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From Chris Nauroth <cnaur...@apache.org>
Subject Re: four letter commands not working as expected.
Date Wed, 04 Jan 2017 20:55:20 GMT
Yes, FWIW, I've generally had better success monitoring "stat", "srvr" or
"mntr".  Any of these can tell you the server's leader/follower state, and
the latter offers a rich set of usage metrics.  There are more details in
the documentation here:

https://zookeeper.apache.org/doc/r3.4.9/zookeeperAdmin.html#sc_zkCommands


Chris Nauroth

On Wed, Nov 30, 2016 at 10:52 AM, Michael Han <hanm@cloudera.com> wrote:

> 'ruok' is the very basic sanity check of the ZooKeeper server process - it
> will return ok as long as the server process is up and reachable through
> network (in fact, the server does not nothing but immediately return ok
> upon receives 'ruok' request).
> 'ruup' does seem a better naming semantically to me.
>
> On Tue, Nov 29, 2016 at 5:10 PM, Ben Sherman <bensherman@gmail.com> wrote:
>
> > I expect if none of the 4 letter commands except ruok give a response,
> then
> > the server is definitively not okay.  ruup vs ruok maybe? We see the
> server
> > popping into a looking state quite often, and it's the cause of 100% of
> our
> > outages involving zookeeper.  This isn't an initial state, it's down
> until
> > a restart.
> >
> > On Tue, Nov 29, 2016 at 3:08 PM, Flavio Junqueira <fpj@apache.org>
> wrote:
> >
> > > It looks like the server is in the LOOKING state, so it is not serving
> > > request but it is up. I'd say that ruok should return imok as long as
> the
> > > server is up, it's not necessarily a health check.  We could review the
> > > semantics of the commands if this behavior and others are confusing.
> > >
> > > -Flavio
> > >
> > >
> > > > On 29 Nov 2016, at 19:54, Ben Sherman <bensherman@gmail.com> wrote:
> > > >
> > > > Four letter word ruok is returning imok when the server is decidedly
> > not
> > > > okay - is this the expected behavior?
> > > >
> > > > bsherman@zk1:~$ nc localhost 2181 <<< mntr
> > > > This ZooKeeper instance is not currently serving requests
> > > > bsherman@zk1:~$ nc localhost 2181 <<< ruok
> > > > imok
> > > >
> > > > I'm running 3.4.9.
> > > >
> > > > --ben
> > >
> > >
> >
>
>
>
> --
> Cheers
> Michael.
>

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