22 +530,25 @@ func (e *Event) Dur(key string, d time.Duration) *Event {
 // If time t is not greater than start, duration will be 0.
 // Duration format follows the same principle as Dur().
 func (e *Event) TimeDiff(key string, t time.Time, start time.Time) *Event {
-	if !e.enabled {
+	if e == nil {
 		return e
 	}
 	var d time.Duration
 	if t.After(start) {
 		d = t.Sub(start)
 	}
-	e.buf = appendDuration(e.buf, key, d)
+	e.buf = json.AppendDuration(json.AppendKey(e.buf, key), d, DurationFieldUnit, DurationFieldInteger)
 	return e
 }
 
 // Interface adds the field key with i marshaled using reflection.
 func (e *Event) Interface(key string, i interface{}) *Event {
-	if !e.enabled {
+	if e == nil {
 		return e
 	}
-	e.buf = appendInterface(e.buf, key, i)
+	if obj, ok := i.(LogObjectMarshaler); ok {
+		return e.Object(key, obj)
+	}
+	e.buf = json.AppendInterface(json.AppendKey(e.buf, key), i)
 	return e
 }

field.go

@@ -1,109 +0,0 @@
-package zerolog
-
-import (
-	"encoding/json"
-	"fmt"
-	"strconv"
-	"time"
-)
-
-func appendKey(dst []byte, key string) []byte {
-	if len(dst) > 1 {
-		dst = append(dst, ',')
-	}
-	dst = appendJSONString(dst, key)
-	return append(dst, ':')
-}
-
-func appendString(dst []byte, key, val string) []byte {
-	return appendJSONString(appendKey(dst, key), val)
-}
-
-func appendErrorKey(dst []byte, key string, err error) []byte {
-	if err == nil {
-		return dst
-	}
-	return appendJSONString(appendKey(dst, key), err.Error())
-}
-
-func appendError(dst []byte, err error) []byte {
-	return appendErrorKey(dst, ErrorFieldName, err)
-}
-
-func appendBool(dst []byte, key string, val bool) []byte {
-	return strconv.AppendBool(appendKey(dst, key), val)
-}
-
-func appendInt(dst []byte, key string, val int) []byte {
-	return strconv.AppendInt(appendKey(dst, key), int64(val), 10)
-}
-
-func appendInt8(dst []byte, key string, val int8) []byte {
-	return strconv.AppendInt(appendKey(dst, key), int64(val), 10)
-}
-
-func appendInt16(dst []byte, key string, val int16) []byte {
-	return strconv.AppendInt(appendKey(dst, key), int64(val), 10)
-}
-
-func appendInt32(dst []byte, key string, val int32) []byte {
-	return strconv.AppendInt(appendKey(dst, key), int64(val), 10)
-}
-
-func appendInt64(dst []byte, key string, val int64) []byte {
-	return strconv.AppendInt(appendKey(dst, key), int64(val), 10)
-}
-
-func appendUint(dst []byte, key string, val uint) []byte {
-	return strconv.AppendUint(appendKey(dst, key), uint64(val), 10)
-}
-
-func appendUint8(dst []byte, key string, val uint8) []byte {
-	return strconv.AppendUint(appendKey(dst, key), uint64(val), 10)
-}
-
-func appendUint16(dst []byte, key string, val uint16) []byte {
-	return strconv.AppendUint(appendKey(dst, key), uint64(val), 10)
-}
-
-func appendUint32(dst []byte, key string, val uint32) []byte {
-	return strconv.AppendUint(appendKey(dst, key), uint64(val), 10)
-}
-
-func appendUint64(dst []byte, key string, val uint64) []byte {
-	return strconv.AppendUint(appendKey(dst, key), uint64(val), 10)
-}
-
-func appendFloat32(dst []byte, key string, val float32) []byte {
-	return strconv.AppendFloat(appendKey(dst, key), float64(val), 'f', -1, 32)
-}
-
-func appendFloat64(dst []byte, key string, val float64) []byte {
-	return strconv.AppendFloat(appendKey(dst, key), float64(val), 'f', -1, 32)
-}
-
-func appendTime(dst []byte, key string, t time.Time) []byte {
-	if TimeFieldFormat == "" {
-		return appendInt64(dst, key, t.Unix())
-	}
-	return append(t.AppendFormat(append(appendKey(dst, key), '"'), TimeFieldFormat), '"')
-}
-
-func appendTimestamp(dst []byte) []byte {
-	return appendTime(dst, TimestampFieldName, TimestampFunc())
-}
-
-func appendDuration(dst []byte, key string, d time.Duration) []byte {
-	if DurationFieldInteger {
-		return appendInt64(dst, key, int64(d/DurationFieldUnit))
-	}
-	return appendFloat64(dst, key, float64(d)/float64(DurationFieldUnit))
-}
-
-func appendInterface(dst []byte, key string, i interface{}) []byte {
-	marshaled, err := json.Marshal(i)
-	if err != nil {
-		return appendString(dst, key, fmt.Sprintf("marshaling error: %v", err))
-	}
-	return append(appendKey(dst, key), marshaled...)
-}

fields.go

@@ -0,0 +1,96 @@
+package zerolog
+
+import (
+	"sort"
+	"time"
+
+	"github.com/rs/zerolog/internal/json"
+)
+
+func appendFields(dst []byte, fields map[string]interface{}) []byte {
+	keys := make([]string, 0, len(fields))
+	for key := range fields {
+		keys = append(keys, key)
+	}
+	sort.Strings(keys)
+	for _, key := range keys {
+		dst = json.AppendKey(dst, key)
+		switch val := fields[key].(type) {
+		case string:
+			dst = json.AppendString(dst, val)
+		case []byte:
+			dst = json.AppendBytes(dst, val)
+		case error:
+			dst = json.AppendError(dst, val)
+		case []error:
+			dst = json.AppendErrors(dst, val)
+		case bool:
+			dst = json.AppendBool(dst, val)
+		case int:
+			dst = json.AppendInt(dst, val)
+		case int8:
+			dst = json.AppendInt8(dst, val)
+		case int16:
+			dst = json.AppendInt16(dst, val)
+		case int32:
+			dst = json.AppendInt32(dst, val)
+		case int64:
+			dst = json.AppendInt64(dst, val)
+		case uint:
+			dst = json.AppendUint(dst, val)
+		case uint8:
+			dst = json.AppendUint8(dst, val)
+		case uint16:
+			dst = json.AppendUint16(dst, val)
+		case uint32:
+			dst = json.AppendUint32(dst, val)
+		case uint64:
+			dst = json.AppendUint64(dst, val)
+		case float32:
+			dst = json.AppendFloat32(dst, val)
+		case float64:
+			dst = json.AppendFloat64(dst, val)
+		case time.Time:
+			dst = json.AppendTime(dst, val, TimeFieldFormat)
+		case time.Duration:
+			dst = json.AppendDuration(dst, val, DurationFieldUnit, DurationFieldInteger)
+		case []string:
+			dst = json.AppendStrings(dst, val)
+		case []bool:
+			dst = json.AppendBools(dst, val)
+		case []int:
+			dst = json.AppendInts(dst, val)
+		case []int8:
+			dst = json.AppendInts8(dst, val)
+		case []int16:
+			dst = json.AppendInts16(dst, val)
+		case []int32:
+			dst = json.AppendInts32(dst, val)
+		case []int64:
+			dst = json.AppendInts64(dst, val)
+		case []uint:
+			dst = json.AppendUints(dst, val)
+		// case []uint8:
+		// 	dst = appendUints8(dst, val)
+		case []uint16:
+			dst = json.AppendUints16(dst, val)
+		case []uint32:
+			dst = json.AppendUints32(dst, val)
+		case []uint64:
+			dst = json.AppendUints64(dst, val)
+		case []float32:
+			dst = json.AppendFloats32(dst, val)
+		case []float64:
+			dst = json.AppendFloats64(dst, val)
+		case []time.Time:
+			dst = json.AppendTimes(dst, val, TimeFieldFormat)
+		case []time.Duration:
+			dst = json.AppendDurations(dst, val, DurationFieldUnit, DurationFieldInteger)
+		case nil:
+			dst = append(dst, "null"...)
+		default:
+			dst = json.AppendInterface(dst, val)
+		}
+	}
+	return dst
+}

globals.go

@@ -16,9 +16,6 @@ var (
 	// ErrorFieldName is the field name used for error fields.
 	ErrorFieldName = "error"
 
-	// SampleFieldName is the name of the field used to report sampling.
-	SampleFieldName = "sample"
-
 	// TimeFieldFormat defines the time format of the Time field type.
 	// If set to an empty string, the time is formatted as an UNIX timestamp
 	// as integer.
@@ -63,5 +60,5 @@ func DisableSampling(v bool) {
 }
 
 func samplingDisabled() bool {
-	return atomic.LoadUint32(gLevel) == 1
+	return atomic.LoadUint32(disableSampling) == 1
 }

hlog/hlog.go

@@ -5,15 +5,17 @@ import (
 	"context"
 	"net"
 	"net/http"
+	"time"
 
 	"github.com/rs/xid"
 	"github.com/rs/zerolog"
 	"github.com/rs/zerolog/log"
+	"github.com/zenazn/goji/web/mutil"
 )
 
 // FromRequest gets the logger in the request's context.
 // This is a shortcut for log.Ctx(r.Context())
-func FromRequest(r *http.Request) zerolog.Logger {
+func FromRequest(r *http.Request) *zerolog.Logger {
 	return log.Ctx(r.Context())
 }
 
@@ -21,7 +23,10 @@ func FromRequest(r *http.Request) zerolog.Logger {
 func NewHandler(log zerolog.Logger) func(http.Handler) http.Handler {
 	return func(next http.Handler) http.Handler {
 		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-			r = r.WithContext(log.WithContext(r.Context()))
+			// Create a copy of the logger (including internal context slice)
+			// to prevent data race when using UpdateContext.
+			l := log.With().Logger()
+			r = r.WithContext(l.WithContext(r.Context()))
 			next.ServeHTTP(w, r)
 		})
 	}
@@ -33,8 +38,9 @@ func URLHandler(fieldKey string) func(next http.Handler) http.Handler {
 	return func(next http.Handler) http.Handler {
 		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 			log := zerolog.Ctx(r.Context())
-			log = log.With().Str(fieldKey, r.URL.String()).Logger()
-			r = r.WithContext(log.WithContext(r.Context()))
+			log.UpdateContext(func(c zerolog.Context) zerolog.Context {
+				return c.Str(fieldKey, r.URL.String())
+			})
 			next.ServeHTTP(w, r)
 		})
 	}
@@ -46,8 +52,9 @@ func MethodHandler(fieldKey string) func(next http.Handler) http.Handler {
 	return func(next http.Handler) http.Handler {
 		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 			log := zerolog.Ctx(r.Context())
-			log = log.With().Str(fieldKey, r.Method).Logger()
-			r = r.WithContext(log.WithContext(r.Context()))
+			log.UpdateContext(func(c zerolog.Context) zerolog.Context {
+				return c.Str(fieldKey, r.Method)
+			})
 			next.ServeHTTP(w, r)
 		})
 	}
@@ -59,8 +66,9 @@ func RequestHandler(fieldKey string) func(next http.Handler) http.Handler {
 	return func(next http.Handler) http.Handler {
 		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 			log := zerolog.Ctx(r.Context())
-			log = log.With().Str(fieldKey, r.Method+" "+r.URL.String()).Logger()
-			r = r.WithContext(log.WithContext(r.Context()))
+			log.UpdateContext(func(c zerolog.Context) zerolog.Context {
+				return c.Str(fieldKey, r.Method+" "+r.URL.String())
+			})
 			next.ServeHTTP(w, r)
 		})
 	}
@@ -73,8 +81,9 @@ func RemoteAddrHandler(fieldKey string) func(next http.Handler) http.Handler {
 		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 			if host, _, err := net.SplitHostPort(r.RemoteAddr); err == nil {
 				log := zerolog.Ctx(r.Context())
-				log = log.With().Str(fieldKey, host).Logger()
-				r = r.WithContext(log.WithContext(r.Context()))
+				log.UpdateContext(func(c zerolog.Context) zerolog.Context {
+					return c.Str(fieldKey, host)
+				})
 			}
 			next.ServeHTTP(w, r)
 		})
@@ -88,8 +97,9 @@ func UserAgentHandler(fieldKey string) func(next http.Handler) http.Handler {
 		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 			if ua := r.Header.Get("User-Agent"); ua != "" {
 				log := zerolog.Ctx(r.Context())
-				log = log.With().Str(fieldKey, ua).Logger()
-				r = r.WithContext(log.WithContext(r.Context()))
+				log.UpdateContext(func(c zerolog.Context) zerolog.Context {
+					return c.Str(fieldKey, ua)
+				})
 			}
 			next.ServeHTTP(w, r)
 		})
@@ -103,8 +113,9 @@ func RefererHandler(fieldKey string) func(next http.Handler) http.Handler {
 		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 			if ref := r.Header.Get("Referer"); ref != "" {
 				log := zerolog.Ctx(r.Context())
-				log = log.With().Str(fieldKey, ref).Logger()
-				r = r.WithContext(log.WithContext(r.Context()))
+				log.UpdateContext(func(c zerolog.Context) zerolog.Context {
+					return c.Str(fieldKey, ref)
+				})
 			}
 			next.ServeHTTP(w, r)
 		})
@@ -134,16 +145,18 @@ func IDFromRequest(r *http.Request) (id xid.ID, ok bool) {
 func RequestIDHandler(fieldKey, headerName string) func(next http.Handler) http.Handler {
 	return func(next http.Handler) http.Handler {
 		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			ctx := r.Context()
 			id, ok := IDFromRequest(r)
 			if !ok {
 				id = xid.New()
-				ctx := context.WithValue(r.Context(), idKey{}, id)
+				ctx = context.WithValue(ctx, idKey{}, id)
 				r = r.WithContext(ctx)
 			}
 			if fieldKey != "" {
-				log := zerolog.Ctx(r.Context())
-				log = log.With().Str(fieldKey, id.String()).Logger()
-				r = r.WithContext(log.WithContext(r.Context()))
+				log := zerolog.Ctx(ctx)
+				log.UpdateContext(func(c zerolog.Context) zerolog.Context {
+					return c.Str(fieldKey, id.String())
+				})
 			}
 			if headerName != "" {
 				w.Header().Set(headerName, id.String())
@@ -152,3 +165,15 @@ func RequestIDHandler(fieldKey, headerName string) func(next http.Handler) http.
 		})
 	}
 }
+
+// AccessHandler returns a handler that call f after each request.
+func AccessHandler(f func(r *http.Request, status, size int, duration time.Duration)) func(next http.Handler) http.Handler {
+	return func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			start := time.Now()
+			lw := mutil.WrapWriter(w)
+			next.ServeHTTP(lw, r)
+			f(r, lw.Status(), lw.BytesWritten(), time.Since(start))
+		})
+	}
+}

