mod_cloud_notify

Introduction

This module enables support for sending “push notifications” to clients that need it, typically those running on certain mobile devices.

As well as this module, your client must support push notifications (the apps that need it generally do, of course) and the app developer’s push gateway must be reachable from your Prosody server (this happens over a normal XMPP server-to-server ‘s2s’ connection).

Details

Some platforms, notably Apple’s iOS and many versions of Android, impose limits that prevent applications from running or accessing the network in the background. This makes it difficult or impossible for an XMPP application to remain reliably connected to a server to receive messages.

In order for messaging and other apps to receive notifications, the OS vendors run proprietary servers that their OS maintains a permanent connection to in the background. Then they provide APIs to application developers that allow sending notifications to specific devices via those servers.

When you connect to your server with an app that requires push notifications, it will use this module to set up a “push registration”. When you receive a message but your device is not connected to the server, this module will generate a notification and send it to the push gateway operated by your application’s developers). Their gateway will then connect to your device’s OS vendor and ask them to forward the notification to your device. When your device receives the notification, it will display it or wake up the app so it can connect to XMPP and receive any pending messages.

This protocol is described for developers in XEP-0357: Push Notifications.

For this module to work reliably, you must have mod_smacks, mod_mam and mod_carbons also enabled on your server.

Some clients, notably Siskin and Snikket iOS need some additional extensions that are not currently defined in a standard XEP. To support these clients, see mod_cloud_notify_extensions.

Configuration

Option Default Description
push_notification_important_body New Message! The body text to use when the stanza is important (see above), no message body is sent if this is empty
push_max_errors 16 How much persistent push errors are tolerated before notifications for the identifier in question are disabled
push_max_devices 5 The number of allowed devices per user (the oldest devices are automatically removed if this threshold is reached)
push_max_hibernation_timeout 259200 (72h) Number of seconds to extend the smacks timeout if no push was triggered yet (default: 72 hours)
push_notification_with_body (*) false Whether or not to send the real message body to remote pubsub node. Without end-to-end encryption, enabling this may expose your message contents to your client developers and OS vendor. Not recommended.
push_notification_with_sender (*) false Whether or not to send the real message sender to remote pubsub node. Enabling this may expose your contacts to your client developers and OS vendor. Not recommended.

(*) There are privacy implications for enabling these options.

Internal design notes

App servers are notified about offline messages, messages stored by mod_mam or messages waiting in the smacks queue. The business rules outlined here are all honored1.

To cooperate with mod_smacks this module consumes some events: smacks-ack-delayed, smacks-hibernation-start and smacks-hibernation-end. These events allow this module to send out notifications for messages received while the session is hibernated by mod_smacks or even when smacks acknowledgements for messages are delayed by a certain amount of seconds configurable with the mod_smacks setting smacks_max_ack_delay.

The smacks_max_ack_delay setting allows to send out notifications to clients which aren’t already in smacks hibernation state (because the read timeout or connection close didn’t already happen) but also aren’t responding to acknowledgement request in a timely manner. This setting thus allows conversations to be smoother under such circumstances.

The new event cloud-notify-ping can be used by any module to send out a cloud notification to either all registered endpoints for the given user or only the endpoints given in the event data.

The config setting push_notification_important_body can be used to specify an alternative body text to send to the remote pubsub node if the stanza is encrypted or has a body. This way the real contents of the message aren’t revealed to the push appserver but it can still see that the push is important. This is used by Chatsecure on iOS to send out high priority pushes in those cases for example.

Compatibility

trunk Works
0.12 Works
0.11 Works
0.10 Works
0.9 Support dropped, use last supported version 675726ab06d3

  1. business_rules.markdown↩︎


Installation

With the plugin installer in Prosody 0.12 you can use:

sudo prosodyctl install --server=https://modules.prosody.im/rocks/ mod_cloud_notify

For earlier versions see the documentation for installing 3rd party modules