Simplified the protocol to use a master-slave approach; modified terminology.
First draft.
Multi-User Chat (XEP-0045)
This specification addresses the following requirements:
The basic approach to distribution of MUC rooms is as follows:
The room IDs of source rooms SHOULD be opaque to users and unique across all possible peerhosts, for example by generating a UUID in accordance with RFC 4122
This document adds the following terms to those defined in XEP-0045:
In this document, the examples use the following entities.
When the original room owner creates the room (or subsequently configures the room), the service MAY offer the option of making the room a "distributed room". This is done by including the "muc#roomconfig_distributed" feature in the room configuration form:
The room owner specifies a value of "1" or "true"
Alternatively, the firsthost can choose to perform room distribution in the background, rather than exposing the 'muc#roomconfig_distributed' option to the user.
When a firsthost would like a peerhost to provide a shadow, it sends a replication request to the peerhost.
If the peerhost is willing and able to replicate the room, it returns an IQ-result:
Several error cases are possible (the peerhost is resource constrained, the firsthost is forbidden to peer with the peerhost, etc.); these will be specified more fully in a future version of this specification.
Once the peerhost acknowledges that it is willing and able to replicate the room, four things happen:
The new shadow SHOULD request the room history. This is done by sending an IQ-get from the shadow to the source, containing a <history/> element qualified by the 'http://jabber.org/protocol/muc' namespace (the syntax and semantics of this element are described in XEP-0045).
The history request MAY include any of the attributes specified in XEP-0045:: 'maxchars', 'maxstanzas', 'seconds', and 'since'.
The firsthost also informs other connected peerhosts about the new peerhost.
When a user attempts to join a source room, the firsthost determines if it will invite the user to join a shadow at a peerhost instead. The process for determining when to send invitations is implementation specific and might be subject to configuration at the firsthost (e.g., the firsthost might send invitations only to users of a domain associated with the peerhost and only after a certain number of such users have joined the room at the firsthost).
To begin, a user at the peerhost attempts to join the source room at the firsthost:
The source room returns a <redirect/> presence error to the user and invites the user to join a shadow room instead.
Then the source invites the user to the shadow using the protocol defined in Direct MUC Invitations (XEP-0249)
The user then joins the shadow.
The shadow then informs the source (and any other shadows) of the user's presence; it does so by sending presence from the roomjid of the user at the shadow to a roomjid with the same roomnick at the source and shadow(s).
The source then delivers that presence stanza to its local users. (Note: The shadow needs to send only one presence stanza to the source, thus reducing the number of stanzas sent over the server-to-server link between the peerhost and the firsthost.)
When a user sends a message to an instance, the instance sends the message to its local occupants and to other instances.
The source then delivers that message stanza to its local users. (Note: The shadow needs to send only one message stanza to the source, thus reducing the number of stanzas sent over the server-to-server link between the peerhost and the firsthost.)
To follow.
If a MUC service supports distributed rooms, it MUST return a feature of "urn:xmpp:dmuc:0" in response to Service Discovery (XEP-0030)
To follow.
This document requires no interaction with the Internet Assigned Numbers Authority (IANA)
This document requires no interaction with the XMPP Registrar
Thanks to Jay Carlson, Boyd Fletcher, and Michael Krutsch for their early conversations regarding distributed chatrooms.
To follow.