matrix-spec-proposals/specification/modules/push.rst

Push Notifications
==================

.. _module:push:

::

                                   +--------------------+ +-------------------+
                  Matrix HTTP      |                    | |                   |
             Notification Protocol |   App Developer    | |   Device Vendor   |
                                   |                    | |                   |
           +-------------------+   | +----------------+ | | +---------------+ |
           |                   |   | |                | | | |               | |
           | Matrix Home Server+----->  Push Gateway  | +---> Push Provider | |
           |                   |   | |                | | | |               | |
           +-^-----------------+   | +----------------+ | | +----+----------+ |
             |                     |                    | |      |            |
    Matrix   |                     |                    | |      |            |
 Client/Server API  +              |                    | |      |            |
             |      |              +--------------------+ +-------------------+
             |   +--+-+                                          |             
             |   |    <------------------------------------------+             
             +---+    |                                                        
                 |    |          Provider Push Protocol                        
                 +----+                                                        
                                                                               
         Mobile Device or Client                                               


Matrix supports push notifications as a first class citizen. Home Servers send
notifications of user events to user-configured HTTP endpoints. User may also
configure a number of rules that determine what events generate notifications.
These are all stored and managed by the users home server such that settings can
be reused between client apps as appropriate.

The above diagram shows the flow of push notifications being sent to a handset
where push notifications are submitted via the handset vendor, such as Apple's
APNS or Google's GCM. This happens as follows:

 1. The client app signs in to a Matrix Home Server
 2. The client app registers with its vendor's Push Notification provider and
    obtains a routing token of some kind.
 3. The mobile app, uses the Matrix client/server API to add a 'pusher',
    providing the URL of a specific Push Gateway which is configured for that
    application. It also provides the routing token it has acquired from the
    Push Notification Provider.
 4. The Home Server starts sending notification HTTP requests to the Push
    Gateway using the supplied URL. The Push Gateway relays this notification to
    the Push Notification Provider, passing the routing token along with any
    necessary private credentials the provider requires to send push
    notifications.
 5. The Push Notification provider sends the notification to the device.

Definitions for terms used in this section are below:

Pusher
  A 'pusher' is an activity in the Home Server that manages the sending
  of HTTP notifications for a single device of a single user.

Push Rules
  A push rule is a single rule, configured by a matrix user, that gives
  instructions to the Home Server about whether an event should be notified
  about and how given a set of conditions. Matrix clients allow the user to
  configure these. They create and view them via the Client to Server REST API.

Push Gateway
  A push gateway is a server that receives HTTP event notifications from Home
  Servers and passes them on to a different protocol such as APNS for iOS
  devices or GCM for Android devices. Matrix.org provides a reference push
  gateway, 'sygnal'. A client app tells a Home Server what push gateway
  to send notifications to when it sets up a pusher.

For information on the client-server API for setting pushers and push rules, see
the Client Server API section. For more information on the format of HTTP
notifications, see the HTTP Notification Protocol section.

Client behaviour
----------------

To receive any notification pokes at all, it is necessary to configure a
'pusher' on the Home Server that you wish to receive notifications from. There
is a single API endpoint for this, as described below.