hlog/hlog_test.go

@@ -5,6 +5,7 @@ package hlog
 import (
 	"bytes"
 	"fmt"
+	"io/ioutil"
 	"net/http"
 	"net/url"
 	"testing"
@@ -23,7 +24,7 @@ func TestNewHandler(t *testing.T) {
 	lh := NewHandler(log)
 	h := lh(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		l := FromRequest(r)
-		if !reflect.DeepEqual(l, log) {
+		if !reflect.DeepEqual(*l, log) {
 			t.Fail()
 		}
 	}))
@@ -38,12 +39,12 @@ func TestURLHandler(t *testing.T) {
 	h := URLHandler("url")(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		l := FromRequest(r)
 		l.Log().Msg("")
-		if want, got := `{"url":"/path?foo=bar"}`+"\n", out.String(); want != got {
-			t.Errorf("Invalid log output, got: %s, want: %s", got, want)
-		}
 	}))
 	h = NewHandler(zerolog.New(out))(h)
 	h.ServeHTTP(nil, r)
+	if want, got := `{"url":"/path?foo=bar"}`+"\n", out.String(); want != got {
+		t.Errorf("Invalid log output, got: %s, want: %s", got, want)
+	}
 }
 
 func TestMethodHandler(t *testing.T) {
@@ -54,12 +55,12 @@ func TestMethodHandler(t *testing.T) {
 	h := MethodHandler("method")(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		l := FromRequest(r)
 		l.Log().Msg("")
-		if want, got := `{"method":"POST"}`+"\n", out.String(); want != got {
-			t.Errorf("Invalid log output, got: %s, want: %s", got, want)
-		}
 	}))
 	h = NewHandler(zerolog.New(out))(h)
 	h.ServeHTTP(nil, r)
+	if want, got := `{"method":"POST"}`+"\n", out.String(); want != got {
+		t.Errorf("Invalid log output, got: %s, want: %s", got, want)
+	}
 }
 
 func TestRequestHandler(t *testing.T) {
@@ -71,12 +72,12 @@ func TestRequestHandler(t *testing.T) {
 	h := RequestHandler("request")(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		l := FromRequest(r)
 		l.Log().Msg("")
-		if want, got := `{"request":"POST /path?foo=bar"}`+"\n", out.String(); want != got {
-			t.Errorf("Invalid log output, got: %s, want: %s", got, want)
-		}
 	}))
 	h = NewHandler(zerolog.New(out))(h)
 	h.ServeHTTP(nil, r)
+	if want, got := `{"request":"POST /path?foo=bar"}`+"\n", out.String(); want != got {
+		t.Errorf("Invalid log output, got: %s, want: %s", got, want)
+	}
 }
 
 func TestRemoteAddrHandler(t *testing.T) {
@@ -87,12 +88,12 @@ func TestRemoteAddrHandler(t *testing.T) {
 	h := RemoteAddrHandler("ip")(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		l := FromRequest(r)
 		l.Log().Msg("")
-		if want, got := `{"ip":"1.2.3.4"}`+"\n", out.String(); want != got {
-			t.Errorf("Invalid log output, got: %s, want: %s", got, want)
-		}
 	}))
 	h = NewHandler(zerolog.New(out))(h)
 	h.ServeHTTP(nil, r)
+	if want, got := `{"ip":"1.2.3.4"}`+"\n", out.String(); want != got {
+		t.Errorf("Invalid log output, got: %s, want: %s", got, want)
+	}
 }
 
 func TestRemoteAddrHandlerIPv6(t *testing.T) {
@@ -103,12 +104,12 @@ func TestRemoteAddrHandlerIPv6(t *testing.T) {
 	h := RemoteAddrHandler("ip")(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		l := FromRequest(r)
 		l.Log().Msg("")
-		if want, got := `{"ip":"2001:db8:a0b:12f0::1"}`+"\n", out.String(); want != got {
-			t.Errorf("Invalid log output, got: %s, want: %s", got, want)
-		}
 	}))
 	h = NewHandler(zerolog.New(out))(h)
 	h.ServeHTTP(nil, r)
+	if want, got := `{"ip":"2001:db8:a0b:12f0::1"}`+"\n", out.String(); want != got {
+		t.Errorf("Invalid log output, got: %s, want: %s", got, want)
+	}
 }
 
 func TestUserAgentHandler(t *testing.T) {
@@ -121,12 +122,12 @@ func TestUserAgentHandler(t *testing.T) {
 	h := UserAgentHandler("ua")(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		l := FromRequest(r)
 		l.Log().Msg("")
-		if want, got := `{"ua":"some user agent string"}`+"\n", out.String(); want != got {
-			t.Errorf("Invalid log output, got: %s, want: %s", got, want)
-		}
 	}))
 	h = NewHandler(zerolog.New(out))(h)
 	h.ServeHTTP(nil, r)
+	if want, got := `{"ua":"some user agent string"}`+"\n", out.String(); want != got {
+		t.Errorf("Invalid log output, got: %s, want: %s", got, want)
+	}
 }
 
 func TestRefererHandler(t *testing.T) {
@@ -139,12 +140,12 @@ func TestRefererHandler(t *testing.T) {
 	h := RefererHandler("referer")(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		l := FromRequest(r)
 		l.Log().Msg("")
-		if want, got := `{"referer":"http://foo.com/bar"}`+"\n", out.String(); want != got {
-			t.Errorf("Invalid log output, got: %s, want: %s", got, want)
-		}
 	}))
 	h = NewHandler(zerolog.New(out))(h)
 	h.ServeHTTP(nil, r)
+	if want, got := `{"referer":"http://foo.com/bar"}`+"\n", out.String(); want != got {
+		t.Errorf("Invalid log output, got: %s, want: %s", got, want)
+	}
 }
 
 func TestRequestIDHandler(t *testing.T) {
@@ -171,3 +172,66 @@ func TestRequestIDHandler(t *testing.T) {
 	h = NewHandler(zerolog.New(out))(h)
 	h.ServeHTTP(httptest.NewRecorder(), r)
 }
+
+func TestCombinedHandlers(t *testing.T) {
+	out := &bytes.Buffer{}
+	r := &http.Request{
+		Method: "POST",
+		URL:    &url.URL{Path: "/path", RawQuery: "foo=bar"},
+	}
+	h := MethodHandler("method")(RequestHandler("request")(URLHandler("url")(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		l := FromRequest(r)
+		l.Log().Msg("")
+	}))))
+	h = NewHandler(zerolog.New(out))(h)
+	h.ServeHTTP(nil, r)
+	if want, got := `{"method":"POST","request":"POST /path?foo=bar","url":"/path?foo=bar"}`+"\n", out.String(); want != got {
+		t.Errorf("Invalid log output, got: %s, want: %s", got, want)
+	}
+}
+
+func BenchmarkHandlers(b *testing.B) {
+	r := &http.Request{
+		Method: "POST",
+		URL:    &url.URL{Path: "/path", RawQuery: "foo=bar"},
+	}
+	h1 := URLHandler("url")(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		l := FromRequest(r)
+		l.Log().Msg("")
+	}))
+	h2 := MethodHandler("method")(RequestHandler("request")(h1))
+	handlers := map[string]http.Handler{
+		"Single":           NewHandler(zerolog.New(ioutil.Discard))(h1),
+		"Combined":         NewHandler(zerolog.New(ioutil.Discard))(h2),
+		"SingleDisabled":   NewHandler(zerolog.New(ioutil.Discard).Level(zerolog.Disabled))(h1),
+		"CombinedDisabled": NewHandler(zerolog.New(ioutil.Discard).Level(zerolog.Disabled))(h2),
+	}
+	for name := range handlers {
+		h := handlers[name]
+		b.Run(name, func(b *testing.B) {
+			for i := 0; i < b.N; i++ {
+				h.ServeHTTP(nil, r)
+			}
+		})
+	}
+}
+
+func BenchmarkDataRace(b *testing.B) {
+	log := zerolog.New(nil).With().
+		Str("foo", "bar").
+		Logger()
+	lh := NewHandler(log)
+	h := lh(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		l := FromRequest(r)
+		l.UpdateContext(func(c zerolog.Context) zerolog.Context {
+			return c.Str("bar", "baz")
+		})
+		l.Log().Msg("")
+	}))
+
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			h.ServeHTTP(nil, &http.Request{})
+		}
+	})
+}

hook.go

@@ -0,0 +1,51 @@
+package zerolog
+
+// Hook defines an interface to a log hook.
+type Hook interface {
+	// Run runs the hook with the event.
+	Run(e *Event, level Level, message string)
+}
+
+// LevelHook applies a different hook for each level.
+type LevelHook struct {
+	NoLevelHook, DebugHook, InfoHook, WarnHook, ErrorHook, FatalHook, PanicHook Hook
+}
+
+// Run implements the Hook interface.
+func (h LevelHook) Run(e *Event, level Level, message string) {
+	switch level {
+	case DebugLevel:
+		if h.DebugHook != nil {
+			h.DebugHook.Run(e, level, message)
+		}
+	case InfoLevel:
+		if h.InfoHook != nil {
+			h.InfoHook.Run(e, level, message)
+		}
+	case WarnLevel:
+		if h.WarnHook != nil {
+			h.WarnHook.Run(e, level, message)
+		}
+	case ErrorLevel:
+		if h.ErrorHook != nil {
+			h.ErrorHook.Run(e, level, message)
+		}
+	case FatalLevel:
+		if h.FatalHook != nil {
+			h.FatalHook.Run(e, level, message)
+		}
+	case PanicLevel:
+		if h.PanicHook != nil {
+			h.PanicHook.Run(e, level, message)
+		}
+	case NoLevel:
+		if h.NoLevelHook != nil {
+			h.NoLevelHook.Run(e, level, message)
+		}
+	}
+}
+
+// NewLevelHook returns a new LevelHook.
+func NewLevelHook() LevelHook {
+	return LevelHook{}
+}

