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Zookeeper >> mail # dev >> Impacts of increasing ZooKeeper ticktime


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RE: Impacts of increasing ZooKeeper ticktime
Pat & Camille, Thanks for your response.

> I don't think you need to touch the tickTime here. See "maxSessionTimeout"
> here:
> http://zookeeper.apache.org/doc/r3.3.3/zookeeperAdmin.html#sc_advancedConf
> iguration
> (hbase has a similar issue, that's why we added this feature initially).

I've tried this maxSessionTimeout. This satisfies my customer's requirement.
I also agree that, we still need to fix the GC issue. This has been
discussed with our customer and "maxSessionTimeout" is provided to unblock
them temporarily.

>It does mean that if you
> have clients writing directly to the ZK client (instead of through a
> wrapper you provide), you need to encourage people not to use MAX_INT in
> their default client setup unless they need the long timeout.

This is clear and in fact we are using the session timeout value of 30
seconds only for many use cases like Namenode HA.

Thanks again for your quick response.

> -----Original Message-----
> From: Fournier, Camille F. [mailto:[EMAIL PROTECTED]]
> Sent: Wednesday, September 14, 2011 11:48 PM
> To: '[EMAIL PROTECTED]'; '[EMAIL PROTECTED]'
> Subject: RE: Impacts of increasing ZooKeeper ticktime
>
> Session timeout is negotiated though eh? So if only the clients that need
> the long GC session expiration time set their client session timeout to
> MAX_INT, other clients can keep it at a lower number and not have a
> problem. That's how we have resolved the issue. It does mean that if you
> have clients writing directly to the ZK client (instead of through a
> wrapper you provide), you need to encourage people not to use MAX_INT in
> their default client setup unless they need the long timeout.
>
> C
>
> -----Original Message-----
> From: Patrick Hunt [mailto:[EMAIL PROTECTED]]
> Sent: Wednesday, September 14, 2011 1:44 PM
> To: [EMAIL PROTECTED]; [EMAIL PROTECTED]
> Subject: Re: Impacts of increasing ZooKeeper ticktime
>
> On Wed, Sep 14, 2011 at 3:23 AM, Laxman <[EMAIL PROTECTED]> wrote:
> > Our customers are recently complaining about zookeeper client session
> > timeouts.
> >
> > When analyzed its found that timeouts are due to heavy GC activity on
> > Clients.
> >
> > So, they wanted to increase the session timeouts to 3 minutes which
> requires
> > the ticktime to be increased to atleast 9 seconds.
> >
>
> I assume you've talked to them about fixing their gc issue at some
> point? Rather than band-aiding it? :-)
>
> I don't think you need to touch the tickTime here. See "maxSessionTimeout"
> here:
> http://zookeeper.apache.org/doc/r3.3.3/zookeeperAdmin.html#sc_advancedConf
> iguration
> (hbase has a similar issue, that's why we added this feature initially).
>
> Really though they should fix the gc issue - setting the session
> timeout higher means that their sessions will be expiring only after a
> much longer time. Any reliance on this - such as for leader election
> fail-over, will now take much more time. In your example it would take
> 3 minutes for the other clients to notice when a client with the
> particular session has become unavailable. Perhaps it doesn't matter
> in your use case, but you are now likely to get complains about ZK not
> being responsive. ;-)
>
> Regards,
>
> Patrick