From ffab18ee48401e00f339d9d35d3eb78434eff01e Mon Sep 17 00:00:00 2001
From: Giacomo Vercesi <giacomo.vercesi@rev.ng>
Date: Tue, 21 Jun 2022 11:33:11 +0200
Subject: [PATCH] revng daemon: identify valid port

This commit resolves a non-deterministic test failure in `revng daemon`.

When running daemon tests, `randint` was used for selecting the listen
port, this caused test failures when the same port number was used for
reused. This has been replaced with the use of port 0 that guarantees
the use of an unused port and psutil to find the port number once it has
been bound by the daemon process.
---
 python/requirements.txt               |  1 +
 share/revng/test/tests/daemon/test.py | 17 +++++++++++++----
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/python/requirements.txt b/python/requirements.txt
index 9d6a59fc0..421bb5de6 100644
--- a/python/requirements.txt
+++ b/python/requirements.txt
@@ -23,3 +23,4 @@ pytest
 requests
 requests-toolbelt
 gql
+psutil
diff --git a/share/revng/test/tests/daemon/test.py b/share/revng/test/tests/daemon/test.py
index 52752aeb3..6f1b5e69b 100755
--- a/share/revng/test/tests/daemon/test.py
+++ b/share/revng/test/tests/daemon/test.py
@@ -6,7 +6,6 @@
 
 import io
 import os
-from random import randint
 from subprocess import Popen
 from time import sleep
 from typing import Generator
@@ -15,6 +14,7 @@ from urllib.request import urlopen
 
 from gql import Client, gql
 from gql.transport.requests import RequestsHTTPTransport
+from psutil import Process
 from pytest import Config, fixture, mark
 
 
@@ -24,6 +24,16 @@ def print_fd(fd: int):
     print(out_read.read())
 
 
+def get_listen_port(pid: int) -> int:
+    psutil_process = Process(pid)
+    while True:
+        connections = psutil_process.connections()
+        for connection in connections:
+            if connection.raddr == () and connection.status == "LISTEN":
+                return connection.laddr.port
+        sleep(0.5)
+
+
 def check_server_up(port: int):
     for _ in range(10):
         try:
@@ -38,12 +48,11 @@ def check_server_up(port: int):
 
 @fixture
 def client(pytestconfig: Config, request) -> Generator[Client, None, None]:
-    port = randint(20000, 65000)
-
     out_fd = os.memfd_create("flask_debug", 0)
     out = os.fdopen(out_fd, "w")
 
-    process = Popen(["revng", "daemon", "-p", str(port)], stdout=out, stderr=out, text=True)
+    process = Popen(["revng", "daemon", "-p", "0"], stdout=out, stderr=out, text=True)
+    port = get_listen_port(process.pid)
 
     try:
         check_server_up(port)