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From Jordan Zimmerman <jzimmer...@netflix.com>
Subject Re: cluster member was switched to standalone, detectable?
Date Fri, 18 May 2012 20:58:45 GMT
FYI - for an example you can look at the Exhibitor source.


It issues an 'ruok' and then a 'srvr'.


On 5/18/12 1:57 PM, "Jordan Zimmerman" <jzimmerman@netflix.com> wrote:

>The 'srvr' command lists what mode the instance thinks it's in.
>Unfortunately, you have to manually parse it. If there's a quorum issue it
>outputs something like "This ZooKeeper is not serving requests".
>On 5/18/12 1:55 PM, "Adam Rosien" <adam@rosien.net> wrote:
>>Do the four-letter words tell me if a service joined the quorum
>>What commands and responses will tell me?
>>How do I know what cluster it joined? What if nodes X & Y are in cluster
>>but Z is in cluster B, should there be a cluster identifier to
>>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
>>> >>accidentally changed, and that node went into "standalone" mode,
>>> >>it was a single-node cluster. However, all our zk clients still had
>>> >>address of this server, and when connected obviously got missing or
>>> >>data.
>>> >>
>>> >>Is this situation avoidable somehow?
>>> >>
>>> >>.. Adam
>>> >

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