hook_test.go

@@ -0,0 +1,236 @@
+package zerolog
+
+import (
+	"testing"
+	"bytes"
+	"io/ioutil"
+)
+
+type LevelNameHook struct{}
+
+func (h LevelNameHook) Run(e *Event, level Level, msg string) {
+	levelName := level.String()
+	if level == NoLevel {
+		levelName = "nolevel"
+	}
+	e.Str("level_name", levelName)
+}
+
+type SimpleHook struct{}
+
+func (h SimpleHook) Run(e *Event, level Level, msg string) {
+	e.Bool("has_level", level != NoLevel)
+	e.Str("test", "logged")
+}
+
+type CopyHook struct{}
+
+func (h CopyHook) Run(e *Event, level Level, msg string) {
+	hasLevel := level != NoLevel
+	e.Bool("copy_has_level", hasLevel)
+	if hasLevel {
+		e.Str("copy_level", level.String())
+	}
+	e.Str("copy_msg", msg)
+}
+
+type NopHook struct{}
+
+func (h NopHook) Run(e *Event, level Level, msg string) {
+}
+
+var (
+	levelNameHook LevelNameHook
+	simpleHook    SimpleHook
+	copyHook      CopyHook
+	nopHook       NopHook
+)
+
+func TestHook(t *testing.T) {
+	t.Run("Message", func(t *testing.T) {
+		out := &bytes.Buffer{}
+		log := New(out).Hook(levelNameHook)
+		log.Log().Msg("test message")
+		if got, want := out.String(), `{"level_name":"nolevel","message":"test message"}`+"\n"; got != want {
+			t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
+		}
+	})
+	t.Run("NoLevel", func(t *testing.T) {
+		out := &bytes.Buffer{}
+		log := New(out).Hook(levelNameHook)
+		log.Log().Msg("")
+		if got, want := out.String(), `{"level_name":"nolevel"}`+"\n"; got != want {
+			t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
+		}
+	})
+	t.Run("Print", func(t *testing.T) {
+		out := &bytes.Buffer{}
+		log := New(out).Hook(levelNameHook)
+		log.Print("")
+		if got, want := out.String(), `{"level":"debug","level_name":"debug"}`+"\n"; got != want {
+			t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
+		}
+	})
+	t.Run("Error", func(t *testing.T) {
+		out := &bytes.Buffer{}
+		log := New(out).Hook(levelNameHook)
+		log.Error().Msg("")
+		if got, want := out.String(), `{"level":"error","level_name":"error"}`+"\n"; got != want {
+			t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
+		}
+	})
+	t.Run("Copy/1", func(t *testing.T) {
+		out := &bytes.Buffer{}
+		log := New(out).Hook(copyHook)
+		log.Log().Msg("")
+		if got, want := out.String(), `{"copy_has_level":false,"copy_msg":""}`+"\n"; got != want {
+			t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
+		}
+	})
+	t.Run("Copy/2", func(t *testing.T) {
+		out := &bytes.Buffer{}
+		log := New(out).Hook(copyHook)
+		log.Info().Msg("a message")
+		if got, want := out.String(), `{"level":"info","copy_has_level":true,"copy_level":"info","copy_msg":"a message","message":"a message"}`+"\n"; got != want {
+			t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
+		}
+	})
+	t.Run("Multi", func(t *testing.T) {
+		out := &bytes.Buffer{}
+		log := New(out).Hook(levelNameHook).Hook(simpleHook)
+		log.Error().Msg("")
+		if got, want := out.String(), `{"level":"error","level_name":"error","has_level":true,"test":"logged"}`+"\n"; got != want {
+			t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
+		}
+	})
+	t.Run("Multi/Message", func(t *testing.T) {
+		out := &bytes.Buffer{}
+		log := New(out).Hook(levelNameHook).Hook(simpleHook)
+		log.Error().Msg("a message")
+		if got, want := out.String(), `{"level":"error","level_name":"error","has_level":true,"test":"logged","message":"a message"}`+"\n"; got != want {
+			t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
+		}
+	})
+	t.Run("Output/single/pre", func(t *testing.T) {
+		ignored := &bytes.Buffer{}
+		out := &bytes.Buffer{}
+		log := New(ignored).Hook(levelNameHook).Output(out)
+		log.Error().Msg("")
+		if got, want := out.String(), `{"level":"error","level_name":"error"}`+"\n"; got != want {
+			t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
+		}
+	})
+	t.Run("Output/single/post", func(t *testing.T) {
+		ignored := &bytes.Buffer{}
+		out := &bytes.Buffer{}
+		log := New(ignored).Output(out).Hook(levelNameHook)
+		log.Error().Msg("")
+		if got, want := out.String(), `{"level":"error","level_name":"error"}`+"\n"; got != want {
+			t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
+		}
+	})
+	t.Run("Output/multi/pre", func(t *testing.T) {
+		ignored := &bytes.Buffer{}
+		out := &bytes.Buffer{}
+		log := New(ignored).Hook(levelNameHook).Hook(simpleHook).Output(out)
+		log.Error().Msg("")
+		if got, want := out.String(), `{"level":"error","level_name":"error","has_level":true,"test":"logged"}`+"\n"; got != want {
+			t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
+		}
+	})
+	t.Run("Output/multi/post", func(t *testing.T) {
+		ignored := &bytes.Buffer{}
+		out := &bytes.Buffer{}
+		log := New(ignored).Output(out).Hook(levelNameHook).Hook(simpleHook)
+		log.Error().Msg("")
+		if got, want := out.String(), `{"level":"error","level_name":"error","has_level":true,"test":"logged"}`+"\n"; got != want {
+			t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
+		}
+	})
+	t.Run("Output/mixed", func(t *testing.T) {
+		ignored := &bytes.Buffer{}
+		out := &bytes.Buffer{}
+		log := New(ignored).Hook(levelNameHook).Output(out).Hook(simpleHook)
+		log.Error().Msg("")
+		if got, want := out.String(), `{"level":"error","level_name":"error","has_level":true,"test":"logged"}`+"\n"; got != want {
+			t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
+		}
+	})
+	t.Run("With/single/pre", func(t *testing.T) {
+		out := &bytes.Buffer{}
+		log := New(out).Hook(levelNameHook).With().Str("with", "pre").Logger()
+		log.Error().Msg("")
+		if got, want := out.String(), `{"level":"error","with":"pre","level_name":"error"}`+"\n"; got != want {
+			t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
+		}
+	})
+	t.Run("With/single/post", func(t *testing.T) {
+		out := &bytes.Buffer{}
+		log := New(out).With().Str("with", "post").Logger().Hook(levelNameHook)
+		log.Error().Msg("")
+		if got, want := out.String(), `{"level":"error","with":"post","level_name":"error"}`+"\n"; got != want {
+			t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
+		}
+	})
+	t.Run("With/multi/pre", func(t *testing.T) {
+		out := &bytes.Buffer{}
+		log := New(out).Hook(levelNameHook).Hook(simpleHook).With().Str("with", "pre").Logger()
+		log.Error().Msg("")
+		if got, want := out.String(), `{"level":"error","with":"pre","level_name":"error","has_level":true,"test":"logged"}`+"\n"; got != want {
+			t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
+		}
+	})
+	t.Run("With/multi/post", func(t *testing.T) {
+		out := &bytes.Buffer{}
+		log := New(out).With().Str("with", "post").Logger().Hook(levelNameHook).Hook(simpleHook)
+		log.Error().Msg("")
+		if got, want := out.String(), `{"level":"error","with":"post","level_name":"error","has_level":true,"test":"logged"}`+"\n"; got != want {
+			t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
+		}
+	})
+	t.Run("With/mixed", func(t *testing.T) {
+		out := &bytes.Buffer{}
+		log := New(out).Hook(levelNameHook).With().Str("with", "mixed").Logger().Hook(simpleHook)
+		log.Error().Msg("")
+		if got, want := out.String(), `{"level":"error","with":"mixed","level_name":"error","has_level":true,"test":"logged"}`+"\n"; got != want {
+			t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
+		}
+	})
+	t.Run("None", func(t *testing.T) {
+		out := &bytes.Buffer{}
+		log := New(out)
+		log.Error().Msg("")
+		if got, want := out.String(), `{"level":"error"}`+"\n"; got != want {
+			t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
+		}
+	})
+}
+
+func BenchmarkHooks(b *testing.B) {
+	logger := New(ioutil.Discard)
+	b.ResetTimer()
+	b.Run("Nop/Single", func(b *testing.B) {
+		log := logger.Hook(nopHook)
+		b.RunParallel(func(pb *testing.PB) {
+			for pb.Next() {
+				log.Log().Msg("")
+			}
+		})
+	})
+	b.Run("Nop/Multi", func(b *testing.B) {
+		log := logger.Hook(nopHook).Hook(nopHook)
+		b.RunParallel(func(pb *testing.PB) {
+			for pb.Next() {
+				log.Log().Msg("")
+			}
+		})
+	})
+	b.Run("Simple", func(b *testing.B) {
+		log := logger.Hook(simpleHook)
+		b.RunParallel(func(pb *testing.PB) {
+			for pb.Next() {
+				log.Log().Msg("")
+			}
+		})
+	})
+}

internal/json/base.go

@@ -0,0 +1,39 @@
+package json
+
+func AppendKey(dst []byte, key string) []byte {
+	if len(dst) > 1 {
+		dst = append(dst, ',')
+	}
+	dst = AppendString(dst, key)
+	return append(dst, ':')
+}
+
+func AppendError(dst []byte, err error) []byte {
+	if err == nil {
+		return append(dst, `null`...)
+	}
+	return AppendString(dst, err.Error())
+}
+
+func AppendErrors(dst []byte, errs []error) []byte {
+	if len(errs) == 0 {
+		return append(dst, '[', ']')
+	}
+	dst = append(dst, '[')
+	if errs[0] != nil {
+		dst = AppendString(dst, errs[0].Error())
+	} else {
+		dst = append(dst, "null"...)
+	}
+	if len(errs) > 1 {
+		for _, err := range errs[1:] {
+			if err == nil {
+				dst = append(dst, ",null"...)
+				continue
+			}
+			dst = AppendString(append(dst, ','), err.Error())
+		}
+	}
+	dst = append(dst, ']')
+	return dst
+}

internal/json/string.go

@@ -1,10 +1,25 @@
-package zerolog
+package json
 
 import "unicode/utf8"
 
 const hex = "0123456789abcdef"
 
-// appendJSONString encodes the input string to json and appends
+func AppendStrings(dst []byte, vals []string) []byte {
+	if len(vals) == 0 {
+		return append(dst, '[', ']')
+	}
+	dst = append(dst, '[')
+	dst = AppendString(dst, vals[0])
+	if len(vals) > 1 {
+		for _, val := range vals[1:] {
+			dst = AppendString(append(dst, ','), val)
+		}
+	}
+	dst = append(dst, ']')
+	return dst
+}
+
+// AppendString encodes the input string to json and appends
 // the encoded string to the input byte slice.
 //
 // The operation loops though each byte in the string looking
@@ -13,7 +28,7 @@ const hex = "0123456789abcdef"
 // entirety to the byte slice.
 // If we encounter a byte that does need encoding, switch up
 // the operation and perform a byte-by-byte read-encode-append.
-func appendJSONString(dst []byte, s string) []byte {
+func AppendString(dst []byte, s string) []byte {
 	// Start with a double quote.
 	dst = append(dst, '"')
 	// Loop through each character in the string.
@@ -24,7 +39,7 @@ func appendJSONString(dst []byte, s string) []byte {
 		if s[i] < 0x20 || s[i] > 0x7e || s[i] == '\\' || s[i] == '"' {
 			// We encountered a character that needs to be encoded. Switch
 			// to complex version of the algorithm.
-			dst = appendJSONStringComplex(dst, s, i)
+			dst = appendStringComplex(dst, s, i)
 			return append(dst, '"')
 		}
 	}
@@ -35,10 +50,10 @@ func appendJSONString(dst []byte, s string) []byte {
 	return append(dst, '"')
 }
 
-// appendJSONStringComplex is used by appendJSONString to take over an in
+// appendStringComplex is used by appendString to take over an in
 // progress JSON string encoding that encountered a character that needs
 // to be encoded.
-func appendJSONStringComplex(dst []byte, s string, i int) []byte {
+func appendStringComplex(dst []byte, s string, i int) []byte {
 	start := 0
 	for i < len(s) {
 		b := s[i]
@@ -94,3 +109,72 @@ func appendJSONStringComplex(dst []byte, s string, i int) []byte {
 	}
 	return dst
 }
+
+// AppendBytes is a mirror of appendString with []byte arg
+func AppendBytes(dst, s []byte) []byte {
+	dst = append(dst, '"')
+	for i := 0; i < len(s); i++ {
+		if s[i] < 0x20 || s[i] > 0x7e || s[i] == '\\' || s[i] == '"' {
+			dst = appendBytesComplex(dst, s, i)
+			return append(dst, '"')
+		}
+	}
+	dst = append(dst, s...)
+	return append(dst, '"')
+}
+
+// appendBytesComplex is a mirror of the appendStringComplex
+// with []byte arg
+func appendBytesComplex(dst, s []byte, i int) []byte {
+	start := 0
+	for i < len(s) {
+		b := s[i]
+		if b >= utf8.RuneSelf {
+			r, size := utf8.DecodeRune(s[i:])
+			if r == utf8.RuneError && size == 1 {
+				if start < i {
+					dst = append(dst, s[start:i]...)
+				}
+				dst = append(dst, `\ufffd`...)
+				i += size
+				start = i
+				continue
+			}
+			i += size
+			continue
+		}
+		if b >= 0x20 && b <= 0x7e && b != '\\' && b != '"' {
+			i++
+			continue
+		}
+		// We encountered a character that needs to be encoded.
+		// Let's append the previous simple characters to the byte slice
+		// and switch our operation to read and encode the remainder
+		// characters byte-by-byte.
+		if start < i {
+			dst = append(dst, s[start:i]...)
+		}
+		switch b {
+		case '"', '\\':
+			dst = append(dst, '\\', b)
+		case '\b':
+			dst = append(dst, '\\', 'b')
+		case '\f':
+			dst = append(dst, '\\', 'f')
+		case '\n':
+			dst = append(dst, '\\', 'n')
+		case '\r':
+			dst = append(dst, '\\', 'r')
+		case '\t':
+			dst = append(dst, '\\', 't')
+		default:
+			dst = append(dst, '\\', 'u', '0', '0', hex[b>>4], hex[b&0xF])
+		}
+		i++
+		start = i
+	}
+	if start < len(s) {
+		dst = append(dst, s[start:]...)
+	}
+	return dst
+}

