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

.. Copyright 2019 The Matrix.org Foundation C.I.C.
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Server Notices
==============

.. _module:server-notices:

Homeserver hosts often want to send messages to users in an official capacity,
or have resource limits which affect a user's ability to use the homeserver.
For example, the homeserver may be limited to a certain number of active users
per month and has exceeded that limit. To communicate this failure to users,
the homeserver would use the Server Notices room.

The aesthetics of the room (name, topic, avatar, etc) are left as an implementation
detail. It is recommended that the homeserver decorate the room such that it looks
like an official room to users.

Events
------
Notices are sent to the client as normal ``m.room.message`` events with a
``msgtype`` of ``m.server_notice`` in the server notices room. Events with
a ``m.server_notice`` ``msgtype`` outside of the server notice room must
be ignored by clients.

The specified values for ``server_notice_type`` are:

:``m.server_notice.usage_limit_reached``:
  The server has exceeded some limit which requires the server administrator
  to intervene. The ``limit_type`` describes the kind of limit reached.
  The specified values for ``limit_type`` are:

  :``monthly_active_user``:
    The server's number of active users in the last 30 days has exceeded the
    maximum. New connections are being refused by the server. What defines
    "active" is left as an implementation detail, however servers are encouraged
    to treat syncing users as "active".


{{m_room_message_m_server_notice_event}}

Client behaviour
----------------
Clients can identify the server notices room by the ``m.server_notice`` tag
on the room. Active notices are represented by the `pinned events <#m-room-pinned-events>`_
in the server notices room. Server notice events pinned in that room should
be shown to the user through special UI and not through the normal pinned
events interface in the client. For example, clients may show warning banners
or bring up dialogs to get the user's attention. Events which are not server
notice events and are pinned in the server notices room should be shown just
like any other pinned event in a room.

The client must not expect to be able to reject an invite to join the server
notices room. Attempting to reject the invite must result in a
``M_CANNOT_LEAVE_SERVER_NOTICE_ROOM`` error. Servers should not prevent the user
leaving the room after joining the server notices room, however the same error
code must be used if the server will prevent leaving the room.

Server behaviour
----------------
Servers should manage exactly 1 server notices room per user. Servers must
identify this room to clients with the ``m.server_notice`` tag. Servers should
invite the target user rather than automatically join them to the server notice
room.

How servers send notices to clients, and which user they use to send the events,
is left as an implementation detail for the server.