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c4240cc1Sam Whited design: add an open question to stanza mux 1 year, 11 months ago

#Proposal: Implement stanza handlers

Author(s): Sam Whited Last updated: 2020-02-17 Status: accepted Discussion: https://mellium.im/issue/25


An API is needed for multiplexing based on stanzas that allows for matching based on type and quickly replying or re-marshaling the original stanzas.


In the previous IQ mux proposal a new mechanism for routing IQ stanzas based on their type and payload was introduced. In practice, registering the IQ muxer ended up being cumbersome, and the previous proposal did not solve the problem of routing message or presence stanzas (this was deliberately left for a future proposal). To solve both of these problems at once the current multiplexer can be adapted using what we learned from the IQ mux experiment such that it can route message and presence stanzas based on their type, and IQs based on their type and payload.


  • Ability to multiplex IQ stanzas by stanza type and payload name
  • Ability to multiplex message and presence stanzas by type
  • IQ, message, presence, and other general top level elements must have their own distinct handler types
  • The handlers must be extensible to add functionality such as replying to IQs or other thought of features in the future without making breaking API changes to the handler itself


In addition to the existing Handler and IQHandler types, the following types would be added for messages and presence:

type MessageHandler interface {
        HandleMessage(msg stanza.Message, t xmlstream.TokenReadEncoder) error
    MessageHandler responds to message stanzas.

type PresenceHandler interface {
        HandlePresence(p stanza.Presence, t xmlstream.TokenReadEncoder) error
    PresenceHandler responds to presence stanzas.

Adapters for functions with the provided signature would also be made available, similar to HandlerFunc.

The existing IQ mux would be removed (this is a backwards incompatible change, however, we are pre-1.0 and the IQ mux was never put into a release) and its methods and functionality would be added to ServeMux.

The options related to registering stanzas would then be modified to take the new patterns as follows:

func IQ(typ stanza.IQType, payload xml.Name, h IQHandler) Option
    IQ returns an option that matches IQ stanzas based on their type and the
    name of the payload.

func Message(typ stanza.MessageType, h MessageHandler) Option
    Message returns an option that matches message stanzas by type.

func Presence(typ stanza.PresenceType, h PresenceHandler) Option
    Presence returns an option that matches presence stanzas by type.

Functional versions of these options (taking a HandlerFunc) would also be added.

#Open Questions

  • What happens if the normal Handle options are used to register a handler that would match stanzas?
  • We still need some way to match on Message/Presence payloads, otherwise how do we have different handlers for eg. IBB data payloads or messages with a body.