internal/json/string_test.go

@@ -0,0 +1,150 @@
+package json
+
+import (
+	"testing"
+	"unicode"
+)
+
+var encodeStringTests = []struct {
+	in  string
+	out string
+}{
+	{"", `""`},
+	{"\\", `"\\"`},
+	{"\x00", `"\u0000"`},
+	{"\x01", `"\u0001"`},
+	{"\x02", `"\u0002"`},
+	{"\x03", `"\u0003"`},
+	{"\x04", `"\u0004"`},
+	{"\x05", `"\u0005"`},
+	{"\x06", `"\u0006"`},
+	{"\x07", `"\u0007"`},
+	{"\x08", `"\b"`},
+	{"\x09", `"\t"`},
+	{"\x0a", `"\n"`},
+	{"\x0b", `"\u000b"`},
+	{"\x0c", `"\f"`},
+	{"\x0d", `"\r"`},
+	{"\x0e", `"\u000e"`},
+	{"\x0f", `"\u000f"`},
+	{"\x10", `"\u0010"`},
+	{"\x11", `"\u0011"`},
+	{"\x12", `"\u0012"`},
+	{"\x13", `"\u0013"`},
+	{"\x14", `"\u0014"`},
+	{"\x15", `"\u0015"`},
+	{"\x16", `"\u0016"`},
+	{"\x17", `"\u0017"`},
+	{"\x18", `"\u0018"`},
+	{"\x19", `"\u0019"`},
+	{"\x1a", `"\u001a"`},
+	{"\x1b", `"\u001b"`},
+	{"\x1c", `"\u001c"`},
+	{"\x1d", `"\u001d"`},
+	{"\x1e", `"\u001e"`},
+	{"\x1f", `"\u001f"`},
+	{"✭", `"✭"`},
+	{"foo\xc2\x7fbar", `"foo\ufffd\u007fbar"`}, // invalid sequence
+	{"ascii", `"ascii"`},
+	{"\"a", `"\"a"`},
+	{"\x1fa", `"\u001fa"`},
+	{"foo\"bar\"baz", `"foo\"bar\"baz"`},
+	{"\x1ffoo\x1fbar\x1fbaz", `"\u001ffoo\u001fbar\u001fbaz"`},
+	{"emoji \u2764\ufe0f!", `"emoji ❤️!"`},
+}
+
+func TestappendString(t *testing.T) {
+	for _, tt := range encodeStringTests {
+		b := AppendString([]byte{}, tt.in)
+		if got, want := string(b), tt.out; got != want {
+			t.Errorf("appendString(%q) = %#q, want %#q", tt.in, got, want)
+		}
+	}
+}
+
+func TestappendBytes(t *testing.T) {
+	for _, tt := range encodeStringTests {
+		b := AppendBytes([]byte{}, []byte(tt.in))
+		if got, want := string(b), tt.out; got != want {
+			t.Errorf("appendBytes(%q) = %#q, want %#q", tt.in, got, want)
+		}
+	}
+}
+
+func TestStringBytes(t *testing.T) {
+	t.Parallel()
+	// Test that encodeState.stringBytes and encodeState.string use the same encoding.
+	var r []rune
+	for i := '\u0000'; i <= unicode.MaxRune; i++ {
+		r = append(r, i)
+	}
+	s := string(r) + "\xff\xff\xffhello" // some invalid UTF-8 too
+
+	enc := string(AppendString([]byte{}, s))
+	encBytes := string(AppendBytes([]byte{}, []byte(s)))
+
+	if enc != encBytes {
+		i := 0
+		for i < len(enc) && i < len(encBytes) && enc[i] == encBytes[i] {
+			i++
+		}
+		enc = enc[i:]
+		encBytes = encBytes[i:]
+		i = 0
+		for i < len(enc) && i < len(encBytes) && enc[len(enc)-i-1] == encBytes[len(encBytes)-i-1] {
+			i++
+		}
+		enc = enc[:len(enc)-i]
+		encBytes = encBytes[:len(encBytes)-i]
+
+		if len(enc) > 20 {
+			enc = enc[:20] + "..."
+		}
+		if len(encBytes) > 20 {
+			encBytes = encBytes[:20] + "..."
+		}
+
+		t.Errorf("encodings differ at %#q vs %#q", enc, encBytes)
+	}
+}
+
+func BenchmarkappendString(b *testing.B) {
+	tests := map[string]string{
+		"NoEncoding":       `aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa`,
+		"EncodingFirst":    `"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa`,
+		"EncodingMiddle":   `aaaaaaaaaaaaaaaaaaaaaaaaa"aaaaaaaaaaaaaaaaaaaaaaaa`,
+		"EncodingLast":     `aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"`,
+		"MultiBytesFirst":  `❤️aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa`,
+		"MultiBytesMiddle": `aaaaaaaaaaaaaaaaaaaaaaaaa❤️aaaaaaaaaaaaaaaaaaaaaaaa`,
+		"MultiBytesLast":   `aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa❤️`,
+	}
+	for name, str := range tests {
+		b.Run(name, func(b *testing.B) {
+			buf := make([]byte, 0, 100)
+			for i := 0; i < b.N; i++ {
+				_ = AppendString(buf, str)
+			}
+		})
+	}
+}
+
+func BenchmarkappendBytes(b *testing.B) {
+	tests := map[string]string{
+		"NoEncoding":       `aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa`,
+		"EncodingFirst":    `"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa`,
+		"EncodingMiddle":   `aaaaaaaaaaaaaaaaaaaaaaaaa"aaaaaaaaaaaaaaaaaaaaaaaa`,
+		"EncodingLast":     `aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"`,
+		"MultiBytesFirst":  `❤️aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa`,
+		"MultiBytesMiddle": `aaaaaaaaaaaaaaaaaaaaaaaaa❤️aaaaaaaaaaaaaaaaaaaaaaaa`,
+		"MultiBytesLast":   `aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa❤️`,
+	}
+	for name, str := range tests {
+		byt := []byte(str)
+		b.Run(name, func(b *testing.B) {
+			buf := make([]byte, 0, 100)
+			for i := 0; i < b.N; i++ {
+				_ = AppendBytes(buf, byt)
+			}
+		})
+	}
+}

internal/json/time.go

@@ -0,0 +1,68 @@
+package json
+
+import (
+	"strconv"
+	"time"
+)
+
+func AppendTime(dst []byte, t time.Time, format string) []byte {
+	if format == "" {
+		return AppendInt64(dst, t.Unix())
+	}
+	return append(t.AppendFormat(append(dst, '"'), format), '"')
+}
+
+func AppendTimes(dst []byte, vals []time.Time, format string) []byte {
+	if format == "" {
+		return appendUnixTimes(dst, vals)
+	}
+	if len(vals) == 0 {
+		return append(dst, '[', ']')
+	}
+	dst = append(dst, '[')
+	dst = append(vals[0].AppendFormat(append(dst, '"'), format), '"')
+	if len(vals) > 1 {
+		for _, t := range vals[1:] {
+			dst = append(t.AppendFormat(append(dst, ',', '"'), format), '"')
+		}
+	}
+	dst = append(dst, ']')
+	return dst
+}
+
+func appendUnixTimes(dst []byte, vals []time.Time) []byte {
+	if len(vals) == 0 {
+		return append(dst, '[', ']')
+	}
+	dst = append(dst, '[')
+	dst = strconv.AppendInt(dst, vals[0].Unix(), 10)
+	if len(vals) > 1 {
+		for _, t := range vals[1:] {
+			dst = strconv.AppendInt(dst, t.Unix(), 10)
+		}
+	}
+	dst = append(dst, ']')
+	return dst
+}
+
+func AppendDuration(dst []byte, d time.Duration, unit time.Duration, useInt bool) []byte {
+	if useInt {
+		return strconv.AppendInt(dst, int64(d/unit), 10)
+	}
+	return AppendFloat64(dst, float64(d)/float64(unit))
+}
+
+func AppendDurations(dst []byte, vals []time.Duration, unit time.Duration, useInt bool) []byte {
+	if len(vals) == 0 {
+		return append(dst, '[', ']')
+	}
+	dst = append(dst, '[')
+	dst = AppendDuration(dst, vals[0], unit, useInt)
+	if len(vals) > 1 {
+		for _, d := range vals[1:] {
+			dst = AppendDuration(append(dst, ','), d, unit, useInt)
+		}
+	}
+	dst = append(dst, ']')
+	return dst
+}

internal/json/types.go

@@ -0,0 +1,278 @@
+package json
+
+import (
+	"encoding/json"
+	"fmt"
+	"math"
+	"strconv"
+)
+
+func AppendBool(dst []byte, val bool) []byte {
+	return strconv.AppendBool(dst, val)
+}
+
+func AppendBools(dst []byte, vals []bool) []byte {
+	if len(vals) == 0 {
+		return append(dst, '[', ']')
+	}
+	dst = append(dst, '[')
+	dst = strconv.AppendBool(dst, vals[0])
+	if len(vals) > 1 {
+		for _, val := range vals[1:] {
+			dst = strconv.AppendBool(append(dst, ','), val)
+		}
+	}
+	dst = append(dst, ']')
+	return dst
+}
+
+func AppendInt(dst []byte, val int) []byte {
+	return strconv.AppendInt(dst, int64(val), 10)
+}
+
+func AppendInts(dst []byte, vals []int) []byte {
+	if len(vals) == 0 {
+		return append(dst, '[', ']')
+	}
+	dst = append(dst, '[')
+	dst = strconv.AppendInt(dst, int64(vals[0]), 10)
+	if len(vals) > 1 {
+		for _, val := range vals[1:] {
+			dst = strconv.AppendInt(append(dst, ','), int64(val), 10)
+		}
+	}
+	dst = append(dst, ']')
+	return dst
+}
+
+func AppendInt8(dst []byte, val int8) []byte {
+	return strconv.AppendInt(dst, int64(val), 10)
+}
+
+func AppendInts8(dst []byte, vals []int8) []byte {
+	if len(vals) == 0 {
+		return append(dst, '[', ']')
+	}
+	dst = append(dst, '[')
+	dst = strconv.AppendInt(dst, int64(vals[0]), 10)
+	if len(vals) > 1 {
+		for _, val := range vals[1:] {
+			dst = strconv.AppendInt(append(dst, ','), int64(val), 10)
+		}
+	}
+	dst = append(dst, ']')
+	return dst
+}
+
+func AppendInt16(dst []byte, val int16) []byte {
+	return strconv.AppendInt(dst, int64(val), 10)
+}
+
+func AppendInts16(dst []byte, vals []int16) []byte {
+	if len(vals) == 0 {
+		return append(dst, '[', ']')
+	}
+	dst = append(dst, '[')
+	dst = strconv.AppendInt(dst, int64(vals[0]), 10)
+	if len(vals) > 1 {
+		for _, val := range vals[1:] {
+			dst = strconv.AppendInt(append(dst, ','), int64(val), 10)
+		}
+	}
+	dst = append(dst, ']')
+	return dst
+}
+
+func AppendInt32(dst []byte, val int32) []byte {
+	return strconv.AppendInt(dst, int64(val), 10)
+}
+
+func AppendInts32(dst []byte, vals []int32) []byte {
+	if len(vals) == 0 {
+		return append(dst, '[', ']')
+	}
+	dst = append(dst, '[')
+	dst = strconv.AppendInt(dst, int64(vals[0]), 10)
+	if len(vals) > 1 {
+		for _, val := range vals[1:] {
+			dst = strconv.AppendInt(append(dst, ','), int64(val), 10)
+		}
+	}
+	dst = append(dst, ']')
+	return dst
+}
+
+func AppendInt64(dst []byte, val int64) []byte {
+	return strconv.AppendInt(dst, val, 10)
+}
+
+func AppendInts64(dst []byte, vals []int64) []byte {
+	if len(vals) == 0 {
+		return append(dst, '[', ']')
+	}
+	dst = append(dst, '[')
+	dst = strconv.AppendInt(dst, vals[0], 10)
+	if len(vals) > 1 {
+		for _, val := range vals[1:] {
+			dst = strconv.AppendInt(append(dst, ','), val, 10)
+		}
+	}
+	dst = append(dst, ']')
+	return dst
+}
+
+func AppendUint(dst []byte, val uint) []byte {
+	return strconv.AppendUint(dst, uint64(val), 10)
+}
+
+func AppendUints(dst []byte, vals []uint) []byte {
+	if len(vals) == 0 {
+		return append(dst, '[', ']')
+	}
+	dst = append(dst, '[')
+	dst = strconv.AppendUint(dst, uint64(vals[0]), 10)
+	if len(vals) > 1 {
+		for _, val := range vals[1:] {
+			dst = strconv.AppendUint(append(dst, ','), uint64(val), 10)
+		}
+	}
+	dst = append(dst, ']')
+	return dst
+}
+
+func AppendUint8(dst []byte, val uint8) []byte {
+	return strconv.AppendUint(dst, uint64(val), 10)
+}
+
+func AppendUints8(dst []byte, vals []uint8) []byte {
+	if len(vals) == 0 {
+		return append(dst, '[', ']')
+	}
+	dst = append(dst, '[')
+	dst = strconv.AppendUint(dst, uint64(vals[0]), 10)
+	if len(vals) > 1 {
+		for _, val := range vals[1:] {
+			dst = strconv.AppendUint(append(dst, ','), uint64(val), 10)
+		}
+	}
+	dst = append(dst, ']')
+	return dst
+}
+
+func AppendUint16(dst []byte, val uint16) []byte {
+	return strconv.AppendUint(dst, uint64(val), 10)
+}
+
+func AppendUints16(dst []byte, vals []uint16) []byte {
+	if len(vals) == 0 {
+		return append(dst, '[', ']')
+	}
+	dst = append(dst, '[')
+	dst = strconv.AppendUint(dst, uint64(vals[0]), 10)
+	if len(vals) > 1 {
+		for _, val := range vals[1:] {
+			dst = strconv.AppendUint(append(dst, ','), uint64(val), 10)
+		}
+	}
+	dst = append(dst, ']')
+	return dst
+}
+
+func AppendUint32(dst []byte, val uint32) []byte {
+	return strconv.AppendUint(dst, uint64(val), 10)
+}
+
+func AppendUints32(dst []byte, vals []uint32) []byte {
+	if len(vals) == 0 {
+		return append(dst, '[', ']')
+	}
+	dst = append(dst, '[')
+	dst = strconv.AppendUint(dst, uint64(vals[0]), 10)
+	if len(vals) > 1 {
+		for _, val := range vals[1:] {
+			dst = strconv.AppendUint(append(dst, ','), uint64(val), 10)
+		}
+	}
+	dst = append(dst, ']')
+	return dst
+}
+
+func AppendUint64(dst []byte, val uint64) []byte {
+	return strconv.AppendUint(dst, uint64(val), 10)
+}
+
+func AppendUints64(dst []byte, vals []uint64) []byte {
+	if len(vals) == 0 {
+		return append(dst, '[', ']')
+	}
+	dst = append(dst, '[')
+	dst = strconv.AppendUint(dst, vals[0], 10)
+	if len(vals) > 1 {
+		for _, val := range vals[1:] {
+			dst = strconv.AppendUint(append(dst, ','), val, 10)
+		}
+	}
+	dst = append(dst, ']')
+	return dst
+}
+
+func AppendFloat(dst []byte, val float64, bitSize int) []byte {
+	// JSON does not permit NaN or Infinity. A typical JSON encoder would fail
+	// with an error, but a logging library wants the data to get thru so we
+	// make a tradeoff and store those types as string.
+	switch {
+	case math.IsNaN(val):
+		return append(dst, `"NaN"`...)
+	case math.IsInf(val, 1):
+		return append(dst, `"+Inf"`...)
+	case math.IsInf(val, -1):
+		return append(dst, `"-Inf"`...)
+	}
+	return strconv.AppendFloat(dst, val, 'f', -1, bitSize)
+}
+
+func AppendFloat32(dst []byte, val float32) []byte {
+	return AppendFloat(dst, float64(val), 32)
+}
+
+func AppendFloats32(dst []byte, vals []float32) []byte {
+	if len(vals) == 0 {
+		return append(dst, '[', ']')
+	}
+	dst = append(dst, '[')
+	dst = AppendFloat(dst, float64(vals[0]), 32)
+	if len(vals) > 1 {
+		for _, val := range vals[1:] {
+			dst = AppendFloat(append(dst, ','), float64(val), 32)
+		}
+	}
+	dst = append(dst, ']')
+	return dst
+}
+
+func AppendFloat64(dst []byte, val float64) []byte {
+	return AppendFloat(dst, val, 64)
+}
+
+func AppendFloats64(dst []byte, vals []float64) []byte {
+	if len(vals) == 0 {
+		return append(dst, '[', ']')
+	}
+	dst = append(dst, '[')
+	dst = AppendFloat(dst, vals[0], 32)
+	if len(vals) > 1 {
+		for _, val := range vals[1:] {
+			dst = AppendFloat(append(dst, ','), val, 64)
+		}
+	}
+	dst = append(dst, ']')
+	return dst
+}
+
+func AppendInterface(dst []byte, i interface{}) []byte {
+	marshaled, err := json.Marshal(i)
+	if err != nil {
+		return AppendString(dst, fmt.Sprintf("marshaling error: %v", err))
+	}
+	return append(dst, marshaled...)
+}

