mirror of
https://mau.dev/maunium/synapse.git
synced 2024-11-18 07:52:56 +01:00
113 lines
4.7 KiB
ReStructuredText
113 lines
4.7 KiB
ReStructuredText
==================
|
|
Room Join Workflow
|
|
==================
|
|
|
|
An outline of the workflows required when a user joins a room.
|
|
|
|
Discovery
|
|
=========
|
|
|
|
To join a room, a user has to discover the room by some mechanism in order to
|
|
obtain the (opaque) Room ID and a candidate list of likely home servers that
|
|
contain it.
|
|
|
|
Sending an Invitation
|
|
---------------------
|
|
|
|
The most direct way a user discovers the existence of a room is from a
|
|
invitation from some other user who is a member of that room.
|
|
|
|
The inviter's HS sets the membership status of the invitee to "invited" in the
|
|
"m.members" state key by sending a state update PDU. The HS then broadcasts this
|
|
PDU among the existing members in the usual way. An invitation message is also
|
|
sent to the invited user, containing the Room ID and the PDU ID of this
|
|
invitation state change and potentially a list of some other home servers to use
|
|
to accept the invite. The user's client can then choose to display it in some
|
|
way to alert the user.
|
|
|
|
[[TODO(paul): At present, no API has been designed or described to actually send
|
|
that invite to the invited user. Likely it will be some facet of the larger
|
|
user-user API required for presence, profile management, etc...]]
|
|
|
|
Directory Service
|
|
-----------------
|
|
|
|
Alternatively, the user may discover the channel via a directory service; either
|
|
by performing a name lookup, or some kind of browse or search acitivty. However
|
|
this is performed, the end result is that the user's home server requests the
|
|
Room ID and candidate list from the directory service.
|
|
|
|
[[TODO(paul): At present, no API has been designed or described for this
|
|
directory service]]
|
|
|
|
|
|
Joining
|
|
=======
|
|
|
|
Once the ID and home servers are obtained, the user can then actually join the
|
|
room.
|
|
|
|
Accepting an Invite
|
|
-------------------
|
|
|
|
If a user has received and accepted an invitation to join a room, the invitee's
|
|
home server can now send an invite acceptance message to a chosen candidate
|
|
server from the list given in the invitation, citing also the PDU ID of the
|
|
invitation as "proof" of their invite. (This is required as due to late message
|
|
propagation it could be the case that the acceptance is received before the
|
|
invite by some servers). If this message is allowed by the candidate server, it
|
|
generates a new PDU that updates the invitee's membership status to "joined",
|
|
referring back to the acceptance PDU, and broadcasts that as a state change in
|
|
the usual way. The newly-invited user is now a full member of the room, and
|
|
state propagation proceeds as usual.
|
|
|
|
Joining a Public Room
|
|
---------------------
|
|
|
|
If a user has discovered the existence of a room they wish to join but does not
|
|
have an active invitation, they can request to join it directly by sending a
|
|
join message to a candidate server on the list provided by the directory
|
|
service. As this list may be out of date, the HS should be prepared to retry
|
|
other candidates if the chosen one is no longer aware of the room, because it
|
|
has no users as members in it.
|
|
|
|
Once a candidate server that is aware of the room has been found, it can
|
|
broadcast an update PDU to add the member into the "m.members" key setting their
|
|
state directly to "joined" (i.e. bypassing the two-phase invite semantics),
|
|
remembering to include the new user's HS in that list.
|
|
|
|
Knocking on a Semi-Public Room
|
|
------------------------------
|
|
|
|
If a user requests to join a room but the join mode of the room is "knock", the
|
|
join is not immediately allowed. Instead, if the user wishes to proceed, they
|
|
can instead post a "knock" message, which informs other members of the room that
|
|
the would-be joiner wishes to become a member and sets their membership value to
|
|
"knocked". If any of them wish to accept this, they can then send an invitation
|
|
in the usual way described above. Knowing that the user has already knocked and
|
|
expressed an interest in joining, the invited user's home server should
|
|
immediately accept that invitation on the user's behalf, and go on to join the
|
|
room in the usual way.
|
|
|
|
[[NOTE(Erik): Though this may confuse users who expect 'X has joined' to
|
|
actually be a user initiated action, i.e. they may expect that 'X' is actually
|
|
looking at synapse right now?]]
|
|
|
|
[[NOTE(paul): Yes, a fair point maybe we should suggest HSes don't do that, and
|
|
just offer an invite to the user as normal]]
|
|
|
|
Private and Non-Existent Rooms
|
|
------------------------------
|
|
|
|
If a user requests to join a room but the room is either unknown by the home
|
|
server receiving the request, or is known by the join mode is "invite" and the
|
|
user has not been invited, the server must respond that the room does not exist.
|
|
This is to prevent leaking information about the existence and identity of
|
|
private rooms.
|
|
|
|
|
|
Outstanding Questions
|
|
=====================
|
|
|
|
* Do invitations or knocks time out and expire at some point? If so when? Time
|
|
is hard in distributed systems.
|