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From: Jordan Zimmerman <jzimmerman@netflix.com>
To: "user@zookeeper.apache.org" <user@zookeeper.apache.org>
CC: "zookeeper-user@hadoop.apache.org" <zookeeper-user@hadoop.apache.org>
Subject: Re: cluster member was switched to standalone, detectable?
Thread-Topic: cluster member was switched to standalone, detectable?
Thread-Index: AQHNNRyYiNrJaMyFuU+WyU2j6bXbKJbP5BkAgAB5i4CAAB6JAP//izeA
Date: Fri, 18 May 2012 20:57:17 +0000
Message-ID: <CBDC057B.1CC62%jzimmerman@netflix.com>
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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".

-JZ

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 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
>> >
>>