internal/json/types_test.go

@@ -0,0 +1,33 @@
+package json
+
+import (
+	"math"
+	"reflect"
+	"testing"
+)
+
+func Test_appendFloat64(t *testing.T) {
+	tests := []struct {
+		name  string
+		input float64
+		want  []byte
+	}{
+		{"-Inf", math.Inf(-1), []byte(`"-Inf"`)},
+		{"+Inf", math.Inf(1), []byte(`"+Inf"`)},
+		{"NaN", math.NaN(), []byte(`"NaN"`)},
+		{"0", 0, []byte(`0`)},
+		{"-1.1", -1.1, []byte(`-1.1`)},
+		{"1e20", 1e20, []byte(`100000000000000000000`)},
+		{"1e21", 1e21, []byte(`1000000000000000000000`)},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := AppendFloat32([]byte{}, float32(tt.input)); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("appendFloat32() = %s, want %s", got, tt.want)
+			}
+			if got := AppendFloat64([]byte{}, tt.input); !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("appendFloat32() = %s, want %s", got, tt.want)
+			}
+		})
+	}
+}

json_test.go

@@ -1,82 +0,0 @@
-package zerolog
-
-import (
-	"testing"
-)
-
-func TestAppendJSONString(t *testing.T) {
-	encodeStringTests := []struct {
-		in  string
-		out string
-	}{
-		{"", `""`},
-		{"\\", `"\\"`},
-		{"\x00", `"\u0000"`},
-		{"\x01", `"\u0001"`},
-		{"\x02", `"\u0002"`},
-		{"\x03", `"\u0003"`},
-		{"\x04", `"\u0004"`},
-		{"\x05", `"\u0005"`},
-		{"\x06", `"\u0006"`},
-		{"\x07", `"\u0007"`},
-		{"\x08", `"\b"`},
-		{"\x09", `"\t"`},
-		{"\x0a", `"\n"`},
-		{"\x0b", `"\u000b"`},
-		{"\x0c", `"\f"`},
-		{"\x0d", `"\r"`},
-		{"\x0e", `"\u000e"`},
-		{"\x0f", `"\u000f"`},
-		{"\x10", `"\u0010"`},
-		{"\x11", `"\u0011"`},
-		{"\x12", `"\u0012"`},
-		{"\x13", `"\u0013"`},
-		{"\x14", `"\u0014"`},
-		{"\x15", `"\u0015"`},
-		{"\x16", `"\u0016"`},
-		{"\x17", `"\u0017"`},
-		{"\x18", `"\u0018"`},
-		{"\x19", `"\u0019"`},
-		{"\x1a", `"\u001a"`},
-		{"\x1b", `"\u001b"`},
-		{"\x1c", `"\u001c"`},
-		{"\x1d", `"\u001d"`},
-		{"\x1e", `"\u001e"`},
-		{"\x1f", `"\u001f"`},
-		{"✭", `"✭"`},
-		{"foo\xc2\x7fbar", `"foo\ufffd\u007fbar"`}, // invalid sequence
-		{"ascii", `"ascii"`},
-		{"\"a", `"\"a"`},
-		{"\x1fa", `"\u001fa"`},
-		{"foo\"bar\"baz", `"foo\"bar\"baz"`},
-		{"\x1ffoo\x1fbar\x1fbaz", `"\u001ffoo\u001fbar\u001fbaz"`},
-		{"emoji \u2764\ufe0f!", `"emoji ❤️!"`},
-	}
-
-	for _, tt := range encodeStringTests {
-		b := appendJSONString([]byte{}, tt.in)
-		if got, want := string(b), tt.out; got != want {
-			t.Errorf("appendJSONString(%q) = %#q, want %#q", tt.in, got, want)
-		}
-	}
-}
-
-func BenchmarkAppendJSONString(b *testing.B) {
-	tests := map[string]string{
-		"NoEncoding":       `aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa`,
-		"EncodingFirst":    `"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa`,
-		"EncodingMiddle":   `aaaaaaaaaaaaaaaaaaaaaaaaa"aaaaaaaaaaaaaaaaaaaaaaaa`,
-		"EncodingLast":     `aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"`,
-		"MultiBytesFirst":  `❤️aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa`,
-		"MultiBytesMiddle": `aaaaaaaaaaaaaaaaaaaaaaaaa❤️aaaaaaaaaaaaaaaaaaaaaaaa`,
-		"MultiBytesLast":   `aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa❤️`,
-	}
-	for name, str := range tests {
-		b.Run(name, func(b *testing.B) {
-			buf := make([]byte, 0, 100)
-			for i := 0; i < b.N; i++ {
-				_ = appendJSONString(buf, str)
-			}
-		})
-	}
-}

log.go

@@ -62,16 +62,36 @@
 //
 // Sample logs:
 //
-//     sampled := log.Sample(10)
+//     sampled := log.Sample(&zerolog.BasicSampler{N: 10})
 //     sampled.Info().Msg("will be logged every 10 messages")
 //
+// Log with contextual hooks:
+//
+//     // Create the hook:
+//     type SeverityHook struct{}
+//
+//     func (h SeverityHook) Run(e *zerolog.Event, level zerolog.Level, msg string) {
+//          if level != zerolog.NoLevel {
+//              e.Str("severity", level.String())
+//          }
+//     }
+//
+//     // And use it:
+//     var h SeverityHook
+//     log := zerolog.New(os.Stdout).Hook(h)
+//     log.Warn().Msg("")
+//     // Output: {"level":"warn","severity":"warn"}
+//
 package zerolog
 
 import (
+	"fmt"
 	"io"
 	"io/ioutil"
 	"os"
-	"sync/atomic"
+	"strconv"
+
+	"github.com/rs/zerolog/internal/json"
 )
 
 // Level defines log levels.
@@ -90,6 +110,8 @@ const (
 	FatalLevel
 	// PanicLevel defines panic log level.
 	PanicLevel
+	// NoLevel defines an absent log level.
+	NoLevel
 	// Disabled disables the logger.
 	Disabled
 )
@@ -108,21 +130,12 @@ func (l Level) String() string {
 		return "fatal"
 	case PanicLevel:
 		return "panic"
+	case NoLevel:
+		return ""
 	}
 	return ""
 }
 
-const (
-	// Often samples log every 10 events.
-	Often = 10
-	// Sometimes samples log every 100 events.
-	Sometimes = 100
-	// Rarely samples log every 1000 events.
-	Rarely = 1000
-)
-
-var disabledEvent = newEvent(levelWriterAdapter{ioutil.Discard}, 0, false)
-
 // A Logger represents an active logging object that generates lines
 // of JSON output to an io.Writer. Each logging operation makes a single
 // call to the Writer's Write method. There is no guaranty on access
@@ -131,9 +144,9 @@ var disabledEvent = newEvent(levelWriterAdapter{ioutil.Discard}, 0, false)
 type Logger struct {
 	w       LevelWriter
 	level   Level
-	sample  uint32
-	counter *uint32
+	sampler Sampler
 	context []byte
+	hooks   []Hook
 }
 
 // New creates a root logger with given output writer. If the output writer implements
@@ -159,6 +172,21 @@ func Nop() Logger {
 	return New(nil).Level(Disabled)
 }
 
+// Output duplicates the current logger and sets w as its output.
+func (l Logger) Output(w io.Writer) Logger {
+	l2 := New(w)
+	l2.level = l.level
+	l2.sampler = l.sampler
+	if len(l.hooks) > 0 {
+		l2.hooks = append(l2.hooks, l.hooks...)
+	}
+	if l.context != nil {
+		l2.context = make([]byte, len(l.context), cap(l.context))
+		copy(l2.context, l.context)
+	}
+	return l2
+}
+
 // With creates a child logger with the field added to its context.
 func (l Logger) With() Context {
 	context := l.context
@@ -172,88 +200,130 @@ func (l Logger) With() Context {
 	return Context{l}
 }
 
-// Level creates a child logger with the minimum accepted level set to level.
-func (l Logger) Level(lvl Level) Logger {
-	return Logger{
-		w:       l.w,
-		level:   lvl,
-		sample:  l.sample,
-		counter: l.counter,
-		context: l.context,
+// UpdateContext updates the internal logger's context.
+//
+// Use this method with caution. If unsure, prefer the With method.
+func (l *Logger) UpdateContext(update func(c Context) Context) {
+	if l == disabledLogger {
+		return
 	}
+	if cap(l.context) == 0 {
+		l.context = make([]byte, 1, 500) // first byte is timestamp flag
+	}
+	c := update(Context{*l})
+	l.context = c.l.context
 }
 
-// Sample returns a logger that only let one message out of every to pass thru.
-func (l Logger) Sample(every int) Logger {
-	if every == 0 {
-		// Create a child with no sampling.
-		return Logger{
-			w:       l.w,
-			level:   l.level,
-			context: l.context,
-		}
-	}
-	return Logger{
-		w:       l.w,
-		level:   l.level,
-		sample:  uint32(every),
-		counter: new(uint32),
-		context: l.context,
-	}
+// Level creates a child logger with the minimum accepted level set to level.
+func (l Logger) Level(lvl Level) Logger {
+	l.level = lvl
+	return l
+}
+
+// Sample returns a logger with the s sampler.
+func (l Logger) Sample(s Sampler) Logger {
+	l.sampler = s
+	return l
+}
+
+// Hook returns a logger with the h Hook.
+func (l Logger) Hook(h Hook) Logger {
+	l.hooks = append(l.hooks, h)
+	return l
 }
 
 // Debug starts a new message with debug level.
 //
 // You must call Msg on the returned event in order to send the event.
-func (l Logger) Debug() *Event {
-	return l.newEvent(DebugLevel, true, nil)
+func (l *Logger) Debug() *Event {
+	return l.newEvent(DebugLevel, nil)
 }
 
 // Info starts a new message with info level.
 //
 // You must call Msg on the returned event in order to send the event.
-func (l Logger) Info() *Event {
-	return l.newEvent(InfoLevel, true, nil)
+func (l *Logger) Info() *Event {
+	return l.newEvent(InfoLevel, nil)
 }
 
 // Warn starts a new message with warn level.
 //
 // You must call Msg on the returned event in order to send the event.
-func (l Logger) Warn() *Event {
-	return l.newEvent(WarnLevel, true, nil)
+func (l *Logger) Warn() *Event {
+	return l.newEvent(WarnLevel, nil)
 }
 
 // Error starts a new message with error level.
 //
 // You must call Msg on the returned event in order to send the event.
-func (l Logger) Error() *Event {
-	return l.newEvent(ErrorLevel, true, nil)
+func (l *Logger) Error() *Event {
+	return l.newEvent(ErrorLevel, nil)
 }
 
