Resolve polling issues with feature flags (#29)

* resolve polling issues

* lint

Author: neilkakkar

example.py

@@ -44,4 +44,4 @@
 posthog.set("new_distinct_id", {"current_browser": "Chrome"})
 posthog.set("new_distinct_id", {"current_browser": "Firefox"})
 
-posthog.shutdown()
+# posthog.shutdown()

posthog/client.py

@@ -65,6 +65,7 @@ def __init__(
         self.timeout = timeout
         self.feature_flags = None
         self.poll_interval = poll_interval
+        self.poller = None
 
         # personal_api_key: This should be a generated Personal API Key, private
         self.personal_api_key = personal_api_key
@@ -275,6 +276,9 @@ def join(self):
                 # consumer thread has not started
                 pass
 
+        if self.poller:
+            self.poller.stop()
+
     def shutdown(self):
         """Flush all messages and cleanly shutdown the client"""
         self.flush()
@@ -309,8 +313,9 @@ def load_feature_flags(self):
             return
 
         self._load_feature_flags()
-        poller = Poller(interval=timedelta(seconds=self.poll_interval), execute=self._load_feature_flags)
-        poller.start()
+        if not (self.poller and self.poller.is_alive()):
+            self.poller = Poller(interval=timedelta(seconds=self.poll_interval), execute=self._load_feature_flags)
+            self.poller.start()
 
     def feature_enabled(self, key, distinct_id, default=False):
         require("key", key, string_types)

posthog/poller.py

@@ -4,7 +4,7 @@
 class Poller(threading.Thread):
     def __init__(self, interval, execute, *args, **kwargs):
         threading.Thread.__init__(self)
-        self.daemon = False
+        self.daemon = True  # Make daemon to not interfere with program exit
         self.stopped = threading.Event()
         self.interval = interval
         self.execute = execute