+ +

Presence Router Module

Synapse supports configuring a module that can specify additional users +(local or remote) to should receive certain presence updates from local +users.

Note that routing presence via Application Service transactions is not +currently supported.

The presence routing module is implemented as a Python class, which will +be imported by the running Synapse.

Python Presence Router Class

The Python class is instantiated with two objects:

A configuration object of some type (see below).
An instance of synapse.module_api.ModuleApi.

It then implements methods related to presence routing.

Note that one method of ModuleApi that may be useful is:

async def ModuleApi.send_local_online_presence_to(users: Iterable[str]) -> None
+

which can be given a list of local or remote MXIDs to broadcast known, online user +presence to (for those users that the receiving user is considered interested in). +It does not include state for users who are currently offline, and it can only be +called on workers that support sending federation. Additionally, this method must +only be called from the process that has been configured to write to the +the presence stream. +By default, this is the main process, but another worker can be configured to do +so.

Module structure

Below is a list of possible methods that can be implemented, and whether they are +required.

`parse_config`

def parse_config(config_dict: dict) -> Any
+

Required. A static method that is passed a dictionary of config options, and +should return a validated config object. This method is described further in +Configuration.

`get_users_for_states`

async def get_users_for_states(
+    self,
+    state_updates: Iterable[UserPresenceState],
+) -> Dict[str, Set[UserPresenceState]]:
+

Required. An asynchronous method that is passed an iterable of user presence +state. This method can determine whether a given presence update should be sent to certain +users. It does this by returning a dictionary with keys representing local or remote +Matrix User IDs, and values being a python set +of synapse.handlers.presence.UserPresenceState instances.

Synapse will then attempt to send the specified presence updates to each user when +possible.

`get_interested_users`

async def get_interested_users(self, user_id: str) -> Union[Set[str], str]
+

Required. An asynchronous method that is passed a single Matrix User ID. This +method is expected to return the users that the passed in user may be interested in the +presence of. Returned users may be local or remote. The presence routed as a result of +what this method returns is sent in addition to the updates already sent between users +that share a room together. Presence updates are deduplicated.

This method should return a python set of Matrix User IDs, or the object +synapse.events.presence_router.PresenceRouter.ALL_USERS to indicate that the passed +user should receive presence information for all known users.

For clarity, if the user @alice:example.org is passed to this method, and the Set +{"@bob:example.com", "@charlie:somewhere.org"} is returned, this signifies that Alice +should receive presence updates sent by Bob and Charlie, regardless of whether these +users share a room.

Example

Below is an example implementation of a presence router class.

from typing import Dict, Iterable, Set, Union
+from synapse.events.presence_router import PresenceRouter
+from synapse.handlers.presence import UserPresenceState
+from synapse.module_api import ModuleApi
+
+class PresenceRouterConfig:
+    def __init__(self):
+        # Config options with their defaults
+        # A list of users to always send all user presence updates to
+        self.always_send_to_users = []  # type: List[str]
+        
+        # A list of users to ignore presence updates for. Does not affect
+        # shared-room presence relationships
+        self.blacklisted_users = []  # type: List[str]
+
+class ExamplePresenceRouter:
+    """An example implementation of synapse.presence_router.PresenceRouter.
+    Supports routing all presence to a configured set of users, or a subset
+    of presence from certain users to members of certain rooms.
+
+    Args:
+        config: A configuration object.
+        module_api: An instance of Synapse's ModuleApi.
+    """
+    def __init__(self, config: PresenceRouterConfig, module_api: ModuleApi):
+        self._config = config
+        self._module_api = module_api
+
+    @staticmethod
+    def parse_config(config_dict: dict) -> PresenceRouterConfig:
+        """Parse a configuration dictionary from the homeserver config, do
+        some validation and return a typed PresenceRouterConfig.
+
+        Args:
+            config_dict: The configuration dictionary.
+
+        Returns:
+            A validated config object.
+        """
+        # Initialise a typed config object
+        config = PresenceRouterConfig()
+        always_send_to_users = config_dict.get("always_send_to_users")
+        blacklisted_users = config_dict.get("blacklisted_users")
+
+        # Do some validation of config options... otherwise raise a
+        # synapse.config.ConfigError.
+        config.always_send_to_users = always_send_to_users
+        config.blacklisted_users = blacklisted_users
+
+        return config
+
+    async def get_users_for_states(
+        self,
+        state_updates: Iterable[UserPresenceState],
+    ) -> Dict[str, Set[UserPresenceState]]:
+        """Given an iterable of user presence updates, determine where each one
+        needs to go. Returned results will not affect presence updates that are
+        sent between users who share a room.
+
+        Args:
+            state_updates: An iterable of user presence state updates.
+
+        Returns:
+          A dictionary of user_id -> set of UserPresenceState that the user should 
+          receive.
+        """
+        destination_users = {}  # type: Dict[str, Set[UserPresenceState]
+
+        # Ignore any updates for blacklisted users
+        desired_updates = set()
+        for update in state_updates:
+            if update.state_key not in self._config.blacklisted_users:
+                desired_updates.add(update)
+
+        # Send all presence updates to specific users
+        for user_id in self._config.always_send_to_users:
+            destination_users[user_id] = desired_updates
+
+        return destination_users
+
+    async def get_interested_users(
+        self,
+        user_id: str,
+    ) -> Union[Set[str], PresenceRouter.ALL_USERS]:
+        """
+        Retrieve a list of users that `user_id` is interested in receiving the
+        presence of. This will be in addition to those they share a room with.
+        Optionally, the object PresenceRouter.ALL_USERS can be returned to indicate
+        that this user should receive all incoming local and remote presence updates.
+
+        Note that this method will only be called for local users.
+
+        Args:
+          user_id: A user requesting presence updates.
+
+        Returns:
+          A set of user IDs to return additional presence updates for, or
+          PresenceRouter.ALL_USERS to return presence updates for all other users.
+        """
+        if user_id in self._config.always_send_to_users:
+            return PresenceRouter.ALL_USERS
+
+        return set()
+

A note on `get_users_for_states` and `get_interested_users`

Both of these methods are effectively two different sides of the same coin. The logic +regarding which users should receive updates for other users should be the same +between them.

get_users_for_states is called when presence updates come in from either federation +or local users, and is used to either direct local presence to remote users, or to +wake up the sync streams of local users to collect remote presence.

In contrast, get_interested_users is used to determine the users that presence should +be fetched for when a local user is syncing. This presence is then retrieved, before +being fed through get_users_for_states once again, with only the syncing user's +routing information pulled from the resulting dictionary.

Their routing logic should thus line up, else you may run into unintended behaviour.

Configuration

Once you've crafted your module and installed it into the same Python environment as +Synapse, amend your homeserver config file with the following.

presence:
+  routing_module:
+    module: my_module.ExamplePresenceRouter
+    config:
+      # Any configuration options for your module. The below is an example.
+      # of setting options for ExamplePresenceRouter.
+      always_send_to_users: ["@presence_gobbler:example.org"]
+      blacklisted_users:
+        - "@alice:example.com"
+        - "@bob:example.com"
+      ...
+

The contents of config will be passed as a Python dictionary to the static +parse_config method of your class. The object returned by this method will +then be passed to the __init__ method of your module as config.

+ +