 // Fatal starts a new message with fatal level. The os.Exit(1) function
 // is called by the Msg method.
 //
 // You must call Msg on the returned event in order to send the event.
-func (l Logger) Fatal() *Event {
-	return l.newEvent(FatalLevel, true, func(msg string) { os.Exit(1) })
+func (l *Logger) Fatal() *Event {
+	return l.newEvent(FatalLevel, func(msg string) { os.Exit(1) })
 }
 
 // Panic starts a new message with panic level. The message is also sent
 // to the panic function.
 //
 // You must call Msg on the returned event in order to send the event.
-func (l Logger) Panic() *Event {
-	return l.newEvent(PanicLevel, true, func(msg string) { panic(msg) })
+func (l *Logger) Panic() *Event {
+	return l.newEvent(PanicLevel, func(msg string) { panic(msg) })
+}
+
+// WithLevel starts a new message with level.
+//
+// You must call Msg on the returned event in order to send the event.
+func (l *Logger) WithLevel(level Level) *Event {
+	switch level {
+	case DebugLevel:
+		return l.Debug()
+	case InfoLevel:
+		return l.Info()
+	case WarnLevel:
+		return l.Warn()
+	case ErrorLevel:
+		return l.Error()
+	case FatalLevel:
+		return l.Fatal()
+	case PanicLevel:
+		return l.Panic()
+	case NoLevel:
+		return l.Log()
+	case Disabled:
+		return nil
+	default:
+		panic("zerolog: WithLevel(): invalid level: " + strconv.Itoa(int(level)))
+	}
 }
 
 // Log starts a new message with no level. Setting GlobalLevel to Disabled
 // will still disable events produced by this method.
 //
 // You must call Msg on the returned event in order to send the event.
-func (l Logger) Log() *Event {
-	// We use panic level with addLevelField=false to make Log passthrough all
-	// levels except Disabled.
-	return l.newEvent(PanicLevel, false, nil)
+func (l *Logger) Log() *Event {
+	return l.newEvent(NoLevel, nil)
+}
+
+// Print sends a log event using debug level and no extra field.
+// Arguments are handled in the manner of fmt.Print.
+func (l *Logger) Print(v ...interface{}) {
+	if e := l.Debug(); e.Enabled() {
+		e.Msg(fmt.Sprint(v...))
+	}
+}
+
+// Printf sends a log event using debug level and no extra field.
+// Arguments are handled in the manner of fmt.Printf.
+func (l *Logger) Printf(format string, v ...interface{}) {
+	if e := l.Debug(); e.Enabled() {
+		e.Msg(fmt.Sprintf(format, v...))
+	}
 }
 
 // Write implements the io.Writer interface. This is useful to set as a writer
@@ -268,44 +338,39 @@ func (l Logger) Write(p []byte) (n int, err error) {
 	return
 }
 
-func (l Logger) newEvent(level Level, addLevelField bool, done func(string)) *Event {
+func (l *Logger) newEvent(level Level, done func(string)) *Event {
 	enabled := l.should(level)
 	if !enabled {
-		return disabledEvent
+		return nil
 	}
-	lvl := InfoLevel
-	if addLevelField {
-		lvl = level
-	}
-	e := newEvent(l.w, lvl, enabled)
+	e := newEvent(l.w, level, true)
 	e.done = done
 	if l.context != nil && len(l.context) > 0 && l.context[0] > 0 {
 		// first byte of context is ts flag
-		e.buf = appendTimestamp(e.buf)
+		e.buf = json.AppendTime(json.AppendKey(e.buf, TimestampFieldName), TimestampFunc(), TimeFieldFormat)
 	}
-	if addLevelField {
+	if level != NoLevel {
 		e.Str(LevelFieldName, level.String())
 	}
-	if l.sample > 0 && SampleFieldName != "" {
-		e.Uint32(SampleFieldName, l.sample)
-	}
 	if l.context != nil && len(l.context) > 1 {
 		if len(e.buf) > 1 {
 			e.buf = append(e.buf, ',')
 		}
 		e.buf = append(e.buf, l.context[1:]...)
 	}
+	if len(l.hooks) > 0 {
+		e.h = append(e.h, l.hooks...)
+	}
 	return e
 }
 
 // should returns true if the log event should be logged.
-func (l Logger) should(lvl Level) bool {
+func (l *Logger) should(lvl Level) bool {
 	if lvl < l.level || lvl < globalLevel() {
 		return false
 	}
-	if l.sample > 0 && l.counter != nil && !samplingDisabled() {
-		c := atomic.AddUint32(l.counter, 1)
-		return c%l.sample == 0
+	if l.sampler != nil && !samplingDisabled() {
+		return l.sampler.Sample(lvl)
 	}
 	return true
 }

log/log.go

@@ -3,6 +3,7 @@ package log
 
 import (
 	"context"
+	"io"
 	"os"
 
 	"github.com/rs/zerolog"
@@ -11,6 +12,11 @@ import (
 // Logger is the global logger.
 var Logger = zerolog.New(os.Stderr).With().Timestamp().Logger()
 
+// Output duplicates the global logger and sets w as its output.
+func Output(w io.Writer) zerolog.Logger {
+	return Logger.Output(w)
+}
+
 // With creates a child logger with the field added to its context.
 func With() zerolog.Context {
 	return Logger.With()
@@ -21,9 +27,14 @@ func Level(level zerolog.Level) zerolog.Logger {
 	return Logger.Level(level)
 }
 
-// Sample returns a logger that only let one message out of every to pass thru.
-func Sample(every int) zerolog.Logger {
-	return Logger.Sample(every)
+// Sample returns a logger with the s sampler.
+func Sample(s zerolog.Sampler) zerolog.Logger {
+	return Logger.Sample(s)
+}
+
+// Hook returns a logger with the h Hook.
+func Hook(h zerolog.Hook) zerolog.Logger {
+	return Logger.Hook(h)
 }
 
 // Debug starts a new message with debug level.
@@ -70,6 +81,13 @@ func Panic() *zerolog.Event {
 	return Logger.Panic()
 }
 
+// WithLevel starts a new message with level.
+//
+// You must call Msg on the returned event in order to send the event.
+func WithLevel(level zerolog.Level) *zerolog.Event {
+	return Logger.WithLevel(level)
+}
+
 // Log starts a new message with no level. Setting zerolog.GlobalLevel to
 // zerlog.Disabled will still disable events produced by this method.
 //
@@ -78,8 +96,20 @@ func Log() *zerolog.Event {
 	return Logger.Log()
 }
 
+// Print sends a log event using debug level and no extra field.
+// Arguments are handled in the manner of fmt.Print.
+func Print(v ...interface{}) {
+	Logger.Print(v...)
+}
+
+// Printf sends a log event using debug level and no extra field.
+// Arguments are handled in the manner of fmt.Printf.
+func Printf(format string, v ...interface{}) {
+	Logger.Printf(format, v...)
+}
+
 // Ctx returns the Logger associated with the ctx. If no logger
 // is associated, a disabled logger is returned.
-func Ctx(ctx context.Context) zerolog.Logger {
+func Ctx(ctx context.Context) *zerolog.Logger {
 	return zerolog.Ctx(ctx)
 }

log_example_test.go

@@ -38,15 +38,58 @@ func ExampleLogger_Level() {
 }
 
 func ExampleLogger_Sample() {
-	log := zerolog.New(os.Stdout).Sample(2)
+	log := zerolog.New(os.Stdout).Sample(&zerolog.BasicSampler{N: 2})
 
 	log.Info().Msg("message 1")
 	log.Info().Msg("message 2")
 	log.Info().Msg("message 3")
 	log.Info().Msg("message 4")
 
-	// Output: {"level":"info","sample":2,"message":"message 2"}
-	// {"level":"info","sample":2,"message":"message 4"}
+	// Output: {"level":"info","message":"message 2"}
+	// {"level":"info","message":"message 4"}
+}
+
+type LevelNameHook struct{}
+
+func (h LevelNameHook) Run(e *zerolog.Event, l zerolog.Level, msg string) {
+	if l != zerolog.NoLevel {
+		e.Str("level_name", l.String())
+	} else {
+		e.Str("level_name", "NoLevel")
+	}
+}
+
+type MessageHook string
+
+func (h MessageHook) Run(e *zerolog.Event, l zerolog.Level, msg string) {
+	e.Str("the_message", msg)
+}
+
+func ExampleLogger_Hook() {
+	var levelNameHook LevelNameHook
+	var messageHook MessageHook = "The message"
+
+	log := zerolog.New(os.Stdout).Hook(levelNameHook).Hook(messageHook)
+
+	log.Info().Msg("hello world")
+
+	// Output: {"level":"info","level_name":"info","the_message":"hello world","message":"hello world"}
+}
+
+func ExampleLogger_Print() {
+	log := zerolog.New(os.Stdout)
+
+	log.Print("hello world")
+
+	// Output: {"level":"debug","message":"hello world"}
+}
+
+func ExampleLogger_Printf() {
+	log := zerolog.New(os.Stdout)
+
+	log.Printf("hello %s", "world")
+
+	// Output: {"level":"debug","message":"hello world"}
 }
 
 func ExampleLogger_Debug() {
@@ -91,6 +134,15 @@ func ExampleLogger_Error() {
 	// Output: {"level":"error","error":"some error","message":"error doing something"}
 }
 
+func ExampleLogger_WithLevel() {
+	log := zerolog.New(os.Stdout)
+
+	log.WithLevel(zerolog.InfoLevel).
+		Msg("hello world")
+
+	// Output: {"level":"info","message":"hello world"}
+}
+
 func ExampleLogger_Write() {
 	log := zerolog.New(os.Stdout).With().
 		Str("foo", "bar").
@@ -129,6 +181,71 @@ func ExampleEvent_Dict() {
 	// Output: {"foo":"bar","dict":{"bar":"baz","n":1},"message":"hello world"}
 }
 
+type User struct {
+	Name    string
+	Age     int
+	Created time.Time
+}
+
+func (u User) MarshalZerologObject(e *zerolog.Event) {
+	e.Str("name", u.Name).
+		Int("age", u.Age).
+		Time("created", u.Created)
+}
+
+type Users []User
+
+func (uu Users) MarshalZerologArray(a *zerolog.Array) {
+	for _, u := range uu {
+		a.Object(u)
+	}
+}
+
+func ExampleEvent_Array() {
+	log := zerolog.New(os.Stdout)
+
+	log.Log().
+		Str("foo", "bar").
+		Array("array", zerolog.Arr().
+			Str("baz").
+			Int(1),
+		).
+		Msg("hello world")
+
+	// Output: {"foo":"bar","array":["baz",1],"message":"hello world"}
+}
+
+func ExampleEvent_Array_object() {
+	log := zerolog.New(os.Stdout)
+
+	// Users implements zerolog.LogArrayMarshaler
+	u := Users{
+		User{"John", 35, time.Time{}},
+		User{"Bob", 55, time.Time{}},
+	}
+
+	log.Log().
+		Str("foo", "bar").
+		Array("users", u).
+		Msg("hello world")
+
+	// Output: {"foo":"bar","users":[{"name":"John","age":35,"created":"0001-01-01T00:00:00Z"},{"name":"Bob","age":55,"created":"0001-01-01T00:00:00Z"}],"message":"hello world"}
+}
+
+func ExampleEvent_Object() {
+	log := zerolog.New(os.Stdout)
+
+	// User implements zerolog.LogObjectMarshaler
+	u := User{"John", 35, time.Time{}}
+
+	log.Log().
+		Str("foo", "bar").
+		Object("user", u).
+		Msg("hello world")
+
+	// Output: {"foo":"bar","user":{"name":"John","age":35,"created":"0001-01-01T00:00:00Z"},"message":"hello world"}
+}
+
 func ExampleEvent_Interface() {
 	log := zerolog.New(os.Stdout)
 
@@ -159,6 +276,22 @@ func ExampleEvent_Dur() {
 	// Output: {"foo":"bar","dur":10000,"message":"hello world"}
 }
 
+func ExampleEvent_Durs() {
+	d := []time.Duration{
+		time.Duration(10 * time.Second),
+		time.Duration(20 * time.Second),
+	}
+
+	log := zerolog.New(os.Stdout)
+
+	log.Log().
+		Str("foo", "bar").
+		Durs("durs", d).
+		Msg("hello world")
+
+	// Output: {"foo":"bar","durs":[10000,20000],"message":"hello world"}
+}
+
 func ExampleContext_Dict() {
 	log := zerolog.New(os.Stdout).With().
 		Str("foo", "bar").
@@ -172,6 +305,50 @@ func ExampleContext_Dict() {
 	// Output: {"foo":"bar","dict":{"bar":"baz","n":1},"message":"hello world"}
 }
 
+func ExampleContext_Array() {
+	log := zerolog.New(os.Stdout).With().
+		Str("foo", "bar").
+		Array("array", zerolog.Arr().
+			Str("baz").
+			Int(1),
+		).Logger()
+
+	log.Log().Msg("hello world")
+
+	// Output: {"foo":"bar","array":["baz",1],"message":"hello world"}
+}
+
+func ExampleContext_Array_object() {
+	// Users implements zerolog.LogArrayMarshaler
+	u := Users{
+		User{"John", 35, time.Time{}},
+		User{"Bob", 55, time.Time{}},
+	}
+
+	log := zerolog.New(os.Stdout).With().
+		Str("foo", "bar").
+		Array("users", u).
+		Logger()
+
+	log.Log().Msg("hello world")
+
+	// Output: {"foo":"bar","users":[{"name":"John","age":35,"created":"0001-01-01T00:00:00Z"},{"name":"Bob","age":55,"created":"0001-01-01T00:00:00Z"}],"message":"hello world"}
+}
+
+func ExampleContext_Object() {
+	// User implements zerolog.LogObjectMarshaler
+	u := User{"John", 35, time.Time{}}
+
+	log := zerolog.New(os.Stdout).With().
+		Str("foo", "bar").
+		Object("user", u).
+		Logger()
+
+	log.Log().Msg("hello world")
+
+	// Output: {"foo":"bar","user":{"name":"John","age":35,"created":"0001-01-01T00:00:00Z"},"message":"hello world"}
+}
+
 func ExampleContext_Interface() {
 	obj := struct {
 		Name string `json:"name"`
@@ -201,3 +378,19 @@ func ExampleContext_Dur() {
 
