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Merge pull request #2035 from matrix-org/travis/1.0/msc688-msc1227-lazy-loading

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Spec lazy-loading room members
application_service/release-r0.1.1
Travis Ralston 5 years ago committed by GitHub
parent fbdb56a29f 56e1640bea
commit 19f017f9bd
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9 changed files with 238 additions and 91 deletions
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14
api/client-server/definitions/room_event_filter.yaml
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@ -16,6 +16,20 @@ allOf:
- type: object
title: RoomEventFilter
properties:
lazy_load_members:
type: boolean
description: |-
If ``true``, enables lazy-loading of membership events. See
`Lazy-loading room members <#lazy-loading-room-members>`_
for more information. Defaults to ``false``.
include_redundant_members:
type: boolean
description: |-
If ``true``, sends all membership events for all events, even if they have already
been sent to the client. Does not
apply unless ``lazy_load_members`` is ``true``. See
`Lazy-loading room members <#lazy-loading-room-members>`_
for more information. Defaults to ``false``.
not_rooms:
description: A list of room IDs to exclude. If this list is absent then no rooms
are excluded. A matching room will be excluded even if it is listed in the ``'rooms'``

29
api/client-server/definitions/sync_filter.yaml
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@ -47,7 +47,7 @@ properties:
not_rooms:
description: A list of room IDs to exclude. If this list is absent then no rooms
are excluded. A matching room will be excluded even if it is listed in the ``'rooms'``
filter. This filter is applied before the filters in ``ephemeral``,
filter. This filter is applied before the filters in ``ephemeral``,
``state``, ``timeline`` or ``account_data``
items:
type: string
@ -73,33 +73,6 @@ properties:
allOf:
- $ref: room_event_filter.yaml
description: The state events to include for rooms.
properties:
lazy_load_members:
type: boolean
description: |-
If ``true``, the only ``m.room.member`` events returned in
the ``state`` section of the ``/sync`` response are those
which are definitely necessary for a client to display
the ``sender`` of the timeline events in that response.
If ``false``, ``m.room.member`` events are not filtered.
By default, servers should suppress duplicate redundant
lazy-loaded ``m.room.member`` events from being sent to a given
client across multiple calls to ``/sync``, given that most clients
cache membership events (see ``include_redundant_members``
to change this behaviour).
include_redundant_members:
type: boolean
description: |-
If ``true``, the ``state`` section of the ``/sync`` response will
always contain the ``m.room.member`` events required to display
the ``sender`` of the timeline events in that response, assuming
``lazy_load_members`` is enabled. This means that redundant
duplicate member events may be returned across multiple calls to
``/sync``. This is useful for naive clients who never track
membership data. If ``false``, duplicate ``m.room.member`` events
may be suppressed by the server across multiple calls to ``/sync``.
If ``lazy_load_members`` is ``false`` this field is ignored.
timeline:
allOf:
- $ref: room_event_filter.yaml

3
api/client-server/event_context.yaml
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@ -34,6 +34,9 @@ paths:
This API returns a number of events that happened just before and
after the specified event. This allows clients to get the context
surrounding an event.
*Note*: This endpoint supports lazy-loading of room member events. See `Filtering <#lazy-loading-room-members>`_
for more information.
operationId: getEventContext
security:
- accessToken: []

18
api/client-server/message_pagination.yaml
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@ -33,6 +33,9 @@ paths:
description: |-
This API returns a list of message and state events for a room. It uses
pagination query parameters to paginate history in the room.
*Note*: This endpoint supports lazy-loading of room member events. See `Filtering <#lazy-loading-room-members>`_
for more information.
operationId: getRoomEvents
security:
- accessToken: []
@ -111,6 +114,21 @@ paths:
type: object
title: RoomEvent
"$ref": "definitions/event-schemas/schema/core-event-schema/room_event.yaml"
state:
type: array
description: |-
A list of state events relevant to showing the ``chunk``. For example, if
``lazy_load_members`` is enabled in the filter then this may contain
the membership events for the senders of events in the ``chunk``.
Unless ``include_redundant_members`` is ``true``, the server
may remove membership events which would have already been
sent to the client in prior calls to this endpoint, assuming
the membership of those members has not changed.
items:
type: object
title: RoomStateEvent
$ref: "definitions/event-schemas/schema/core-event-schema/state_event.yaml"
examples:
application/json: {
"start": "t47429-4392820_219380_26003_2265",

