Fix keep_alive running after logout()

_keep_alive_handler would set up another keep alive after the first one
by creating a new threading.Timer object, but Client would only keep
track of the first timer object.  Thus casing the keep alive to continue
running after Client.logout calls cancel() on it's timer object, as it
no longer references the actual timer object waiting for the keep alive.

Fix by replacing _keep_alive_handler with a threading.Thread subclass
that sends keep_alives of the given interval and exits when its stop
event is set.

discord/client.py

@@ -36,7 +36,7 @@ from .invite import Invite
 import requests
 import json, re, time, copy
 from collections import deque
-from threading import Timer
+import threading
 from ws4py.client.threadedclient import WebSocketClient
 import sys
 import logging
@@ -48,20 +48,23 @@ request_success_log = '{name}: {response.url} with {json} received {data}'
 def _null_event(*args, **kwargs):
     pass
 
-def _keep_alive_handler(seconds, ws):
-    def wrapper():
-        _keep_alive_handler(seconds, ws)
-        payload = {
-            'op': 1,
-            'd': int(time.time())
-        }
+class KeepAliveHandler(threading.Thread):
+    def __init__(self, seconds, socket, **kwargs):
+        threading.Thread.__init__(self, **kwargs)
+        self.seconds = seconds
+        self.socket = socket
+        self.stop = threading.Event()
 
-        log.debug('Keeping websocket alive with timestamp {0}'.format(payload['d']))
-        ws.send(json.dumps(payload))
+    def run(self):
+        while not self.stop.wait(self.seconds):
+            payload = {
+                'op': 1,
+                'd': int(time.time())
+            }
 
-    t =  Timer(seconds, wrapper)
-    t.start()
-    return t
+            msg = 'Keeping websocket alive with timestamp {0}'
+            log.debug(msg.format(payload['d']))
+            self.socket.send(json.dumps(payload))
 
 class Client(object):
     """Represents a client connection that connects to Discord.
@@ -229,7 +232,8 @@ class Client(object):
 
             # set the keep alive interval..
             interval = data.get('heartbeat_interval') / 1000.0
-            self.keep_alive = _keep_alive_handler(interval, self.ws)
+            self.keep_alive = KeepAliveHandler(interval, self.ws)
+            self.keep_alive.start()
 
             # we're all ready
             self._invoke_event('on_ready')
@@ -553,7 +557,7 @@ class Client(object):
         response = requests.post(endpoints.LOGOUT)
         self.ws.close()
         self._is_logged_in = False
-        self.keep_alive.cancel()
+        self.keep_alive.stop.set()
         log.debug(request_logging_format.format(name='logout', response=response))
 
     def logs_from(self, channel, limit=500):