 	// Output: {"foo":"bar","dur":10000,"message":"hello world"}
 }
+
+func ExampleContext_Durs() {
+	d := []time.Duration{
+		time.Duration(10 * time.Second),
+		time.Duration(20 * time.Second),
+	}
+
+	log := zerolog.New(os.Stdout).With().
+		Str("foo", "bar").
+		Durs("durs", d).
+		Logger()
+
+	log.Log().Msg("hello world")
+
+	// Output: {"foo":"bar","durs":[10000,20000],"message":"hello world"}
+}

log_test.go

@@ -14,7 +14,7 @@ func TestLog(t *testing.T) {
 		log := New(out)
 		log.Log().Msg("")
 		if got, want := out.String(), "{}\n"; got != want {
-			t.Errorf("invalid log output: got %q, want %q", got, want)
+			t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
 		}
 	})
 
@@ -23,7 +23,7 @@ func TestLog(t *testing.T) {
 		log := New(out)
 		log.Log().Str("foo", "bar").Msg("")
 		if got, want := out.String(), `{"foo":"bar"}`+"\n"; got != want {
-			t.Errorf("invalid log output: got %q, want %q", got, want)
+			t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
 		}
 	})
 
@@ -35,7 +35,7 @@ func TestLog(t *testing.T) {
 			Int("n", 123).
 			Msg("")
 		if got, want := out.String(), `{"foo":"bar","n":123}`+"\n"; got != want {
-			t.Errorf("invalid log output: got %q, want %q", got, want)
+			t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
 		}
 	})
 }
@@ -46,7 +46,7 @@ func TestInfo(t *testing.T) {
 		log := New(out)
 		log.Info().Msg("")
 		if got, want := out.String(), `{"level":"info"}`+"\n"; got != want {
-			t.Errorf("invalid log output: got %q, want %q", got, want)
+			t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
 		}
 	})
 
@@ -55,7 +55,7 @@ func TestInfo(t *testing.T) {
 		log := New(out)
 		log.Info().Str("foo", "bar").Msg("")
 		if got, want := out.String(), `{"level":"info","foo":"bar"}`+"\n"; got != want {
-			t.Errorf("invalid log output: got %q, want %q", got, want)
+			t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
 		}
 	})
 
@@ -67,7 +67,7 @@ func TestInfo(t *testing.T) {
 			Int("n", 123).
 			Msg("")
 		if got, want := out.String(), `{"level":"info","foo":"bar","n":123}`+"\n"; got != want {
-			t.Errorf("invalid log output: got %q, want %q", got, want)
+			t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
 		}
 	})
 }
@@ -95,15 +95,46 @@ func TestWith(t *testing.T) {
 		Logger()
 	log.Log().Msg("")
 	if got, want := out.String(), `{"foo":"bar","error":"some error","bool":true,"int":1,"int8":2,"int16":3,"int32":4,"int64":5,"uint":6,"uint8":7,"uint16":8,"uint32":9,"uint64":10,"float32":11,"float64":12,"time":"0001-01-01T00:00:00Z"}`+"\n"; got != want {
-		t.Errorf("invalid log output: got %q, want %q", got, want)
+		t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
+	}
+}
+
+func TestFieldsMap(t *testing.T) {
+	out := &bytes.Buffer{}
+	log := New(out)
+	log.Log().Fields(map[string]interface{}{
+		"nil":     nil,
+		"string":  "foo",
+		"bytes":   []byte("bar"),
+		"error":   errors.New("some error"),
+		"bool":    true,
+		"int":     int(1),
+		"int8":    int8(2),
+		"int16":   int16(3),
+		"int32":   int32(4),
+		"int64":   int64(5),
+		"uint":    uint(6),
+		"uint8":   uint8(7),
+		"uint16":  uint16(8),
+		"uint32":  uint32(9),
+		"uint64":  uint64(10),
+		"float32": float32(11),
+		"float64": float64(12),
+		"dur":     1 * time.Second,
+		"time":    time.Time{},
+	}).Msg("")
+	if got, want := out.String(), `{"bool":true,"bytes":"bar","dur":1000,"error":"some error","float32":11,"float64":12,"int":1,"int16":3,"int32":4,"int64":5,"int8":2,"nil":null,"string":"foo","time":"0001-01-01T00:00:00Z","uint":6,"uint16":8,"uint32":9,"uint64":10,"uint8":7}`+"\n"; got != want {
+		t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
 	}
 }
 
 func TestFields(t *testing.T) {
 	out := &bytes.Buffer{}
 	log := New(out)
+	now := time.Now()
 	log.Log().
-		Str("foo", "bar").
+		Str("string", "foo").
+		Bytes("bytes", []byte("bar")).
 		AnErr("some_err", nil).
 		Err(errors.New("some error")).
 		Bool("bool", true).
@@ -121,18 +152,101 @@ func TestFields(t *testing.T) {
 		Float64("float64", 12).
 		Dur("dur", 1*time.Second).
 		Time("time", time.Time{}).
-		TimeDiff("diff", time.Now(), time.Now().Add(-10*time.Second)).
+		TimeDiff("diff", now, now.Add(-10*time.Second)).
 		Msg("")
-	if got, want := out.String(), `{"foo":"bar","error":"some error","bool":true,"int":1,"int8":2,"int16":3,"int32":4,"int64":5,"uint":6,"uint8":7,"uint16":8,"uint32":9,"uint64":10,"float32":11,"float64":12,"dur":1000,"time":"0001-01-01T00:00:00Z","diff":10000}`+"\n"; got != want {
-		t.Errorf("invalid log output: got %q, want %q", got, want)
+	if got, want := out.String(), `{"string":"foo","bytes":"bar","error":"some error","bool":true,"int":1,"int8":2,"int16":3,"int32":4,"int64":5,"uint":6,"uint8":7,"uint16":8,"uint32":9,"uint64":10,"float32":11,"float64":12,"dur":1000,"time":"0001-01-01T00:00:00Z","diff":10000}`+"\n"; got != want {
+		t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
+	}
+}
+
+func TestFieldsArrayEmpty(t *testing.T) {
+	out := &bytes.Buffer{}
+	log := New(out)
+	log.Log().
+		Strs("string", []string{}).
+		Errs("err", []error{}).
+		Bools("bool", []bool{}).
+		Ints("int", []int{}).
+		Ints8("int8", []int8{}).
+		Ints16("int16", []int16{}).
+		Ints32("int32", []int32{}).
+		Ints64("int64", []int64{}).
+		Uints("uint", []uint{}).
+		Uints8("uint8", []uint8{}).
+		Uints16("uint16", []uint16{}).
+		Uints32("uint32", []uint32{}).
+		Uints64("uint64", []uint64{}).
+		Floats32("float32", []float32{}).
+		Floats64("float64", []float64{}).
+		Durs("dur", []time.Duration{}).
+		Times("time", []time.Time{}).
+		Msg("")
+	if got, want := out.String(), `{"string":[],"err":[],"bool":[],"int":[],"int8":[],"int16":[],"int32":[],"int64":[],"uint":[],"uint8":[],"uint16":[],"uint32":[],"uint64":[],"float32":[],"float64":[],"dur":[],"time":[]}`+"\n"; got != want {
+		t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
+	}
+}
+
+func TestFieldsArraySingleElement(t *testing.T) {
+	out := &bytes.Buffer{}
+	log := New(out)
+	log.Log().
+		Strs("string", []string{"foo"}).
+		Errs("err", []error{errors.New("some error")}).
+		Bools("bool", []bool{true}).
+		Ints("int", []int{1}).
+		Ints8("int8", []int8{2}).
+		Ints16("int16", []int16{3}).
+		Ints32("int32", []int32{4}).
+		Ints64("int64", []int64{5}).
+		Uints("uint", []uint{6}).
+		Uints8("uint8", []uint8{7}).
+		Uints16("uint16", []uint16{8}).
+		Uints32("uint32", []uint32{9}).
+		Uints64("uint64", []uint64{10}).
+		Floats32("float32", []float32{11}).
+		Floats64("float64", []float64{12}).
+		Durs("dur", []time.Duration{1 * time.Second}).
+		Times("time", []time.Time{time.Time{}}).
+		Msg("")
+	if got, want := out.String(), `{"string":["foo"],"err":["some error"],"bool":[true],"int":[1],"int8":[2],"int16":[3],"int32":[4],"int64":[5],"uint":[6],"uint8":[7],"uint16":[8],"uint32":[9],"uint64":[10],"float32":[11],"float64":[12],"dur":[1000],"time":["0001-01-01T00:00:00Z"]}`+"\n"; got != want {
+		t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
+	}
+}
+
+func TestFieldsArrayMultipleElement(t *testing.T) {
+	out := &bytes.Buffer{}
+	log := New(out)
+	log.Log().
+		Strs("string", []string{"foo", "bar"}).
+		Errs("err", []error{errors.New("some error"), nil}).
+		Bools("bool", []bool{true, false}).
+		Ints("int", []int{1, 0}).
+		Ints8("int8", []int8{2, 0}).
+		Ints16("int16", []int16{3, 0}).
+		Ints32("int32", []int32{4, 0}).
+		Ints64("int64", []int64{5, 0}).
+		Uints("uint", []uint{6, 0}).
+		Uints8("uint8", []uint8{7, 0}).
+		Uints16("uint16", []uint16{8, 0}).
+		Uints32("uint32", []uint32{9, 0}).
+		Uints64("uint64", []uint64{10, 0}).
+		Floats32("float32", []float32{11, 0}).
+		Floats64("float64", []float64{12, 0}).
+		Durs("dur", []time.Duration{1 * time.Second, 0}).
+		Times("time", []time.Time{time.Time{}, time.Time{}}).
+		Msg("")
+	if got, want := out.String(), `{"string":["foo","bar"],"err":["some error",null],"bool":[true,false],"int":[1,0],"int8":[2,0],"int16":[3,0],"int32":[4,0],"int64":[5,0],"uint":[6,0],"uint8":[7,0],"uint16":[8,0],"uint32":[9,0],"uint64":[10,0],"float32":[11,0],"float64":[12,0],"dur":[1000,0],"time":["0001-01-01T00:00:00Z","0001-01-01T00:00:00Z"]}`+"\n"; got != want {
+		t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
 	}
 }
 
 func TestFieldsDisabled(t *testing.T) {
 	out := &bytes.Buffer{}
 	log := New(out).Level(InfoLevel)
+	now := time.Now()
 	log.Debug().
-		Str("foo", "bar").
+		Str("string", "foo").
+		Bytes("bytes", []byte("bar")).
 		AnErr("some_err", nil).
 		Err(errors.New("some error")).
 		Bool("bool", true).
@@ -150,18 +264,19 @@ func TestFieldsDisabled(t *testing.T) {
 		Float64("float64", 12).
 		Dur("dur", 1*time.Second).
 		Time("time", time.Time{}).
-		TimeDiff("diff", time.Now(), time.Now().Add(-10*time.Second)).
+		TimeDiff("diff", now, now.Add(-10*time.Second)).
 		Msg("")
 	if got, want := out.String(), ""; got != want {
-		t.Errorf("invalid log output: got %q, want %q", got, want)
+		t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
 	}
 }
 
 func TestMsgf(t *testing.T) {
 	out := &bytes.Buffer{}
-	New(out).Log().Msgf("one %s %.1f %d %v", "two", 3.4, 5, errors.New("six"))
+	log := New(out)
+	log.Log().Msgf("one %s %.1f %d %v", "two", 3.4, 5, errors.New("six"))
 	if got, want := out.String(), `{"message":"one two 3.4 5 six"}`+"\n"; got != want {
-		t.Errorf("invalid log output: got %q, want %q", got, want)
+		t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
 	}
 }
 
@@ -170,7 +285,7 @@ func TestWithAndFieldsCombined(t *testing.T) {
 	log := New(out).With().Str("f1", "val").Str("f2", "val").Logger()
 	log.Log().Str("f3", "val").Msg("")
 	if got, want := out.String(), `{"f1":"val","f2":"val","f3":"val"}`+"\n"; got != want {
-		t.Errorf("invalid log output: got %q, want %q", got, want)
+		t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
 	}
 }
 