{{pusher_http_api}}

Push Rules
~~~~~~~~~~
Homeservers have an interface to configure what events trigger notifications.
This behaviour is configured through "Push Rules". Push Rules come in a variety
of different kinds and each kind of rule has an associated priority. The
different kinds of rule, in descending order of priority, are:

Override Rules
  The highest priority rules are user-configured overrides.
Content Rules
  These configure behaviour for (unencrypted) messages that match certain
  patterns. Content rules take one parameter, 'pattern', that gives the pattern
  to match against. This is treated in the same way as pattern for event_match
  conditions, below.
Room Rules
  These change the behaviour of all messages to a given room. The rule_id of a
  room rule is always the ID of the room that it affects.
Sender
  These rules configure notification behaviour for messages from a specific,
  named Matrix user ID. The rule_id of Sender rules is always the Matrix user
  ID of the user whose messages they'd apply to.
Underride
  These are identical to override rules, but have a lower priority than content,
  room and sender rules.

In addition, each kind of rule may be either global or device-specific. Device
specific rules only affect delivery of notifications via pushers with a matching
``profile_tag``. All device-specific rules are higher priority than all global
rules. Thusly, the full list of rule kinds, in descending priority order, is as
follows:

 * Device-specific Override
 * Device-specific Content
 * Device-specific Room
 * Device-specific Sender
 * Device-specific Underride
 * Global Override
 * Global Content
 * Global Room
 * Global Sender
 * Global Underride

For some kinds of rule, rules of the same kind also have an ordering with
respect to one another. The kinds that do not are room and sender rules where
the rules are mutually exclusive by definition and therefore an ordering would
be redundant. Actions for the highest priority rule and only that rule apply
(for example, a set_tweak action in a lower priority rule will not apply if a
higher priority rule matches, even if that rule does not specify any tweaks).

Rules also have an identifier, ``rule_id``, which is a string. The ``rule_id``
is unique within the kind of rule and scope: ``rule_ids`` need not be unique
between rules of the same kind on different devices. A home server may also have
server default rules of each kind and in each scope. Server default rules are
lower priority than user-defined rules in each scope. Server default rules (and
only server default rules) begin with a dot ('.') character. In addition, all
rules may be enabled or disabled. Disabled rules never match.

If no rules match an event, the Home Server should not notify for the message
(that is to say, the default action is "dont-notify"). Events that the user sent
themselves are never alerted for.

Predefined Rules
++++++++++++++++
Matrix specifies the following rule IDs for server default rules. Home Servers
may define rules as follows with the given IDs. If Home Servers provide rules
with these IDs, their semantics should match those given below:

.m.rule.contains_user_name
  Matches any message whose content is unencrypted and contains the local part
  of the user's Matrix ID, separated by word boundaries.

  Definition (as a content rule)::

    {
        "rule_id": ".m.rule.contains_user_name"
        "pattern": "[the local part of the user's Matrix ID]",
        "actions": [
            "notify",
            {
                "set_tweak": "sound",
                "value": "default"
            }
        ],
    }

.m.rule.contains_display_name
  Matches any message whose content is unencrypted and contains the user's
  current display name in the room in which it was sent.

  Definition (this rule can only be an override or underride rule)::

    {
        "rule_id": ".m.rule.contains_display_name"
        "conditions": [
            {
                "kind": "contains_display_name"
            }
        ],
        "actions": [
            "notify",
            {
                "set_tweak": "sound",
                "value": "default"
            }
        ],
    }

.m.rule.room_one_to_one
  Matches any message sent in a room with exactly two members.

  Definition (this rule can only be an override or underride rule)::

    {
        "rule_id": ".m.rule.room_two_members"
        "conditions": [
            {
                "is": "2",
                "kind": "room_member_count"
            }
        ],
        "actions": [
            "notify",
            {
                "set_tweak": "sound",
                "value": "default"
            }
        ],
    }

.m.rule.suppress_notices
  Matches messages with 'msgtype' of 'notice'. This should be an override rule
  such that, when enabled, it takes priority over content / sender / room rules.

  Definition::

    {
        'rule_id': '.m.rule.suppress_notices',
        'conditions': [
            {
                'kind': 'event_match',
                'key': 'content.msgtype',
                'pattern': 'm.notice',
            }
        ],
        'actions': [
            'dont-notify',
        ]
    }
  
.m.rule.fallback
  Matches any message. Used to define the behaviour of messages that match no
  other rules. Therefore, if Home Servers define this, it should be the lowest
  priority underride rule.

  Definition::

    {
        "rule_id": ".m.rule.fallback"
        "conditions": [],
        "actions": [
            "notify"
        ],
    }

Actions
+++++++
All rules have an associated list of 'actions'. An action affects if and how a
notification is delivered for a matching event. This standard defines the
following actions, although if Home servers wish to support more, they are free
to do so:

notify
  This causes each matching event to generate a notification.
dont_notify
  Prevents this event from generating a notification
coalesce
  This enables notifications for matching events but activates Home Server
  specific behaviour to intelligently coalesce multiple events into a single 
  notification. Not all Home Servers may support this. Those that do not should
  treat it as the 'notify' action.
set_tweak
  Sets an entry in the 'tweaks' dictionary key that is sent in the notification
  poke. This takes the form of a dictionary with a 'set_tweak' key whose value
  is the name of the tweak to set. It may also have a 'value' key which is
  the value to which it should be set.

Actions that have no parameters are represented as a string. Otherwise, they are
represented as a dictionary with a key equal to their name and other keys as
their parameters, e.g. ``{ "set_tweak": "sound", "value": "default" }``

Tweaks
^^^^^^
The ``set_tweak`` key action is used to add an entry to the 'tweaks' dictionary
that is sent in the notification poke. The following tweaks are defined:

sound
  A sound to be played when this notification arrives. 'default' means to
  play a default sound.
highlight
  Whether or not this message should be highlighted in the UI. This will
  normally take the form of presenting the message in a different colour and/or
  weight. The UI might also be adjusted to draw particular attention to the room
  in which the event occurred. The value may be omitted from the highlight
  tweak, in which case it should be read as if it had a value of true.

Tweaks are passed transparently through the Home Server so client applications
and push gateways may agree on additional tweaks, for example, how to flash the
notification light on a mobile device.

If a kind of tweak that a client understands is not specified in an action, the
client may choose a sensible behaviour for the tweak.

Conditions
++++++++++
Override, Underride and Default rules have a list of 'conditions'. All
conditions must hold true for an event in order for a rule to be applied to an
event. A rule with no conditions always matches. Matrix specifies the following
conditions, although if Home Servers wish to support others, they are free to
do so:

event_match
  This is a glob pattern match on a field of the event. Parameters:
   * 'key': The dot-separated field of the event to match, e.g. content.body
   * 'pattern': The glob-style pattern to match against. Patterns with no
                special glob characters should be treated as having asterisks
                prepended and appended when testing the condition.
profile_tag
  Matches the profile_tag of the device that the notification would be
  delivered to. Parameters:

   * 'profile_tag': The profile_tag to match with.
contains_display_name
  This matches unencrypted messages where content.body contains the owner's
  display name in that room. This is a separate rule because display names may
  change and as such it would be hard to maintain a rule that matched the user's
  display name. This condition has no parameters.
room_member_count
  This matches the current number of members in the room.
   * 'is': A decimal integer optionally prefixed by one of, '==', '<', '>',
     '>=' or '<='. A prefix of '<' matches rooms where the member count is
     strictly less than the given number and so forth. If no prefix is present,
     this matches rooms where the member count is exactly equal to the given
     number (i.e. the same as '==').

Room, Sender, User and Content rules do not have conditions in the same way,
but instead have predefined conditions, the behaviour of which can be configured
using parameters named as described above. In the cases of room and sender
rules, the rule_id of the rule determines its behaviour.

Push Rules: API
~~~~~~~~~~~~~~~

