avro test: wait for mock server start rather than arbitrary sleep

This makes the tests more robust and faster

Author: edenhill

tests/avro/mock_registry.py

@@ -24,7 +24,7 @@
 import json
 import re
 
-from threading import Thread
+from threading import Thread, Event
 
 from tests.avro.mock_schema_registry_client import MockSchemaRegistryClient
 from confluent_kafka import avro
@@ -176,11 +176,18 @@ def __init__(self, port):
         self.server = None
         self.port = port
         self.daemon = True
+        self.started = Event()
 
     def run(self):
         self.server = MockServer(('127.0.0.1', self.port), ReqHandler)
+        self.started.set()
         self.server.serve_forever()
 
+    def start(self):
+        """ Start, and wait for server to be fully started, before returning. """
+        super(ServerThread, self).start()
+        self.started.wait()
+
     def shutdown(self):
         if self.server:
             self.server.shutdown()

tests/avro/test_cached_client.py

@@ -34,7 +34,6 @@ class TestCacheSchemaRegistryClient(unittest.TestCase):
     def setUp(self):
         self.server = mock_registry.ServerThread(0)
         self.server.start()
-        time.sleep(1)
         self.client = CachedSchemaRegistryClient('http://127.0.0.1:' + str(self.server.server.server_port))
 
     def tearDown(self):