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From Mahadev Konar <maha...@yahoo-inc.com>
Subject Re: Zookeeper EventThread and SendThread
Date Thu, 20 May 2010 19:11:46 GMT

Hi Nick,
 These threads are spawned with each zookeeper client handle. As soon as you
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,
> 
> Question regarding zookeeper's EventThread and SendThread. I'm not quite sure
> what these are used for but a stacktrace of our client application contains
> lines similar to
> 
> "pool-2-thread-20-EventThread" daemon prio=10 tid=0x00002aac3cb29c00 nid=0x75d
> waiting on condition [0x000000006b080000..0x000000006b080b10]
>    java.lang.Thread.State: WAITING (parking)
>         at sun.misc.Unsafe.park(Native Method)
>         - parking to wait for  <0x00002aab1f577250> (a
> java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
>         at java.util.concurrent.locks.LockSupport.park(LockSupport.java:158)
>         at 
> java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(Ab
> stractQueuedSynchronizer.java:1925)
>         at 
> java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:358)
>         at 
> org.apache.zookeeper.ClientCnxn$EventThread.run(ClientCnxn.java:414)
> 
> "pool-2-thread-20-SendThread" daemon prio=10 tid=0x00002aac3c35d400 nid=0x75c
> runnable [0x0000000070ede000..0x0000000070edeb90]
>    java.lang.Thread.State: RUNNABLE
>         at sun.nio.ch.EPollArrayWrapper.epollWait(Native Method)
>         at sun.nio.ch.EPollArrayWrapper.poll(EPollArrayWrapper.java:215)
>         at sun.nio.ch.EPollSelectorImpl.doSelect(EPollSelectorImpl.java:65)
>         at sun.nio.ch.SelectorImpl.lockAndDoSelect(SelectorImpl.java:69)
>         - locked <0x00002aab1f571d08> (a sun.nio.ch.Util$1)
>         - locked <0x00002aab1f571cf0> (a
> java.util.Collections$UnmodifiableSet)
>         - locked <0x00002aab1f5715b8> (a sun.nio.ch.EPollSelectorImpl)
>         at sun.nio.ch.SelectorImpl.select(SelectorImpl.java:80)
>         at org.apache.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:921)
> 
> There are pairs of threads ranging from thread-1 to thread-50 and also
> multiple pairs of these threads.  As in pool-2-thread-20-SendThread is the
> name of multiple threads in the trace.  I'm debugging some load issues with
> our system and am suspicious that the large amount of zookeeper threads is
> contributing. Would anyone be able to elaborate on the purpose of these
> threads and how they are spawned?
> 
> Thanks,
> 
> Nick Bailey
> Rackspace Hosting
> Software Developer, Email & Apps
> nicholas.bailey@rackspace.com
> 


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