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Date: Thu, 20 May 2010 12:11:46 -0700
Subject: Re: Zookeeper EventThread and SendThread
From: Mahadev Konar <mahadev@yahoo-inc.com>
To: <zookeeper-user@hadoop.apache.org>
Message-ID: <C81AD782.366CC%mahadev@yahoo-inc.com>
Thread-Topic: Zookeeper EventThread and SendThread
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Hi Nick,
 These threads are spawned with each zookeeper client handle. As soon as yo=
u
create a zookeeper client object these threads are spawned.

Are yu creating too many zookeeper client objects in your application?

Htanks
mahadev

On 5/20/10 11:30 AM, "Nick Bailey" <nicholas.bailey@rackspace.com> wrote:

> Hey guys,
>=20
> Question regarding zookeeper's EventThread and SendThread. I'm not quite =
sure
> what these are used for but a stacktrace of our client application contai=
ns
> lines similar to
>=20
> "pool-2-thread-20-EventThread" daemon prio=3D10 tid=3D0x00002aac3cb29c00 nid=3D=
0x75d
> waiting on condition [0x000000006b080000..0x000000006b080b10]
>  =A0 java.lang.Thread.State: WAITING (parking)
>  =A0 =A0 =A0 =A0at sun.misc.Unsafe.park(Native Method)
>  =A0 =A0 =A0 =A0- parking to wait for =A0<0x00002aab1f577250> (a
> java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
>  =A0 =A0 =A0 =A0at java.util.concurrent.locks.LockSupport.park(LockSupport.java:1=
58)
>  =A0 =A0 =A0 =A0at=20
> java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.awa=
it(Ab
> stractQueuedSynchronizer.java:1925)
>  =A0 =A0 =A0 =A0at=20
> java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:35=
8)
>  =A0 =A0 =A0 =A0at=20
> org.apache.zookeeper.ClientCnxn$EventThread.run(ClientCnxn.java:414)
>=20
> "pool-2-thread-20-SendThread" daemon prio=3D10 tid=3D0x00002aac3c35d400 nid=3D0=
x75c
> runnable [0x0000000070ede000..0x0000000070edeb90]
>  =A0 java.lang.Thread.State: RUNNABLE
>  =A0 =A0 =A0 =A0at sun.nio.ch.EPollArrayWrapper.epollWait(Native Method)
>  =A0 =A0 =A0 =A0at sun.nio.ch.EPollArrayWrapper.poll(EPollArrayWrapper.java:215)
>  =A0 =A0 =A0 =A0at sun.nio.ch.EPollSelectorImpl.doSelect(EPollSelectorImpl.java:6=
5)
>  =A0 =A0 =A0 =A0at sun.nio.ch.SelectorImpl.lockAndDoSelect(SelectorImpl.java:69)
>  =A0 =A0 =A0 =A0- locked <0x00002aab1f571d08> (a sun.nio.ch.Util$1)
>  =A0 =A0 =A0 =A0- locked <0x00002aab1f571cf0> (a
> java.util.Collections$UnmodifiableSet)
>  =A0 =A0 =A0 =A0- locked <0x00002aab1f5715b8> (a sun.nio.ch.EPollSelectorImpl)
>  =A0 =A0 =A0 =A0at sun.nio.ch.SelectorImpl.select(SelectorImpl.java:80)
>  =A0 =A0 =A0 =A0at org.apache.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java=
:921)
>=20
> There are pairs of threads ranging from thread-1 to thread-50 and also
> multiple pairs of these threads. =A0As in pool-2-thread-20-SendThread is th=
e
> name of multiple threads in the trace. =A0I'm debugging some load issues wi=
th
> our system and am suspicious that the large amount of zookeeper threads i=
s
> contributing. Would anyone be able to elaborate on the purpose of these
> threads and how they are spawned?
>=20
> Thanks,
>=20
> Nick Bailey
> Rackspace Hosting
> Software Developer, Email & Apps
> nicholas.bailey@rackspace.com
>=20