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113 lines
4.4 KiB
ReStructuredText
Presence
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========
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.. _module:presence:
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Each user has the concept of presence information. This encodes:
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* Whether the user is currently online
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* How recently the user was last active (as seen by the server)
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* Whether a given client considers the user to be currently idle
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* Arbitrary information about the user's current status (e.g. "in a meeting").
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This information is collated from both per-device (``online``, ``idle``,
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``last_active``) and per-user (status) data, aggregated by the user's homeserver
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and transmitted as an ``m.presence`` event. This is one of the few events which
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are sent *outside the context of a room*. Presence events are sent to all users
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who subscribe to this user's presence through a presence list or by sharing
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membership of a room.
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A presence list is a list of user IDs whose presence the user wants to follow.
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To be added to this list, the user being added must be invited by the list owner
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who must accept the invitation.
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User's presence state is represented by the ``presence`` key, which is an enum
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of one of the following:
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- ``online`` : The default state when the user is connected to an event
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stream.
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- ``unavailable`` : The user is not reachable at this time e.g. they are
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idle.
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- ``offline`` : The user is not connected to an event stream or is
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explicitly suppressing their profile information from being sent.
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- ``free_for_chat`` : The user is generally willing to receive messages
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moreso than default.
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Events
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------
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{{presence_events}}
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Client behaviour
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----------------
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Clients can manually set/get their presence/presence list using the HTTP APIs
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listed below.
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{{presence_http_api}}
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Idle timeout
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~~~~~~~~~~~~
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Clients SHOULD implement an "idle timeout". This is a timer which fires after
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a period of inactivity on the client. The definition of inactivity varies
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depending on the client. For example, web implementations may determine
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inactivity to be not moving the mouse for a certain period of time. When this
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timer fires it should set the presence state to ``unavailable``. When the user
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becomes active again (e.g. by moving the mouse) the client should set the
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presence state to ``online``. A timeout value between 1 and 5 minutes is
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recommended.
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Server behaviour
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----------------
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Each user's homeserver stores a "presence list" per user. Once a user accepts
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a presence list, both user's HSes must track the subscription.
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Propagating profile information
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Because the profile display name and avatar information are likely to be used in
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many places of a client's display, changes to these fields SHOULD cause an
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automatic propagation event to occur, informing likely-interested parties of the
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new values. One of these change mechanisms SHOULD be via ``m.presence`` events.
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These events should set ``displayname`` and ``avatar_url`` to the new values
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along with the presence-specific keys. This SHOULD be done automatically by the
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homeserver when a user successfully changes their display name or avatar URL.
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.. admonition:: Rationale
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The intention for sending this information in ``m.presence`` is so that any
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"user list" can display the *current* name/presence for a user ID outside the
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scope of a room e.g. for a user page. This is bundled into a single event for
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several reasons. The user's display name can change per room. This
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event provides the "canonical" name for the user. In addition, the name is
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bundled into a single event for the ease of client implementations. If this
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was not done, the client would need to search all rooms for their own
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membership event to pull out the display name.
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Last active ago
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~~~~~~~~~~~~~~~
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The server maintains a timestamp of the last time it saw a
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pro-active event from the user. A pro-active event may be sending a message to a
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room or changing presence state to a higher level of availability. Levels of
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availability are defined from low to high as follows:
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- ``offline``
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- ``unavailable``
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- ``online``
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- ``free_for_chat``
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Based on this list, changing state from ``unavailable`` to ``online`` counts as
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a pro-active event, whereas ``online`` to ``unavailable`` does not. This
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timestamp is presented via a key called ``last_active_ago`` which gives the
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relative number of milliseconds since the pro-active event.
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Security considerations
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-----------------------
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Presence information is shared with all users who share a room with the target
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user. In large public rooms this could be undesirable.
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