Clients can retrieve, add, modify and remove push rules globally or per-device
using the APIs below.

{{pushrules_http_api}}

Examples
++++++++

To create a rule that suppresses notifications for the room with ID
``!dj234r78wl45Gh4D:matrix.org``::

  curl -X PUT -H "Content-Type: application/json" "http://localhost:8008/_matrix/client/api/v1/pushrules/global/room/%21dj234r78wl45Gh4D%3Amatrix.org?access_token=123456" -d \
  '{
     "actions" : ["dont_notify"]
   }' 

To suppress notifications for the user ``@spambot:matrix.org``::

  curl -X PUT -H "Content-Type: application/json" "http://localhost:8008/_matrix/client/api/v1/pushrules/global/sender/%40spambot%3Amatrix.org?access_token=123456" -d \
  '{
     "actions" : ["dont_notify"]
   }' 

To always notify for messages that contain the work 'cake' and set a specific
sound (with a rule_id of ``SSByZWFsbHkgbGlrZSBjYWtl``)::

  curl -X PUT -H "Content-Type: application/json" "http://localhost:8008/_matrix/client/api/v1/pushrules/global/content/SSByZWFsbHkgbGlrZSBjYWtl?access_token=123456" -d \
  '{
     "pattern": "cake",
     "actions" : ["notify", {"set_sound":"cakealarm.wav"}]
   }' 

To add a rule suppressing notifications for messages starting with 'cake' but
ending with 'lie', superseding the previous rule::

  curl -X PUT -H "Content-Type: application/json" "http://localhost:8008/_matrix/client/api/v1/pushrules/global/content/U3BvbmdlIGNha2UgaXMgYmVzdA?access_token=123456&before=SSByZWFsbHkgbGlrZSBjYWtl" -d \
  '{
     "pattern": "cake*lie",
     "actions" : ["notify"]
   }' 

To add a custom sound for notifications messages containing the word 'beer' in
any rooms with 10 members or fewer (with greater importance than the room,
sender and content rules)::

  curl -X PUT -H "Content-Type: application/json" "http://localhost:8008/_matrix/client/api/v1/pushrules/global/override/U2VlIHlvdSBpbiBUaGUgRHVrZQ?access_token=123456" -d \
  '{
     "conditions": [
       {"kind": "event_match", "key": "content.body", "pattern": "beer" },
       {"kind": "room_member_count", "is": "<=10"}
     ],
     "actions" : [
       "notify",
       {"set_sound":"beeroclock.wav"}
     ]
   }' 

