Bug 21093

Summary: Approver: AddDispatchOperation assumes CDO.Channels is immutable
Product: Telepathy Reporter: Simon McVittie <smcv>
Component: tp-specAssignee: Simon McVittie <smcv>
Status: RESOLVED FIXED QA Contact: Telepathy bugs list <telepathy-bugs>
Severity: normal    
Priority: medium Keywords: patch
Version: unspecified   
Hardware: Other   
OS: All   
URL: http://git.collabora.co.uk/?p=user/smcv/telepathy-spec-smcv.git;a=shortlog;h=refs/heads/approver-abibreak
i915 platform: i915 features:
Bug Depends on:    
Bug Blocks: 21148, 21174    

Description Simon McVittie 2009-04-07 12:58:56 UTC
The Channels property on ChannelDispatchOperation objects is mutable (channels can fall off). However, AddDispatchOperation documentation implies that it is immutable.

We should separate the Channels into a separate argument, and document the inherent race conditions. For reference, those races are:

* channels that close immediately after AddDispatchOperation go bad - the approver should call a method on the channel (i.e. make a TpChannel) to notice whether they're dead or not

* channels that close immediately after HandleChannels is called - the handler should do the same
Comment 1 Simon McVittie 2009-04-10 10:53:33 UTC
Discussion with Rob resulted in this proposal:

* CDOs' Channels property remains mutable
* CDOs aren't allowed to emit ChannelLost or Finished until all approvers have returned from AddDispatchOperation (they should queue up the signals for later sending if necessary)
* As a result, Approvers 
* Non-Approvers that are somehow given a CDO's object path (i.e. mostly Observers) are required to connect to ChannelLost, connect to Finished and GetAll(), as per the usual connect-signals-before-state-recovery doctrine

I'll spec it up on Monday.
Comment 2 Will Thompson 2009-04-11 02:29:14 UTC
(In reply to comment #1)
> * As a result, Approvers 

This sentence doesn't seem to
Comment 3 Simon McVittie 2009-04-13 07:45:05 UTC
Should have been:

* As a result, Approvers may assume that Channels stays constant at least until they return from ADO, so they have time to connect to ChannelLost
Comment 5 Simon McVittie 2009-04-13 10:14:56 UTC
Yes (specmeet)
Comment 6 Simon McVittie 2009-04-14 07:59:55 UTC
Fixed in git, will be in 0.17.23, MC needs to catch up (Bug #21174)

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