Maintain two APNS connections and send correct notifications to each

Now we have 2 different Zulip apps out there, and they are signed with
two certs: Zulip and Dropbox. The Dropbox-signed apps are going to need
to be sent APNS notifications from the appropriate APNS connection

(imported from commit 6db50c5811847db4f08e5c997c7bbb4b46cfc462)

zerver/lib/push_notifications.py

@@ -18,6 +18,13 @@ connection = None
 if settings.APNS_CERT_FILE is not None and os.path.exists(settings.APNS_CERT_FILE):
     connection = session.get_connection(settings.APNS_SANDBOX, cert_file=settings.APNS_CERT_FILE)
 
+# We maintain an additional APNS connection for pushing to Zulip apps that have been signed
+# by the Dropbox certs (and have an app id of com.dropbox.zulip)
+dbx_session = Session()
+dbx_connection = None
+if settings.DBX_APNS_CERT_FILE is not None and os.path.exists(settings.DBX_APNS_CERT_FILE):
+    dbx_connection = session.get_connection(settings.APNS_SANDBOX, cert_file=settings.DBX_APNS_CERT_FILE)
+
 def num_push_devices_for_user(user_profile, kind = None):
     if kind is None:
         return PushDeviceToken.objects.filter(user=user_profile).count()
@@ -31,25 +38,11 @@ def b64_to_hex(data):
 def hex_to_b64(data):
     return base64.b64encode(binascii.unhexlify(data))
 
-# Send a push notification to the desired clients
-# extra_data is a dict that will be passed to the
-# mobile app
-@statsd_increment("apple_push_notification")
-def send_apple_push_notification(user, alert, **extra_data):
-    if not connection:
-        logging.error("Attempting to send push notification, but no connection was found. This may be because we could not find the APNS Certificate file.")
-        return
-
-    b64_tokens = [device.token for device in PushDeviceToken.objects.filter(user=user, kind=PushDeviceToken.APNS)]
-    tokens     = [b64_to_hex(token) for token in b64_tokens]
-
-    logging.info("APNS: Sending apple push notification to devices: %s" % (b64_tokens,))
-    message = Message(tokens, alert=alert, **extra_data)
-
-    apns_client = APNs(connection)
+def _do_push_to_apns_service(user, message, apns_connection):
+    apns_client = APNs(apns_connection)
     ret = apns_client.send(message)
     if not ret:
-       logging.warning("APNS: Failed to send push notification for clients %s" % (b64_tokens,))
+       logging.warning("APNS: Failed to send push notification for clients %s" % (message.tokens,))
        return
 
     for token, reason in ret.failed.items():
@@ -73,6 +66,28 @@ def send_apple_push_notification(user, alert, **extra_data):
             logging.warning("APNS: Unknown error when delivering APNS: %s" %  (errmsg,))
 
 
+# Send a push notification to the desired clients
+# extra_data is a dict that will be passed to the
+# mobile app
+@statsd_increment("apple_push_notification")
+def send_apple_push_notification(user, alert, **extra_data):
+    if not connection and not dbx_connection:
+        logging.error("Attempting to send push notification, but no connection was found. This may be because we could not find the APNS Certificate file.")
+        return
+
+    devices = PushDeviceToken.objects.filter(user=user, kind=PushDeviceToken.APNS)
+    # Plain b64 token kept for debugging purposes
+    tokens = [(b64_to_hex(device.token), device.ios_app_id, device.token) for device in devices]
+
+    logging.info("APNS: Sending apple push notification to devices: %s" % (tokens,))
+    zulip_message = Message([token[0] for token in tokens if token[1] in (settings.ZULIP_IOS_APP_ID, None)],
+                            alert=alert, **extra_data)
+    dbx_message = Message([token[0] for token in tokens if token[1] in (settings.DBX_IOS_APP_ID,)],
+                            alert=alert, **extra_data)
+
+    _do_push_to_apns_service(user, zulip_message, connection)
+    _do_push_to_apns_service(user, dbx_message, dbx_connection)
+
 # NOTE: This is used by the check_apns_tokens manage.py command. Do not call it otherwise, as the
 # feedback() call can take up to 15s
 def check_apns_feedback():