38
api/client-server/rooms.yaml
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@ -184,6 +184,44 @@ paths:
description: The room to get the member events for.
required: true
x-example: "!636q39766251:example.com"
- in: query
name: at
type: string
description: |-
The point in time (pagination token) to return members for in the room.
This token can be obtained from a ``prev_batch`` token returned for
each room by the sync API. Defaults to the current state of the room,
as determined by the server.
x-example: "YWxsCgpOb25lLDM1ODcwOA"
# XXX: As mentioned in MSC1227, replacing `[not_]membership` with a JSON
# filter might be a better alternative.
# See https://github.com/matrix-org/matrix-doc/issues/1337
- in: query
name: membership
type: string
enum:
- join
- invite
- leave
- ban
description: |-
The kind of membership to filter for. Defaults to no filtering if
unspecified. When specified alongside ``not_membership``, the two
parameters create an 'or' condition: either the membership *is*
the same as ``membership`` **or** *is not* the same as ``not_membership``.
x-example: "join"
- in: query
name: not_membership
type: string
enum:
- join
- invite
- leave
- ban
description: |-
The kind of membership to exclude from the results. Defaults to no
filtering if unspecified.
x-example: leave
security:
- accessToken: []
responses:

68
api/client-server/sync.yaml
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@ -34,6 +34,20 @@ paths:
Clients use this API when they first log in to get an initial snapshot
of the state on the server, and then continue to call this API to get
incremental deltas to the state, and to receive new messages.
*Note*: This endpoint supports lazy-loading. See `Filtering <#filtering>`_
for more information. Lazy-loading members is only supported on a ``StateFilter``
for this endpoint. When lazy-loading is enabled, servers MUST include the
syncing user's own membership event when they join a room, or when the
full state of rooms is requested, to aid discovering the user's avatar &
displayname.
Like other members, the user's own membership event is eligible
for being considered redundant by the server. When a sync is ``limited``,
the server MUST return membership events for events in the gap
(between ``since`` and the start of the returned timeline), regardless
as to whether or not they are redundant. This ensures that joins/leaves
and profile changes which occur during the gap are not lost.
operationId: sync
security:
- accessToken: []
@ -49,6 +63,8 @@ paths:
requests. Creating a filter using the filter API is recommended for
clients that reuse the same filter multiple times, for example in
long poll requests.
See `Filtering <#filtering>`_ for more information.
x-example: "66696p746572"
- in: query
name: since
@ -125,6 +141,50 @@ paths:
title: Joined Room
type: object
properties:
summary:
title: RoomSummary
type: object
description: |-
Information about the room which clients may need to
correctly render it to users.
properties:
"m.heroes":
type: array
description: |-
The users which can be used to generate a room name
if the room does not have one. Required if the room's
``m.room.name`` or ``m.room.canonical_alias`` state events
are unset or empty.
This should be the first 5 members of the room, ordered
by stream ordering, which are joined or invited. The
list must never include the client's own user ID. When
no joined or invited members are available, this should
consist of the banned and left users. More than 5 members
may be provided, however less than 5 should only be provided
when there are less than 5 members to represent.
When lazy-loading room members is enabled, the membership
events for the heroes MUST be included in the ``state``,
unless they are redundant. When the list of users changes,
the server notifies the client by sending a fresh list of
heroes. If there are no changes since the last sync, this
field may be omitted.
items:
type: string
"m.joined_member_count":
type: integer
description: |-
The number of users with ``membership`` of ``join``,
including the client's own user ID. If this field has
not changed since the last sync, it may be omitted.
Required otherwise.
"m.invited_member_count":
type: integer
description: |-
The number of users with ``membership`` of ``invite``.
If this field has not changed since the last sync, it
may be omitted. Required otherwise.
state:
title: State
type: object
@ -305,6 +365,14 @@ paths:
"rooms": {
"join": {
"!726s6s6q:example.com": {
"summary": {
"m.heroes": [
"@alice:example.com",
"@bob:example.com"
],
"m.joined_member_count": 2,
"m.invited_member_count": 0
},
"state": {
"events": [
{

