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Document Synapse's behaviour when multiple modules register the same callback/web resource/etc. Co-authored-by: reivilibre <oliverw@matrix.org>
100 lines
3.8 KiB
Markdown
100 lines
3.8 KiB
Markdown
# Presence router callbacks
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Presence router callbacks allow module developers to specify additional users (local or remote)
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to receive certain presence updates from local users. Presence router callbacks can be
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registered using the module API's `register_presence_router_callbacks` method.
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## Callbacks
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The available presence router callbacks are:
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### `get_users_for_states`
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```python
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async def get_users_for_states(
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state_updates: Iterable["synapse.api.UserPresenceState"],
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) -> Dict[str, Set["synapse.api.UserPresenceState"]]
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```
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**Requires** `get_interested_users` to also be registered
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Called when processing updates to the presence state of one or more users. This callback can
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be used to instruct the server to forward that presence state to specific users. The module
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must return a dictionary that maps from Matrix user IDs (which can be local or remote) to the
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`UserPresenceState` changes that they should be forwarded.
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Synapse will then attempt to send the specified presence updates to each user when possible.
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If multiple modules implement this callback, Synapse merges all the dictionaries returned
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by the callbacks. If multiple callbacks return a dictionary containing the same key,
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Synapse concatenates the sets associated with this key from each dictionary.
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### `get_interested_users`
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```python
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async def get_interested_users(
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user_id: str
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) -> Union[Set[str], "synapse.module_api.PRESENCE_ALL_USERS"]
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```
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**Requires** `get_users_for_states` to also be registered
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Called when determining which users someone should be able to see the presence state of. This
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callback should return complementary results to `get_users_for_state` or the presence information
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may not be properly forwarded.
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The callback is given the Matrix user ID for a local user that is requesting presence data and
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should return the Matrix user IDs of the users whose presence state they are allowed to
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query. The returned users can be local or remote.
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Alternatively the callback can return `synapse.module_api.PRESENCE_ALL_USERS`
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to indicate that the user should receive updates from all known users.
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If multiple modules implement this callback, they will be considered in order. Synapse
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calls each callback one by one, and use a concatenation of all the `set`s returned by the
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callbacks. If one callback returns `synapse.module_api.PRESENCE_ALL_USERS`, Synapse uses
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this value instead. If this happens, Synapse does not call any of the subsequent
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implementations of this callback.
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## Example
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The example below is a module that implements both presence router callbacks, and ensures
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that `@alice:example.org` receives all presence updates from `@bob:example.com` and
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`@charlie:somewhere.org`, regardless of whether Alice shares a room with any of them.
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```python
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from typing import Dict, Iterable, Set, Union
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from synapse.module_api import ModuleApi
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class CustomPresenceRouter:
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def __init__(self, config: dict, api: ModuleApi):
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self.api = api
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self.api.register_presence_router_callbacks(
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get_users_for_states=self.get_users_for_states,
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get_interested_users=self.get_interested_users,
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)
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async def get_users_for_states(
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self,
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state_updates: Iterable["synapse.api.UserPresenceState"],
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) -> Dict[str, Set["synapse.api.UserPresenceState"]]:
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res = {}
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for update in state_updates:
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if (
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update.user_id == "@bob:example.com"
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or update.user_id == "@charlie:somewhere.org"
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):
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res.setdefault("@alice:example.com", set()).add(update)
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return res
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async def get_interested_users(
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self,
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user_id: str,
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) -> Union[Set[str], "synapse.module_api.PRESENCE_ALL_USERS"]:
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if user_id == "@alice:example.com":
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return {"@bob:example.com", "@charlie:somewhere.org"}
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return set()
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```
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