Server behaviour
----------------

HTTP Notification Protocol
~~~~~~~~~~~~~~~~~~~~~~~~~~

This describes the format used by "HTTP" pushers to send notifications of
events.

Notifications are sent as HTTP POST requests to the URL configured when the
pusher is created, but Matrix strongly recommends that the path should be::

  /_matrix/push/v1/notify

The body of the POST request is a JSON dictionary. The format
is as follows::

  {
    "notification": {
      "id": "$3957tyerfgewrf384",
      "room_id": "!slw48wfj34rtnrf:example.com",
      "type": "m.room.message",
      "sender": "@exampleuser:matrix.org",
      "sender_display_name": "Major Tom",
      "room_name": "Mission Control",
      "room_alias": "#exampleroom:matrix.org",
      "prio": "high",
      "content": {
        "msgtype": "m.text",
        "body": "I'm floating in a most peculiar way."
      }
     },
     "counts": {
       "unread" : 2,
       "missed_calls": 1
     }
     "devices": [
       {
         "app_id": "org.matrix.matrixConsole.ios",
         "pushkey": "V2h5IG9uIGVhcnRoIGRpZCB5b3UgZGVjb2RlIHRoaXM/",
         "pushkey_ts": 12345678,
         "data" : {
         },
         "tweaks": {
           "sound": "bing"
          }
        }
      ]
    }
  }

The contents of this dictionary are defined as follows:

id
  An identifier for this notification that may be used to detect duplicate
  notification requests. This is not necessarily the ID of the event that
  triggered the notification.
room_id
  The ID of the room in which this event occurred.
type
  The type of the event as in the event's 'type' field.
sender
  The sender of the event as in the corresponding event field.
sender_display_name
  The current display name of the sender in the room in which the event
  occurred.
room_name
  The name of the room in which the event occurred.
room_alias
  An alias to display for the room in which the event occurred.
prio
  The priority of the notification. Acceptable values are 'high' or 'low. If
  omitted, 'high' is assumed. This may be used by push gateways to deliver less
  time-sensitive notifications in a way that will preserve battery power on
  mobile devices.
content
  The 'content' field from the event, if present. If the event had no content
  field, this field is omitted.
counts
  This is a dictionary of the current number of unacknowledged communications
  for the recipient user. Counts whose value is zero are omitted.
unread
  The number of unread messages a user has across all of the rooms they are a
  member of.
missed_calls
  The number of unacknowledged missed calls a user has across all rooms of
  which they are a member.
device
  This is an array of devices that the notification should be sent to.
app_id
  The app_id given when the pusher was created.
pushkey
  The pushkey given when the pusher was created.
pushkey_ts
  The unix timestamp (in seconds) when the pushkey was last updated.
data
  A dictionary of additional pusher-specific data. For 'http' pushers, this is
  the data dictionary passed in at pusher creation minus the 'url' key.
tweaks
  A dictionary of customisations made to the way this notification is to be
  presented. These are added by push rules.
sound
  Sets the sound file that should be played. 'default' means that a default
  sound should be played.

And additional key is defined but only present on member events:

user_is_target
  This is true if the user receiving the notification is the subject of a member
  event (i.e. the state_key of the member event is equal to the user's Matrix
  ID).

The recipient of an HTTP notification should respond with an HTTP 2xx response
when the notification has been processed. If the endpoint returns an HTTP error
code, the Home Server should retry for a reasonable amount of time with a
reasonable back-off scheme.

The endpoint should return a JSON dictionary as follows::

  {
    "rejected": [ "V2h5IG9uIGVhcnRoIGRpZCB5b3UgZGVjb2RlIHRoaXM/" ]
  }

Whose keys are:

rejected
  A list of all pushkeys given in the notification request that are not valid.
  These could have been rejected by an upstream gateway because they have
  expired or have never been valid. Home Servers must cease sending notification
  requests for these pushkeys and remove the associated pushers. It may not
  necessarily be the notification in the request that failed: it could be that
  a previous notification to the same pushkey failed.

Push Gateway behaviour
----------------------

Recommendations for APNS
~~~~~~~~~~~~~~~~~~~~~~~~
For sending APNS notifications, the exact format is flexible and up to the
client app and its push gateway to agree on (since APNS requires that the sender
have a private key owned by the app developer, each app must have its own push
gateway). However, Matrix strongly recommends:

 * That the APNS token be base64 encoded and used as the pushkey.
 * That a different app_id be used for apps on the production and sandbox
   APS environments.
 * That APNS push gateways do not attempt to wait for errors from the APNS
   gateway before returning and instead to store failures and return
   'rejected' responses next time that pushkey is used.

Security considerations
-----------------------

- Message content shouldn't be sent in the push itself as it will pass through
  the Push Provider (Google/Apple). Instead, send a ping to tell the client to
  sync.
- HTTPS should be used on the Matrix HTTP Notification Protocol.