wait for the flask socket

Author: hackaugusto

raiden/tests/fixtures/api.py

@@ -4,6 +4,8 @@
 
 import os
 import pytest
+import psutil
+import gevent
 from gevent import Greenlet
 
 from raiden.app import App
@@ -14,6 +16,17 @@
 from raiden.tests.utils.apitestcontext import ApiTestContext
 
 
+def wait_for_listening_port(port_number, tries=10, sleep=0.1):
+    for _ in range(tries):
+        gevent.sleep(sleep)
+        connections = psutil.net_connections()
+        for conn in connections:
+            if conn.status == 'LISTEN' and conn.laddr[1] == port_number:
+                return
+
+    raise RuntimeError('{port} is not bound'.format(port_number))
+
+
 # TODO: Figure out why this fixture can't work as session scoped
 #       What happens is that after one test is done, in the next one
 #       the server is no longer running even though the teardown has not
@@ -34,6 +47,11 @@ def api_backend(rest_api_port_number):
         use_evalex=False,
     )
 
+    # Fixes flaky test, were requests are done prior to the server initializing
+    # the listening socket.
+    # https://github.com/raiden-network/raiden/issues/389#issuecomment-305551563
+    wait_for_listening_port(rest_api_port_number)
+
     yield api_server, rest_api
 
     server.kill(block=True, timeout=10)