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Date: Fri, 18 May 2012 13:55:16 -0700
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Subject: Re: cluster member was switched to standalone, detectable?
From: Adam Rosien <adam@rosien.net>
To: user@zookeeper.apache.org
Cc: "zookeeper-user@hadoop.apache.org" <zookeeper-user@hadoop.apache.org>
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Do the four-letter words tell me if a service joined the quorum correctly?
What commands and responses will tell me?

How do I know what cluster it joined? What if nodes X & Y are in cluster A
but Z is in cluster B, should there be a cluster identifier to distinguish
membership?

On Fri, May 18, 2012 at 12:05 PM, Patrick Hunt <phunt@apache.org> wrote:

> That would detect it, I don't think it's avoidable in the sense that
> we can't detect that type of mis-configuration and somehow handle it
> (ie stop). Your best bet would be to automate the process (and test
> that ahead of time), or bring up the new server with the client port
> set to something previously unused, then verify, then restart it with
> the client port set as it was originally. I often do this when
> debugging issues. (but that itself might cause problems wrt config
> typos). Another option is to use iptables (etc...) to turn off access
> to clients until you've verified the server joined the quorum
> correctly, then turn off the filter.
>
> Patrick
>
> On Fri, May 18, 2012 at 11:51 AM, Jordan Zimmerman
> <jzimmerman@netflix.com> wrote:
> > ZooKeeper has a telnet style interface for periodic querying.
> >
> > You could also use Exhibitor and query it's REST API periodically. I
> > should probably add alerting to Exhibitor for this kind of thing.
> >
> > -JZ
> >
> > On 5/18/12 10:34 AM, "Adam Rosien" <adam@rosien.net> wrote:
> >
> >>We have a 5-member 3.3.3 cluster. One of the node's configurations was
> >>accidentally changed, and that node went into "standalone" mode, thinking
> >>it was a single-node cluster. However, all our zk clients still had the
> >>address of this server, and when connected obviously got missing or wrong
> >>data.
> >>
> >>Is this situation avoidable somehow?
> >>
> >>.. Adam
> >
>

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