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From Patrick Hunt <ph...@apache.org>
Subject Re: Zookeeper multiserver setup?
Date Wed, 09 May 2012 22:21:54 GMT
On Tue, May 8, 2012 at 3:46 PM, Something Something
<mailinglists19@gmail.com> wrote:
> Thanks.  Took your advice & cut down the number to 5 instances.  Confirmed
> that one of them is a leader & the rest are followers.  Now on to
> installing HBase.  Thanks again.

FWIW I typically recommend 3 or 5. 3 is fine, but 5 allows you to do
maintenance (take a server out of production) and still be able to
handle an unexpected failure w/o the service going down.

Patrick

> On Tue, May 8, 2012 at 3:19 PM, Jordan Zimmerman <jzimmerman@netflix.com>wrote:
>
>> For most uses, 3 instances is enough. For heavy usage, 5 instances can be
>> used. ZooKeeper write performance degrades with the number of instances
>> added. There's a lot of doc on the net about this.
>>
>> A ZNode is a data entry in the ZooKeeper database. An instance is a server
>> running the ZooKeeper software.
>>
>> -JZ
>>
>> On 5/8/12 3:13 PM, "Something Something" <mailinglists19@gmail.com> wrote:
>>
>> >We have a cluster of 17 machines.  Somewhere in the HBase documentation I
>> >read - usually we should divide by 2 & use an odd number.  May be I
>> >mis-read.  That's why I started Zookeeper on 9 machines.  I guess, I don't
>> >understand the difference between Nodes & Instance.  I expected ZKNodes
to
>> >be 9.  Please explain.  Thanks a lot for your help.
>> >
>> >On Tue, May 8, 2012 at 3:05 PM, Jordan Zimmerman
>> ><jzimmerman@netflix.com>wrote:
>> >
>> >> You have 9 instances? That's a lot. Why so many?
>> >>
>> >> I believe the "Node" field in the stat is the number of ZKNodes, not
>> >> instances in the ensemble. That stat looks good. It means that that
>> >> instance is serving requests as a "follower" instance (one of the
>> >> instances will be the leader).
>> >>
>> >> -JZ
>> >>
>> >> On 5/8/12 2:54 PM, "Something Something" <mailinglists19@gmail.com>
>> >>wrote:
>> >>
>> >> >Hmm...
>> >> >
>> >> >
>> >> >Trying 127.0.0.1...
>> >> >Connected to localhost.
>> >> >Escape character is '^]'.
>> >> >stat
>> >> >Zookeeper version: 3.3.4-cdh3u3--1, built on 01/26/2012 20:09 GMT
>> >> >Clients:
>> >> > /127.0.0.1:42510[0](queued=0,recved=1,sent=0)
>> >> >
>> >> >Latency min/avg/max: 0/0/0
>> >> >Received: 4
>> >> >Sent: 3
>> >> >Outstanding: 0
>> >> >Zxid: 0x100000000
>> >> >Mode: follower
>> >> >Node count: 11
>> >> >Connection closed by foreign host.
>> >> >
>> >> >
>> >> >Not sure I understand this output.  I have 9 nodes in the ensemble.
>> >> >
>> >> >On Tue, May 8, 2012 at 2:45 PM, Jordan Zimmerman
>> >> ><jzimmerman@netflix.com>wrote:
>> >> >
>> >> >> Yes - they should. Keep in mind that the zoo.cfg, and the ID file
>> >>must
>> >> >>be
>> >> >> correct and in agreement on each instance. You can do a stat on
each
>> >> >> instance to see what state it's in:
>> >> >>
>> >> >>    >telnet localhost 2181
>> >> >>     stat
>> >> >>
>> >> >> -JZ
>> >> >>
>> >> >> On 5/8/12 2:43 PM, "Something Something" <mailinglists19@gmail.com>
>> >> >>wrote:
>> >> >>
>> >> >> >Thanks Jordan.  Will definitely look at the cluster management
tool.
>> >> >>In
>> >> >> >the mean time, am I correct with my assumption in #4?  Once
all of
>> >>them
>> >> >> >are
>> >> >> >started they would automagically start talking to each other,
right?
>> >> >> >
>> >> >> >
>> >> >> >On Tue, May 8, 2012 at 2:36 PM, Jordan Zimmerman
>> >> >> ><jzimmerman@netflix.com>wrote:
>> >> >> >
>> >> >> >> Yes, you must start them all individually. ZooKeeper does
not
>> >> >>currently
>> >> >> >> have any cluster-wide management tools built in.
>> >> >> >>
>> >> >> >> FYI - we've open sourced a cluster management tool for
ZooKeeper.
>> >> >>Please
>> >> >> >> have a look:
>> >> >> >>
>> >> >> >>        https://github.com/Netflix/exhibitor
>> >> >> >>
>> >> >> >> On 5/8/12 2:31 PM, "Something Something"
>> >><mailinglists19@gmail.com>
>> >> >> >>wrote:
>> >> >> >>
>> >> >> >> >Hello,
>> >> >> >> >
>> >> >> >> >Trying to follow directions from here:
>> >> >> >> >
>> >> >> >>
>> >> >> >>
>> >> >>
>> >> >>
>> >>
>> >>
>> http://zookeeper.apache.org/doc/trunk/zookeeperAdmin.html#sc_zkMulitServe
>> >> >> >>r
>> >> >> >> >Setup
>> >> >> >> >
>> >> >> >> >to setup a cluster of zookeepers.
>> >> >> >> >
>> >> >> >> >Questions:
>> >> >> >> >
>> >> >> >> >1)  If everything is setup correctly, do I have to
go to each
>> >> >>machine
>> >> >> >>and
>> >> >> >> >start Zookeeper server in each of them individually?
>> >> >> >> >2)  I was thinking if I start it on one master machine
(well
>> >> >>there's no
>> >> >> >> >real master) then all zookeepers in the quorum would
be started,
>> >>but
>> >> >> >>this
>> >> >> >> >is not how it works correct?
>> >> >> >> >3)  If I start individually, then I get messages
saying the other
>> >> >> >> >zookeepers haven't started.  Is that just a warning?
>> >> >> >> >4)  When all of them are started, would they all
be able to talk
>> >>to
>> >> >> >>each
>> >> >> >> >other?
>> >> >> >> >
>> >> >> >> >Sorry for the dumb questions and thanks for the help.
>> >> >> >>
>> >> >> >>
>> >> >>
>> >> >>
>> >>
>> >>
>>
>>

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