1
changelogs/client_server/newsfragments/2035.feature
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@ -0,0 +1 @@
Add the option to lazy-load room members for increased client performance.

60
specification/client_server_api.rst
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@ -1317,6 +1317,66 @@ Filters can be created on the server and can be passed as as a parameter to APIs
which return events. These filters alter the data returned from those APIs.
Not all APIs accept filters.
Lazy-loading room members
~~~~~~~~~~~~~~~~~~~~~~~~~
Membership events often take significant resources for clients to track. In an
effort to reduce the number of resources used, clients can enable "lazy-loading"
for room members. By doing this, servers will attempt to only send membership events
which are relevant to the client.
It is important to understand that lazy-loading is not intended to be a
perfect optimisation, and that it may not be practical for the server to
calculate precisely which membership events are relevant to the client. As a
result, it is valid for the server to send redundant membership events to the
client to ease implementation, although such redundancy should be minimised
where possible to conserve bandwidth.
In terms of filters, lazy-loading is enabled by enabling ``lazy_load_members``
on a ``RoomEventFilter`` (or a ``StateFilter`` in the case of ``/sync`` only).
When enabled, lazy-loading aware endpoints (see below) will only include
membership events for the ``sender`` of events being included in the response.
For example, if a client makes a ``/sync`` request with lazy-loading enabled,
the server will only return membership events for the ``sender`` of events in
the timeline, not all members of a room.
When processing a sequence of events (e.g. by looping on ``/sync`` or
paginating ``/messages``), it is common for blocks of events in the sequence
to share a similar set of senders. Rather than responses in the sequence
sending duplicate membership events for these senders to the client, the
server MAY assume that clients will remember membership events they have
already been sent, and choose to skip sending membership events for members
whose membership has not changed. These are called 'redundant membership
events'. Clients may request that redundant membership events are always
included in responses by setting ``include_redundant_members`` to true in the
filter.
The expected pattern for using lazy-loading is currently:
* Client performs an initial /sync with lazy-loading enabled, and receives
only the membership events which relate to the senders of the events it
receives.
* Clients which support display-name tab-completion or other operations which
require rapid access to all members in a room should call /members for the
currently selected room, with an ``?at`` parameter set to the /sync
response's from token. The member list for the room is then maintained by
the state in subsequent incremental /sync responses.
* Clients which do not support tab-completion may instead pull in profiles for
arbitrary users (e.g. read receipts, typing notifications) on demand by
querying the room state or ``/profile``.
.. TODO-spec
This implies that GET /state should also take an ``?at`` param
The current endpoints which support lazy-loading room members are:
* |/sync|_
* |/rooms/<room_id>/messages|_
* |/rooms/{roomId}/context/{eventId}|_
API endpoints
~~~~~~~~~~~~~
{{filter_cs_http_api}}
Events

