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From "Pablo Medina (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-9087) Handlers being blocked during reads
Date Wed, 31 Jul 2013 16:45:50 GMT

    [ https://issues.apache.org/jira/browse/HBASE-9087?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13725406#comment-13725406
] 

Pablo Medina commented on HBASE-9087:
-------------------------------------

Elliot, did you run that benchmark ? did it improve the performance under concurrency?
                
> Handlers being blocked during reads
> -----------------------------------
>
>                 Key: HBASE-9087
>                 URL: https://issues.apache.org/jira/browse/HBASE-9087
>             Project: HBase
>          Issue Type: Bug
>          Components: Performance
>    Affects Versions: 0.94.7, 0.95.1
>            Reporter: Pablo Medina
>            Assignee: Elliott Clark
>            Priority: Critical
>             Fix For: 0.98.0, 0.95.2, 0.94.11
>
>         Attachments: HBASE-9087-0.patch, HBASE-9087-1.patch
>
>
> I'm having a lot of handlers (90 - 300 aprox) being blocked when reading rows. They are
blocked during changedReaderObserver registration.
> Lars Hofhansl suggests to change the implementation of changedReaderObserver from CopyOnWriteList
to ConcurrentHashMap.
> Here is a stack trace: 
> "IPC Server handler 99 on 60020" daemon prio=10 tid=0x0000000041c84000 nid=0x2244 waiting
on condition [0x00007ff51fefd000]
>    java.lang.Thread.State: WAITING (parking)
>         at sun.misc.Unsafe.park(Native Method)
>         - parking to wait for  <0x00000000c5c13ae8> (a java.util.concurrent.locks.ReentrantLock$NonfairSync)
>         at java.util.concurrent.locks.LockSupport.park(LockSupport.java:156)
>         at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:811)
>         at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:842)
>         at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1178)
>         at java.util.concurrent.locks.ReentrantLock$NonfairSync.lock(ReentrantLock.java:186)
>         at java.util.concurrent.locks.ReentrantLock.lock(ReentrantLock.java:262)
>         at java.util.concurrent.CopyOnWriteArrayList.addIfAbsent(CopyOnWriteArrayList.java:553)
>         at java.util.concurrent.CopyOnWriteArraySet.add(CopyOnWriteArraySet.java:221)
>         at org.apache.hadoop.hbase.regionserver.Store.addChangedReaderObserver(Store.java:1085)
>         at org.apache.hadoop.hbase.regionserver.StoreScanner.<init>(StoreScanner.java:138)
>         at org.apache.hadoop.hbase.regionserver.Store.getScanner(Store.java:2077)
>         at org.apache.hadoop.hbase.regionserver.HRegion$RegionScannerImpl.<init>(HRegion.java:3755)
>         at org.apache.hadoop.hbase.regionserver.HRegion.instantiateRegionScanner(HRegion.java:1804)
>         at org.apache.hadoop.hbase.regionserver.HRegion.getScanner(HRegion.java:1796)
>         at org.apache.hadoop.hbase.regionserver.HRegion.getScanner(HRegion.java:1771)
>         at org.apache.hadoop.hbase.regionserver.HRegion.get(HRegion.java:4776)
>         at org.apache.hadoop.hbase.regionserver.HRegion.get(HRegion.java:4750)
>         at org.apache.hadoop.hbase.regionserver.HRegionServer.get(HRegionServer.java:2152)
>         at org.apache.hadoop.hbase.regionserver.HRegionServer.multi(HRegionServer.java:3700)
>         at sun.reflect.GeneratedMethodAccessor26.invoke(Unknown Source)
>         at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
>         at java.lang.reflect.Method.invoke(Method.java:597)
>         at org.apache.hadoop.hbase.ipc.WritableRpcEngine$Server.call(WritableRpcEngine.java:320)
>         at org.apache.hadoop.hbase.ipc.HBaseServer$Handler.run(HBaseServer.java:1426)
>       

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