Port the PresenceRouter module interface to the new generic interface

changelog.d/10524.feature

@@ -0,0 +1 @@
+Port the PresenceRouter module interface to the new generic interface.

docs/modules.md

@@ -282,6 +282,49 @@ the request is a server admin.
 Modules can modify the `request_content` (by e.g. adding events to its `initial_state`),
 or deny the room's creation by raising a `module_api.errors.SynapseError`.
 
+#### Presence router callbacks
+
+Presence router callbacks allow module developers to specify additional users (local or remote)
+to receive certain presence updates from local users. Presence router callbacks can be 
+registered using the module API's `register_presence_router_callbacks` method.
+
+The available presence router callbacks are:
+
+```python 
+async def get_users_for_states(
+    self,
+    state_updates: Iterable[UserPresenceState],
+) -> Dict[str, Set[UserPresenceState]]:
+```
+**Requires** `get_interested_users` to also be registered
+
+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.
+
+```python
+async def get_interested_users(self, user_id: str) -> Union[Set[str], str]
+```
+**Requires** `get_users_for_states` to also be registered
+
+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.
+
 
 ### Porting an existing module that uses the old interface
 

docs/presence_router_module.md

@@ -115,11 +115,15 @@ class ExamplePresenceRouter:
 
     Args:
         config: A configuration object.
-        module_api: An instance of Synapse's ModuleApi.
+        api: An instance of Synapse's ModuleApi.
     """
-    def __init__(self, config: PresenceRouterConfig, module_api: ModuleApi):
+    def __init__(self, config: PresenceRouterConfig, api: ModuleApi):
         self._config = config
-        self._module_api = module_api
+        self._module_api = api
+        api.register_presence_router_callbacks(
+          get_users_for_states=self.get_users_for_states,
+          get_interested_users=self.get_interested_users,
+        )
 
