[Buildbot-devel] About consistency in mysql cluster

[Dustin J. Mitchell]

I talked about it at my PyBug presentation last year:
  http://people.v.igoro.us/~dustin/buildbot-media/pybug2013/#/13
with speaker notes embedded:
  https://github.com/buildbot/buildbot-media/blob/master/pybug2013/index.html

Dustin

On Wed, Jul 9, 2014 at 9:45 AM, Damon Wang <damon.devops at gmail.com> wrote:
> Hi all,
>
> @Dustin has raised a problem about data-ordering problem:
>
>> "The issue is a race condition between message passing and database
>> replication. Imagine you have a large Buildbot installation with several
>> replicated MySQL servers and a redundant RabbitMQ cluster. One buildbot
>> master writes changes to a build to the database (an UPDATE operation), then
>> sends a message describing the change. On another master, some service gets
>> the message and queries a different MySQL server to see the build's new
>> status. If the message arrives before the database replication occurs, then
>> this master will see stale data. That will lead to a lot of subtle, rare
>> bugs. "
>
>
> The problem in this scene seems a consistency problem in mysql cluster? If
> mysql database on every node is strong
> consistency, this problem wont appear, right?
>
> But this is more involved with mysql cluster, does anybody know aboout this?
> Any helpful materials is welcomed.
>
> I will try to solve it through mq, if you have any idea, please leave a
> commit, thanks!
>
> Damon
>
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