@@ -180,7 +295,43 @@ func TestLevel(t *testing.T) {
 		log := New(out).Level(Disabled)
 		log.Info().Msg("test")
 		if got, want := out.String(), ""; got != want {
-			t.Errorf("invalid log output: got %q, want %q", got, want)
+			t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
+		}
+	})
+
+	t.Run("NoLevel/Disabled", func(t *testing.T) {
+		out := &bytes.Buffer{}
+		log := New(out).Level(Disabled)
+		log.Log().Msg("test")
+		if got, want := out.String(), ""; got != want {
+			t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
+		}
+	})
+
+	t.Run("NoLevel/Info", func(t *testing.T) {
+		out := &bytes.Buffer{}
+		log := New(out).Level(InfoLevel)
+		log.Log().Msg("test")
+		if got, want := out.String(), `{"message":"test"}`+"\n"; got != want {
+			t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
+		}
+	})
+
+	t.Run("NoLevel/Panic", func(t *testing.T) {
+		out := &bytes.Buffer{}
+		log := New(out).Level(PanicLevel)
+		log.Log().Msg("test")
+		if got, want := out.String(), `{"message":"test"}`+"\n"; got != want {
+			t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
+		}
+	})
+
+	t.Run("NoLevel/WithLevel", func(t *testing.T) {
+		out := &bytes.Buffer{}
+		log := New(out).Level(InfoLevel)
+		log.WithLevel(NoLevel).Msg("test")
+		if got, want := out.String(), `{"message":"test"}`+"\n"; got != want {
+			t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
 		}
 	})
 
@@ -189,20 +340,20 @@ func TestLevel(t *testing.T) {
 		log := New(out).Level(InfoLevel)
 		log.Info().Msg("test")
 		if got, want := out.String(), `{"level":"info","message":"test"}`+"\n"; got != want {
-			t.Errorf("invalid log output: got %q, want %q", got, want)
+			t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
 		}
 	})
 }
 
 func TestSampling(t *testing.T) {
 	out := &bytes.Buffer{}
-	log := New(out).Sample(2)
+	log := New(out).Sample(&BasicSampler{N: 2})
 	log.Log().Int("i", 1).Msg("")
 	log.Log().Int("i", 2).Msg("")
 	log.Log().Int("i", 3).Msg("")
 	log.Log().Int("i", 4).Msg("")
-	if got, want := out.String(), "{\"sample\":2,\"i\":2}\n{\"sample\":2,\"i\":4}\n"; got != want {
-		t.Errorf("invalid log output: got %q, want %q", got, want)
+	if got, want := out.String(), "{\"i\":2}\n{\"i\":4}\n"; got != want {
+		t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
 	}
 }
 
@@ -237,6 +388,13 @@ func TestLevelWriter(t *testing.T) {
 	log.Info().Msg("2")
 	log.Warn().Msg("3")
 	log.Error().Msg("4")
+	log.Log().Msg("nolevel-1")
+	log.WithLevel(DebugLevel).Msg("5")
+	log.WithLevel(InfoLevel).Msg("6")
+	log.WithLevel(WarnLevel).Msg("7")
+	log.WithLevel(ErrorLevel).Msg("8")
+	log.WithLevel(NoLevel).Msg("nolevel-2")
+
 	want := []struct {
 		l Level
 		p string
@@ -245,6 +403,12 @@ func TestLevelWriter(t *testing.T) {
 		{InfoLevel, `{"level":"info","message":"2"}` + "\n"},
 		{WarnLevel, `{"level":"warn","message":"3"}` + "\n"},
 		{ErrorLevel, `{"level":"error","message":"4"}` + "\n"},
+		{NoLevel, `{"message":"nolevel-1"}` + "\n"},
+		{DebugLevel, `{"level":"debug","message":"5"}` + "\n"},
+		{InfoLevel, `{"level":"info","message":"6"}` + "\n"},
+		{WarnLevel, `{"level":"warn","message":"7"}` + "\n"},
+		{ErrorLevel, `{"level":"error","message":"8"}` + "\n"},
+		{NoLevel, `{"message":"nolevel-2"}` + "\n"},
 	}
 	if got := lw.ops; !reflect.DeepEqual(got, want) {
 		t.Errorf("invalid ops:\ngot:\n%v\nwant:\n%v", got, want)
@@ -263,7 +427,7 @@ func TestContextTimestamp(t *testing.T) {
 	log.Log().Msg("hello world")
 
 	if got, want := out.String(), `{"time":"2001-02-03T04:05:06Z","foo":"bar","message":"hello world"}`+"\n"; got != want {
-		t.Errorf("invalid log output: got %q, want %q", got, want)
+		t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
 	}
 }
 
@@ -279,6 +443,34 @@ func TestEventTimestamp(t *testing.T) {
 	log.Log().Timestamp().Msg("hello world")
 
 	if got, want := out.String(), `{"foo":"bar","time":"2001-02-03T04:05:06Z","message":"hello world"}`+"\n"; got != want {
-		t.Errorf("invalid log output: got %q, want %q", got, want)
+		t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
+	}
+}
+
+func TestOutputWithoutTimestamp(t *testing.T) {
+	ignoredOut := &bytes.Buffer{}
+	out := &bytes.Buffer{}
+	log := New(ignoredOut).Output(out).With().Str("foo", "bar").Logger()
+	log.Log().Msg("hello world")
+
+	if got, want := out.String(), `{"foo":"bar","message":"hello world"}`+"\n"; got != want {
+		t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
+	}
+}
+
+func TestOutputWithTimestamp(t *testing.T) {
+	TimestampFunc = func() time.Time {
+		return time.Date(2001, time.February, 3, 4, 5, 6, 7, time.UTC)
+	}
+	defer func() {
+		TimestampFunc = time.Now
+	}()
+	ignoredOut := &bytes.Buffer{}
+	out := &bytes.Buffer{}
+	log := New(ignoredOut).Output(out).With().Timestamp().Str("foo", "bar").Logger()
+	log.Log().Msg("hello world")
+
+	if got, want := out.String(), `{"time":"2001-02-03T04:05:06Z","foo":"bar","message":"hello world"}`+"\n"; got != want {
+		t.Errorf("invalid log output:\ngot:  %v\nwant: %v", got, want)
 	}
 }

sampler.go

@@ -0,0 +1,126 @@
+package zerolog
+
+import (
+	"math/rand"
+	"sync/atomic"
+	"time"
+)
+
+var (
+	// Often samples log every ~ 10 events.
+	Often = RandomSampler(10)
+	// Sometimes samples log every ~ 100 events.
+	Sometimes = RandomSampler(100)
+	// Rarely samples log every ~ 1000 events.
+	Rarely = RandomSampler(1000)
+)
+
+// Sampler defines an interface to a log sampler.
+type Sampler interface {
+	// Sample returns true if the event should be part of the sample, false if
+	// the event should be dropped.
+	Sample(lvl Level) bool
+}
+
+// RandomSampler use a PRNG to randomly sample an event out of N events,
+// regardless of their level.
+type RandomSampler uint32
+
+// Sample implements the Sampler interface.
+func (s RandomSampler) Sample(lvl Level) bool {
+	if s <= 0 {
+		return false
+	}
+	if rand.Intn(int(s)) != 0 {
+		return false
+	}
+	return true
+}
+
+// BasicSampler is a sampler that will send every Nth events, regardless of
+// there level.
+type BasicSampler struct {
+	N       uint32
+	counter uint32
+}
+
+// Sample implements the Sampler interface.
+func (s *BasicSampler) Sample(lvl Level) bool {
+	c := atomic.AddUint32(&s.counter, 1)
+	return c%s.N == 0
+}
+
+// BurstSampler lets Burst events pass per Period then pass the decision to
+// NextSampler. If Sampler is not set, all subsequent events are rejected.
+type BurstSampler struct {
+	// Burst is the maximum number of event per period allowed before calling
+	// NextSampler.
+	Burst uint32
+	// Period defines the burst period. If 0, NextSampler is always called.
+	Period time.Duration
+	// NextSampler is the sampler used after the burst is reached. If nil,
+	// events are always rejected after the burst.
+	NextSampler Sampler
+
+	counter uint32
+	resetAt int64
+}
+
+// Sample implements the Sampler interface.
+func (s *BurstSampler) Sample(lvl Level) bool {
+	if s.Burst > 0 && s.Period > 0 {
+		if s.inc() <= s.Burst {
+			return true
+		}
+	}
+	if s.NextSampler == nil {
+		return false
+	}
+	return s.NextSampler.Sample(lvl)
+}
+
+func (s *BurstSampler) inc() uint32 {
+	now := time.Now().UnixNano()
+	resetAt := atomic.LoadInt64(&s.resetAt)
+	var c uint32
+	if now > resetAt {
+		c = 1
+		atomic.StoreUint32(&s.counter, c)
+		newResetAt := now + s.Period.Nanoseconds()
+		reset := atomic.CompareAndSwapInt64(&s.resetAt, resetAt, newResetAt)
+		if !reset {
+			// Lost the race with another goroutine trying to reset.
+			c = atomic.AddUint32(&s.counter, 1)
+		}
+	} else {
+		c = atomic.AddUint32(&s.counter, 1)
+	}
+	return c
+}
+
+// LevelSampler applies a different sampler for each level.
+type LevelSampler struct {
+	DebugSampler, InfoSampler, WarnSampler, ErrorSampler Sampler
+}
+
+func (s LevelSampler) Sample(lvl Level) bool {
+	switch lvl {
+	case DebugLevel:
+		if s.DebugSampler != nil {
+			return s.DebugSampler.Sample(lvl)
+		}
+	case InfoLevel:
+		if s.InfoSampler != nil {
+			return s.InfoSampler.Sample(lvl)
+		}
+	case WarnLevel:
+		if s.WarnSampler != nil {
+			return s.WarnSampler.Sample(lvl)
+		}
+	case ErrorLevel:
+		if s.ErrorSampler != nil {
+			return s.ErrorSampler.Sample(lvl)
+		}
+	}
+	return true
+}

sampler_test.go

@@ -0,0 +1,75 @@
+package zerolog
+
+import (
+	"testing"
+	"time"
+)
+
+var samplers = []struct {
+	name    string
+	sampler func() Sampler
+	total   int
+	wantMin int
+	wantMax int
+}{
+	{
+		"BasicSampler",
+		func() Sampler {
+			return &BasicSampler{N: 5}
+		},
+		100, 20, 20,
+	},
+	{
+		"RandomSampler",
+		func() Sampler {
+			return RandomSampler(5)
+		},
+		100, 10, 30,
+	},
+	{
+		"BurstSampler",
+		func() Sampler {
+			return &BurstSampler{Burst: 20, Period: time.Second}
+		},
+		100, 20, 20,
+	},
+	{
+		"BurstSamplerNext",
+		func() Sampler {
+			return &BurstSampler{Burst: 20, Period: time.Second, NextSampler: &BasicSampler{N: 5}}
+		},
+		120, 40, 40,
+	},
+}
+
+func TestSamplers(t *testing.T) {
+	for i := range samplers {
+		s := samplers[i]
+		t.Run(s.name, func(t *testing.T) {
+			sampler := s.sampler()
+			got := 0
+			for t := s.total; t > 0; t-- {
+				if sampler.Sample(0) {
+					got++
+				}
+			}
+			if got < s.wantMin || got > s.wantMax {
+				t.Errorf("%s.Sample(0) == true %d on %d, want [%d, %d]", s.name, got, s.total, s.wantMin, s.wantMax)
+			}
+		})
+	}
+}
+
+func BenchmarkSamplers(b *testing.B) {
+	for i := range samplers {
+		s := samplers[i]
+		b.Run(s.name, func(b *testing.B) {
+			sampler := s.sampler()
+			b.RunParallel(func(pb *testing.PB) {
+				for pb.Next() {
+					sampler.Sample(0)
+				}
+			})
+		})
+	}
+}

syslog.go

@@ -44,6 +44,8 @@ func (sw syslogWriter) WriteLevel(level Level, p []byte) (n int, err error) {
 		err = sw.w.Emerg(string(p))
 	case PanicLevel:
 		err = sw.w.Crit(string(p))
+	case NoLevel:
+		err = sw.w.Info(string(p))
 	default:
 		panic("invalid level")
 	}

syslog_test.go

@@ -1,3 +1,5 @@
+// +build !windows
+
 package zerolog
 
 import "testing"
@@ -46,11 +48,13 @@ func TestSyslogWriter(t *testing.T) {
 	log.Info().Msg("info")
 	log.Warn().Msg("warn")
 	log.Error().Msg("error")
+	log.Log().Msg("nolevel")
 	want := []syslogEvent{
 		{"Debug", `{"level":"debug","message":"debug"}` + "\n"},
 		{"Info", `{"level":"info","message":"info"}` + "\n"},
 		{"Warning", `{"level":"warn","message":"warn"}` + "\n"},
 		{"Err", `{"level":"error","message":"error"}` + "\n"},
+		{"Info", `{"message":"nolevel"}` + "\n"},
 	}
 	if got := sw.events; !reflect.DeepEqual(got, want) {
 		t.Errorf("Invalid syslog message routing: want %v, got %v", want, got)

writer_test.go

@@ -1,3 +1,5 @@
+// +build !windows
+
 package zerolog
 
 import (
@@ -12,11 +14,13 @@ func TestMultiSyslogWriter(t *testing.T) {
 	log.Info().Msg("info")
 	log.Warn().Msg("warn")
 	log.Error().Msg("error")
+	log.Log().Msg("nolevel")
 	want := []syslogEvent{
 		{"Debug", `{"level":"debug","message":"debug"}` + "\n"},
 		{"Info", `{"level":"info","message":"info"}` + "\n"},
 		{"Warning", `{"level":"warn","message":"warn"}` + "\n"},
 		{"Err", `{"level":"error","message":"error"}` + "\n"},
+		{"Info", `{"message":"nolevel"}` + "\n"},
 	}
 	if got := sw.events; !reflect.DeepEqual(got, want) {
 		t.Errorf("Invalid syslog message routing: want %v, got %v", want, got)