Zookeeper to MongoDB transition

[Kapil Thangavelu]

On Tue, Jun 12, 2012 at 9:21 PM, Gustavo Niemeyer <
gustavo.niemeyer at canonical.com> wrote:

> On Tue, Jun 12, 2012 at 8:15 PM, Clint Byrum <clint at ubuntu.com> wrote:
> > Was there any public discussion about the reasons to get rid of
> Zookeeper,
> > and/or the reasons to choose MongoDB?
>
> Yes, there were public conversations about that on #juju-dev and in
> the public room where we were meeting at UDS. We hadn't started
> anything because we didn't have the man power, but Aram joined us a
> couple of weeks ago and is researching to see how the scenario looks
> like. This message is part of the outcome of that incipient initial
> research, so there's no reason to panic really.
>
>
I'm curious what this means for juju wrt to being an observation based
system. Its currently a little light on details, and i look forward to
seeing some of the model schemas. But wrt to juju's usage currently we use
zk as our observable hierarchical filesystem. With mongodb, we can get some
observation capabilities with tailable cursors on capped collections,
however that effectively entails either a timing gap from insertion into
the secondary capped collection (ie non atomic changes to two collections),
a change to a poll/query model, or using capped collections as a primary
data store afaics. Could someone elaborate on the observation and
reliability semantics expected with a change to mongodb?


cheers,

Kapil
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