98
specification/modules/instant_messaging.rst
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@ -278,70 +278,42 @@ choose a name:
#. If the room has an `m.room.canonical_alias`_ state event with a non-empty
``alias`` field, use the alias given by that field as the name.
#. If neither of the above conditions are met, a name should be composed based
on the members of the room. Clients should consider `m.room.member`_ events
for users other than the logged-in user, with ``membership: join`` or
``membership: invite``.
.. _active_members:
i. If there is only one such event, the display name for the room should be
the `disambiguated display name`_ of the corresponding user.
#. If there are two such events, they should be lexicographically sorted by
their ``state_key`` (i.e. the corresponding user IDs), and the display
name for the room should be the `disambiguated display name`_ of both
users: "<user1> and <user2>", or a localised variant thereof.
#. If there are three or more such events, the display name for the room
should be based on the disambiguated display name of the user
corresponding to the first such event, under a lexicographical sorting
according to their ``state_key``. The display name should be in the
format "<user1> and <N> others" (or a localised variant thereof), where N
is the number of `m.room.member`_ events with ``membership: join`` or
``membership: invite``, excluding the logged-in user and "user1".
For example, if Alice joins a room, where Bob (whose user id is
``@superuser:example.com``), Carol (user id ``@carol:example.com``) and
Dan (user id ``@dan:matrix.org``) are in conversation, Alice's
client should show the room name as "Carol and 2 others".
.. TODO-spec
Sorting by user_id certainly isn't ideal, as IDs at the start of the
alphabet will end up dominating room names: they will all be called
"Arathorn and 15 others". Furthermore - user_ids are not necessarily
ASCII, which means we need to either specify a collation order, or specify
how to choose one.
Ideally we might sort by the time when the user was first invited to, or
first joined the room. But we don't have this information.
See https://matrix.org/jira/browse/SPEC-267 for further discussion.
#. If the room has no valid ``m.room.name`` or ``m.room.canonical_alias``
event, and no active members other than the current user, clients should
consider ``m.room.member`` events with ``membership: leave``. If such events
exist, a display name such as "Empty room (was <user1> and <N> others)" (or
a localised variant thereof) should be used, following similar rules as for
active members (see `above <active_members_>`_).
#. A complete absence of room name, canonical alias, and room members is likely
to indicate a problem with creating the room or synchronising the state
table; however clients should still handle this situation. A display name
such as "Empty room" (or a localised variant thereof) should be used in this
situation.
.. _`disambiguated display name`: `Calculating the display name for a user`_
Clients SHOULD NOT use `m.room.aliases`_ events as a source for room names, as
it is difficult for clients to agree on the best alias to use, and aliases can
change unexpectedly.
.. TODO-spec
How can we make this less painful for clients to implement, without forcing
an English-language implementation on them all? See
https://matrix.org/jira/browse/SPEC-425.
#. If neither of the above conditions are met, the client can optionally guess
an alias from the ``m.room.alias`` events in the room. This is a temporary
measure while clients do not promote canonical aliases as prominently. This
step may be removed in a future version of the specification.
#. If none of the above conditions are met, a name should be composed based
on the members of the room. Clients should consider `m.room.member`_ events
for users other than the logged-in user, as defined below.
i. If the number of ``m.heroes`` for the room are greater or equal to
``m.joined_member_count + m.invited_member_count - 1``, then use the
membership events for the heroes to calculate display names for the
users (`disambiguating them if required`_) and concatenating them. For
example, the client may choose to show "Alice, Bob, and Charlie
(@charlie:example.org)" as the room name. The client may optionally
limit the number of users it uses to generate a room name.
#. If there are fewer heroes than ``m.joined_member_count + m.invited_member_count
- 1``, and ``m.joined_member_count + m.invited_member_count`` is greater
than 1, the client should use the heroes to calculate display names for
the users (`disambiguating them if required`_) and concatenating them
alongside a count of the remaining users. For example, "Alice, Bob, and
1234 others".
#. If ``m.joined_member_count + m.invited_member_count`` is less than or
equal to 1 (indicating the member is alone), the client should use the
rules above to indicate that the room was empty. For example, "Empty
Room (was Alice)", "Empty Room (was Alice and 1234 others)", or
"Empty Room" if there are no heroes.
Clients SHOULD internationalise the room name to the user's language when using
the ``m.heroes`` to calculate the name. Clients SHOULD use minimum 5 heroes to
calculate room names where possible, but may use more or less to fit better with
their user experience.
.. _`disambiguating them if required`: `Calculating the display name for a user`_
Forming relationships between events
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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