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From Vishal Kher <vishalm...@gmail.com>
Subject Re: ZOOKEEPER-107 - Allow dynamic changes to server cluster membership
Date Mon, 03 May 2010 17:26:58 GMT
Hi Henry,

Thanks for the info. I will spend some more time to understand the issues
before starting with the implementation. I will let you know if I have any
questions (which I am sure I will).

Just to clarify, "by solved issue" you mean from design perspective and not
from implementation right?
Regards,
-Vishal
On Mon, May 3, 2010 at 1:16 PM, Henry Robinson <henry@cloudera.com> wrote:

> Hi Vishal -
>
> Great that you're interested in contributing! This would be a really neat
> feature to get into ZK.
>
> The documentation that exists is essentially all on the JIRA. I had a patch
> that 'worked' but was nowhere near commit-ready. I'm trying to dig it up,
> but it appears it may have gone to the great bit-bucket in the sky. Trunk
> has moved sufficiently that a new patch would be required anyhow.
>
> There were two main difficulties with this issue. The first is changing the
> voting protocol to cope with changes in views. Since proposals are
> pipelined, the leader needs to keep track of what the view was that should
> vote for a proposal. IIRC, the other subtlety is making sure that when a
> view change is proposed, a quorum of votes is received from both the
> outgoing view and the incoming one. Otherwise it's possible to transition
> to
> a 'dead' view in which no progress can be made.
>
> The second is to figure out the metadata management - how do we 'find'
> ZooKeeper servers if the ensemble may have moved onto a completely separate
> set of machines? That is, if the original ensemble was on A, B, C and the
> current ensemble is D, E, F - where do we look to find where the ensemble
> is
> located?
>
> The first is a solved issue, the second is more a matter of taste than
> designing distributed protocols.
>
> Really happy to help with this issue - I'd love to see it get resurrected.
>
> cheers,
> Henry
>
> On 3 May 2010 07:25, Vishal K <vishalmlst@gmail.com> wrote:
>
> > Hi Henry,
> >
> > I just commented on the Jira. I would be happy to contribute.
> > Please advise on the current status and next steps. Thanks.
> >
> > Regards,
> > -Vishal
> >
>
>
>
> --
> Henry Robinson
> Software Engineer
> Cloudera
> 415-994-6679
>

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