     @staticmethod
     def parse_config(config_dict: dict) -> PresenceRouterConfig:
@@ -221,11 +225,8 @@ Once you've crafted your module and installed it into the same Python environmen
 Synapse, amend your homeserver config file with the following.
 
 ```yaml
-presence:
-  enabled: true
-
-  presence_router:
-    module: my_module.ExamplePresenceRouter
+modules:
+  - module: my_module.ExamplePresenceRouter
     config:
       # Any configuration options for your module. The below is an example.
       # of setting options for ExamplePresenceRouter.

docs/sample_config.yaml

@@ -108,20 +108,6 @@ presence:
   #
   #enabled: false
 
-  # Presence routers are third-party modules that can specify additional logic
-  # to where presence updates from users are routed.
-  #
-  presence_router:
-    # The custom module's class. Uncomment to use a custom presence router module.
-    #
-    #module: "my_custom_router.PresenceRouter"
-
-    # Configuration options of the custom module. Refer to your module's
-    # documentation for available options.
-    #
-    #config:
-    #  example_option: 'something'
-
 # Whether to require authentication to retrieve profile data (avatars,
 # display names) of other users through the client API. Defaults to
 # 'false'. Note that profile data is also available via the federation

synapse/app/_base.py

@@ -37,6 +37,7 @@
 from synapse.app.phone_stats_home import start_phone_stats_home
 from synapse.config.homeserver import HomeServerConfig
 from synapse.crypto import context_factory
+from synapse.events.presence_router import load_legacy_presence_router
 from synapse.events.spamcheck import load_legacy_spam_checkers
 from synapse.events.third_party_rules import load_legacy_third_party_event_rules
 from synapse.logging.context import PreserveLoggingContext
@@ -370,6 +371,7 @@ def run_sighup(*args, **kwargs):
 
     load_legacy_spam_checkers(hs)
     load_legacy_third_party_event_rules(hs)
+    load_legacy_presence_router(hs)
 
     # If we've configured an expiry time for caches, start the background job now.
     setup_expire_lru_cache_entries(hs)

synapse/config/server.py

@@ -248,6 +248,7 @@ def read_config(self, config, **kwargs):
             self.use_presence = config.get("use_presence", True)
 
         # Custom presence router module
+        # This is the legacy way of configuring it (the config should now be put in the modules section)
         self.presence_router_module_class = None
         self.presence_router_config = None
         presence_router_config = presence_config.get("presence_router")
@@ -858,20 +859,6 @@ def generate_config_section(
           #
           #enabled: false
 
-          # Presence routers are third-party modules that can specify additional logic
-          # to where presence updates from users are routed.
-          #
-          presence_router:
-            # The custom module's class. Uncomment to use a custom presence router module.
-            #
-            #module: "my_custom_router.PresenceRouter"
-
-            # Configuration options of the custom module. Refer to your module's
-            # documentation for available options.
-            #
-            #config:
-            #  example_option: 'something'
-
         # Whether to require authentication to retrieve profile data (avatars,
         # display names) of other users through the client API. Defaults to
         # 'false'. Note that profile data is also available via the federation

synapse/events/presence_router.py

@@ -11,45 +11,110 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-
-from typing import TYPE_CHECKING, Dict, Iterable, Set, Union
+from typing import (
+    TYPE_CHECKING,
+    Awaitable,
+    Callable,
+    Dict,
+    Iterable,
+    List,
+    Optional,
+    Set,
+    Union,
+)
 
 from synapse.api.presence import UserPresenceState
+from synapse.util.async_helpers import maybe_awaitable
 
 if TYPE_CHECKING:
     from synapse.server import HomeServer
 
+GET_USERS_FOR_STATES = Callable[
+    [Iterable[UserPresenceState]], Awaitable[Dict[str, Set[UserPresenceState]]]
+]
+GET_INTERESTED_USERS = Callable[[str], Awaitable[Union[Set[str], str]]]
+
+
+def load_legacy_presence_router(hs: "HomeServer"):
+    """Wrapper that loads a presence router module configured using the old
+    configuration, and registers the hooks they implement.
+    """
+
+    if hs.config.presence_router_module_class is None:
+        return
+
+    module = hs.config.presence_router_module_class
+    config = hs.config.presence_router_config
+    api = hs.get_module_api()
+
+    presence_router = module(config=config, module_api=api)
+
+    # The known hooks. If a module implements a method which name appears in this set,
+    # we'll want to register it.
+    presence_router_methods = {
+        "get_users_for_states",
+        "get_interested_users",
+    }
+
+    # All methods that the module provides should be async, but this wasn't enforced
+    # in the old module system, so we wrap them if needed
+    def async_wrapper(f: Optional[Callable]) -> Optional[Callable[..., Awaitable]]:
+        # f might be None if the callback isn't implemented by the module. In this
+        # case we don't want to register a callback at all so we return None.
+        if f is None:
+            return None
+
+        def run(*args, **kwargs):
+            # mypy doesn't do well across function boundaries so we need to tell it
+            # f is definitely not None.
+            assert f is not None
+
+            return maybe_awaitable(f(*args, **kwargs))
+
+        return run
+
+    # Register the hooks through the module API.
+    hooks = {
+        hook: async_wrapper(getattr(presence_router, hook, None))
+        for hook in presence_router_methods
+    }
+
+    api.register_presence_router_callbacks(**hooks)
+
 
 class PresenceRouter:
     """
     A module that the homeserver will call upon to help route user presence updates to
-    additional destinations. If a custom presence router is configured, calls will be
-    passed to that instead.
+    additional destinations.
     """
 
     ALL_USERS = "ALL"
 
     def __init__(self, hs: "HomeServer"):
-        self.custom_presence_router = None
+        # Initially there are no callbacks
+        self._get_users_for_states_callbacks: List[GET_USERS_FOR_STATES] = []
+        self._get_interested_users_callbacks: List[GET_INTERESTED_USERS] = []
 
-        # Check whether a custom presence router module has been configured
