[Buildbot-commits] [Buildbot] #2652: [nine] Coordinate Messages and Data

[Buildbot trac]

#2652: [nine] Coordinate Messages and Data
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Reporter:  dustin  |      Owner:
    Type:  task    |     Status:  new
Priority:  major   |  Milestone:  0.9.0
 Version:          |   Keywords:
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 We currently have a DB API which may use a backend DB without read-after-
 write consistency, due to replication delay.
 And we have an MQ API which introduces an unbounded propagation delay in
 messages.

 So it's possible to receive a message about a change, say a build
 finishing, after which a DB query still shows the build as unfinished.
 Likewise, it's possible to see an updated value from a DB query long
 before the corresponding message arrives.

 This causes problems.
 For example, a user might want an event for every build triggered for a
 particular buildset.
 The naive approach is to get the list of current builds for that buildset,
 and subscribe to builds with that buildset in the future.
 Given the timing discrepancies, though, this approach may either miss
 builds for which a message has already been sent but which is not in the
 DB yet; or double-report a build which is already in the DB but for which
 the message has not yet been delivered.

 I don't have any good solutions to this.

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Ticket URL: <http://trac.buildbot.net/ticket/2652>
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