Don't join the thread if it hasn't been started

beltran · beltran · commit 4fa014313b68 · 2017-10-03T16:37:27.000-04:00
diff --git a/CHANGELOG.rst b/CHANGELOG.rst
@@ -11,6 +11,7 @@ Bug Fixes
 * Use of DCAwareRoundRobinPolicy raises NoHostAvailable exception (PYTHON-781)
 * Not create two sessions by default in CQLEngine (PYTHON-814)
 * Bug when subclassing AyncoreConnection (PYTHON-827)
+* Rare exception when "sys.exit(0)" after query timeouts (PYTHON-752)
 
 3.11.0
 ======
diff --git a/cassandra/io/libevreactor.py b/cassandra/io/libevreactor.py
@@ -63,6 +63,7 @@ def __init__(self):
         self._started = False
         self._shutdown = False
         self._lock = Lock()
+        self._lock_thread = Lock()
 
         self._thread = None
 
@@ -94,9 +95,11 @@ def maybe_start(self):
                 should_start = True
 
         if should_start:
-            self._thread = Thread(target=self._run_loop, name="event_loop")
-            self._thread.daemon = True
-            self._thread.start()
+            with self._lock_thread:
+                if not self._shutdown:
+                    self._thread = Thread(target=self._run_loop, name="event_loop")
+                    self._thread.daemon = True
+                    self._thread.start()
 
         self._notifier.send()
 
@@ -126,8 +129,11 @@ def _cleanup(self):
                     watcher.stop()
 
         self.notify()  # wake the timer watcher
-        log.debug("Waiting for event loop thread to join...")
-        self._thread.join(timeout=1.0)
+
+        # PYTHON-752 Thread might have just been created and not started
+        with self._lock_thread:
+            self._thread.join(timeout=1.0)
+
         if self._thread.is_alive():
             log.warning(
                 "Event loop thread could not be joined, so shutdown may not be clean. "