-        if hs.config.presence_router_module_class:
-            # Initialise the module
-            self.custom_presence_router = hs.config.presence_router_module_class(
-                config=hs.config.presence_router_config, module_api=hs.get_module_api()
+    def register_presence_router_callbacks(
+        self,
+        get_users_for_states: Optional[GET_USERS_FOR_STATES] = None,
+        get_interested_users: Optional[GET_INTERESTED_USERS] = None,
+    ):
+        # PresenceRouter modules are required to implement both of these methods
+        # or neither of them as they are assumed to act in a complementary manner
+        paired_methods = [get_users_for_states, get_interested_users]
+        if paired_methods.count(None) == 1:
+            raise Exception(
+                "PresenceRouter modules must register neither or both of the paired callbacks: "
+                "[get_users_for_states, get_interested_users]"
             )
 
-            # Ensure the module has implemented the required methods
-            required_methods = ["get_users_for_states", "get_interested_users"]
-            for method_name in required_methods:
-                if not hasattr(self.custom_presence_router, method_name):
-                    raise Exception(
-                        "PresenceRouter module '%s' must implement all required methods: %s"
-                        % (
-                            hs.config.presence_router_module_class.__name__,
-                            ", ".join(required_methods),
-                        )
-                    )
+        # Append the methods provided to the lists of callbacks
+        if get_users_for_states is not None:
+            self._get_users_for_states_callbacks.append(get_users_for_states)
+
+        if get_interested_users is not None:
+            self._get_interested_users_callbacks.append(get_interested_users)
 
     async def get_users_for_states(
         self,
@@ -66,14 +131,33 @@ async def get_users_for_states(
           A dictionary of user_id -> set of UserPresenceState, indicating which
           presence updates each user should receive.
         """
-        if self.custom_presence_router is not None:
-            # Ask the custom module
-            return await self.custom_presence_router.get_users_for_states(
-                state_updates=state_updates
+
+        # Bail out early without if we don't have any callbacks to run.
+        if len(self._get_users_for_states_callbacks) == 0:
+            # Don't include any extra destinations for presence updates
+            return {}
+
+        # If there are multiple callbacks for get_users_for_state then we want to
+        # return ALL of the extra destinations, this method joins two sets of extra
+        # destinations into one
+        def combine(
+            dict1: Dict[str, Set[UserPresenceState]],
+            dict2: Dict[str, Set[UserPresenceState]],
+        ) -> Dict[str, Set[UserPresenceState]]:
+            for key, new_entries in dict2.items():
+                old_entries = dict1.get(key, set())
+                dict1[key] = old_entries.union(new_entries)
+
+            return dict1
+
+        users_for_states = {}
+        # run all the callbacks for get_users_for_states and combine the results
+        for callback in self._get_users_for_states_callbacks:
+            users_for_states = combine(
+                users_for_states, await callback(state_updates=state_updates)
             )
 
-        # Don't include any extra destinations for presence updates
-        return {}
+        return users_for_states
 
     async def get_interested_users(self, user_id: str) -> Union[Set[str], ALL_USERS]:
         """
@@ -92,12 +176,30 @@ async def get_interested_users(self, user_id: str) -> Union[Set[str], ALL_USERS]
             A set of user IDs to return presence updates for, or ALL_USERS to return all
             known updates.
         """
-        if self.custom_presence_router is not None:
+
+        # Bail out early if we don't have any callbacks to run.
+        if len(self._get_interested_users_callbacks) == 0:
+            # Don't report any additional interested users
+            return set()
+
+        # If there are multiple callbacks for get_interested_users then we want to
+        # return ALL of the users, this method joins two sets of users into one
+        def combine(
+            set1: Union[Set[str], str],
+            set2: Union[Set[str], str],
+        ) -> Union[Set[str], str]:
+            # if one of the two sets is ALL_USERS then the union is also ALL_USERS
+            if set1 == PresenceRouter.ALL_USERS or set2 == PresenceRouter.ALL_USERS:
+                return PresenceRouter.ALL_USERS
+            else:
+                return set1.union(set2)
+
+        interested_users = set()
+        # run all the callbacks for get_interested_users and combine the results
+        for callback in self._get_interested_users_callbacks:
             # Ask the custom module for interested users
-            return await self.custom_presence_router.get_interested_users(
-                user_id=user_id
+            interested_users = combine(
+                interested_users, await callback(user_id=user_id)
             )
 
-        # A custom presence router is not defined.
-        # Don't report any additional interested users
-        return set()
+        return interested_users

synapse/module_api/__init__.py

@@ -111,6 +111,7 @@ def __init__(self, hs: "HomeServer", auth_handler):
         self._spam_checker = hs.get_spam_checker()
         self._account_validity_handler = hs.get_account_validity_handler()
         self._third_party_event_rules = hs.get_third_party_event_rules()
+        self._presence_router = hs.get_presence_router()
 
     #################################################################################
     # The following methods should only be called during the module's initialisation.
@@ -130,6 +131,11 @@ def register_third_party_rules_callbacks(self):
         """Registers callbacks for third party event rules capabilities."""
         return self._third_party_event_rules.register_third_party_rules_callbacks
 
+    @property
+    def register_presence_router_callbacks(self):
+        """Registers callbacks for presence router capabilities."""
+        return self._presence_router.register_presence_router_callbacks
+
     def register_web_resource(self, path: str, resource: IResource):
         """Registers a web resource to be served at the given path.