Log instance IDs in internal channel callbacks.

channel.py

@@ -29,6 +29,7 @@ class OnChannelConnect(webapp2.RequestHandler):
   @db.transactional()
   def post(self):
     instance_id = self.request.get('from')
+    logging.info('Instance: %s', instance_id)
     instance = models.Instance.FromID(instance_id)
     if not instance:
       logging.warning('Channel opened with invalid instance_id: %s', instance_id)
@@ -46,6 +47,7 @@ class OnChannelDisconnect(webapp2.RequestHandler):
   @utils.local_namespace
   def post(self):
     instance_id = self.request.get('from')
+    logging.info('Instance: %s', instance_id)
     instance_key = db.Key.from_path('Instance', instance_id)
 
     subscriptions = list(models.Subscription.all().filter('instance =', instance_key))