Untested code for polling instances.

api.py

@@ -28,7 +28,11 @@ import config
 
 
 def CreateChannel(google_user, client, client_address, instance_id, args):
-  models.Instance.FindOrCreate(instance_id)
+  instance = models.Instance.FindOrCreate(instance_id)
+
+  if instance.polling:
+    instance.polling = False
+    instance.save()
 
   token = channel.create_channel(
       client_id=instance_id,
@@ -50,6 +54,32 @@ def CreateChannel(google_user, client, client_address, instance_id, args):
   }
 
 
+def Poll(google_user, client, client_address, instance_id, args):
+  instance = models.Instance.FindOrCreate(instance_id)
+
+  if not instance.polling:
+    instance.polling = True
+    instance.save()
+
+  events = []
+  if google_user:
+    events.append({
+      'event_type':  'login',
+      'google_user': google_user.email(),
+    })
+  else:
+    events.append({
+      'event_type': 'logout',
+    })
+
+  for subscription in instance.GetSubscriptions():
+    events.extend(subscription.GetMessages())
+
+  return {
+    'events': events,
+  }
+
+
 def Pin(google_user, client, client_address, instance_id, args):
   instance = models.Instance.FromID(instance_id)
   if not instance or not instance.active:
@@ -143,7 +173,7 @@ def Subscribe(google_user, client, client_address, instance_id, args):
   return {
     'result': 'ok',
     'events': models.Subscription.FindOrCreate(
-        subject, client, instance, args['subject'], messages, last_id),
+        subject, client, instance, args['subject'], messages, last_id, instance.polling),
   }
 
 
@@ -181,6 +211,7 @@ class APIWrapper(webapp2.RequestHandler):
   _COMMANDS = {
       'createChannel': CreateChannel,
       'pin': Pin,
+      'poll': Poll,
       'sendMessage': SendMessage,
       'subscribe': Subscribe,
       'unpin': Unpin,

lib/models.py

@@ -36,6 +36,7 @@ import utils
 # ↳ Message
 # ↳ Pin (⤴︎ Instance)
 # ↳ Subscription (⤴︎ Instance)
+#   ↳ Event
 
 
 class DuplicateMessage(Exception):
@@ -92,6 +93,7 @@ class Client(db.Model):
 class Instance(db.Model):
   # key_name=instance_id
   active = db.BooleanProperty(required=True, default=False)
+  polling = db.BooleanProperty(required=True, default=False)
 
   @classmethod
   def FromID(cls, instance_id):
@@ -99,9 +101,14 @@ class Instance(db.Model):
     return cls.get_by_key_name(instance_id)
 
   @classmethod
-  def FindOrCreate(cls, instance_id):
+  def FindOrCreate(cls, instance_id, polling=False):
     logging.info('Instance: %s', instance_id)
-    return cls.get_or_insert(instance_id)
+    return cls.get_or_insert(instance_id, polling=polling)
+
+  def GetSubscriptions(self):
+    return (
+        Subscription.all()
+        .filter('instance=', self))
 
 
 class Subject(db.Model):
@@ -386,11 +393,12 @@ class Subscription(db.Model):
   instance = db.ReferenceProperty(reference_class=Instance, required=True)
   readable_only_by_me = db.BooleanProperty(required=True, default=False)
   writable_only_by_me = db.BooleanProperty(required=True, default=False)
+  polling = db.BooleanProperty(required=True, default=False)
 
   @classmethod
   @db.transactional()
   def FindOrCreate(cls, subject, client, instance, request,
-                   messages=0, last_id=None):
+                   messages=0, last_id=None, polling=False):
     readable_only_by_me = (request.get('readable_only_by') == 'me')
     writable_only_by_me = (request.get('writable_only_by') == 'me')
     subscriptions = (
@@ -422,10 +430,30 @@ class Subscription(db.Model):
       subscription.delete()
 
   def SendMessage(self, msg):
-    instance_key = Subscription.instance.get_value_for_datastore(self)
+    encoded = json.dumps(msg, default=utils.EncodeJSON)
-    channel.send_message(
+    if self.polling:
-        str(instance_key.name()),
+      Event(parent=this,
-        json.dumps(msg, default=utils.EncodeJSON))
+            json=encoded).save()
+    else:
+      instance_key = Subscription.instance.get_value_for_datastore(self)
+      channel.send_message(str(instance_key.name()), encoded)
+
+  def GetMessages(self):
+    events = (
+        Event.all()
+        .ancestor(self))
+    return [e.ToEvent() for e in events]
+
+
+class Event(db.Model):
+  # parent=Subscription
+
+  json = db.StringProperty(required=True)
+
+  def ToEvent(self):
+    ret = json.loads(self.json)
+    ret['event_id'] = str(self.key())
+    return ret
 
 
 class Message(db.Model):