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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-3654) Weird blocking between getOnlineRegion and createRegionLoad
Date Thu, 24 Mar 2011 06:22:05 GMT

    [ https://issues.apache.org/jira/browse/HBASE-3654?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13010572#comment-13010572
] 

stack commented on HBASE-3654:
------------------------------

I see. You can't use CopyOnWriteArrayList/Set because online regions is a Map.  I also see
that we are hitting the Arrays.copyOf because we are not presizing the ArrayList.  Duh.  CSKLM
has this to say about getting its size though:

"Beware that, unlike in most collections, the size method is not a constant-time operation.
Because of the asynchronous nature of these maps, determining the current number of elements
requires a traversal of the elements. Additionally, the bulk operations putAll, equals, and
clear are not guaranteed to be performed atomically. For example, an iterator operating concurrently
with a putAll operation might view only some of the added elements."

So getting size might be a little expensive, but probably way cheaper than resizing and array
multiple times.

We don't need a sorted list so CHM would look like the better way to go?

Thanks for working on this Subbu.



> Weird blocking between getOnlineRegion and createRegionLoad
> -----------------------------------------------------------
>
>                 Key: HBASE-3654
>                 URL: https://issues.apache.org/jira/browse/HBASE-3654
>             Project: HBase
>          Issue Type: Bug
>    Affects Versions: 0.90.1
>            Reporter: Jean-Daniel Cryans
>            Priority: Blocker
>             Fix For: 0.90.2
>
>         Attachments: ConcurrentHM, ConcurrentSKLM, CopyOnWrite, TestOnlineRegions.java,
hashmap
>
>
> Saw this when debugging something else:
> {code}
> "regionserver60020" prio=10 tid=0x00007f538c1c0000 nid=0x4c7 runnable [0x00007f53931da000]
>    java.lang.Thread.State: RUNNABLE
> 	at org.apache.hadoop.hbase.regionserver.Store.getStorefilesIndexSize(Store.java:1380)
> 	at org.apache.hadoop.hbase.regionserver.HRegionServer.createRegionLoad(HRegionServer.java:916)
> 	- locked <0x0000000672aa0a00> (a java.util.concurrent.ConcurrentSkipListMap)
> 	at org.apache.hadoop.hbase.regionserver.HRegionServer.buildServerLoad(HRegionServer.java:767)
> 	- locked <0x0000000656f62710> (a java.util.HashMap)
> 	at org.apache.hadoop.hbase.regionserver.HRegionServer.tryRegionServerReport(HRegionServer.java:722)
> 	at org.apache.hadoop.hbase.regionserver.HRegionServer.run(HRegionServer.java:591)
> 	at java.lang.Thread.run(Thread.java:662)
> "IPC Reader 9 on port 60020" prio=10 tid=0x00007f538c1be000 nid=0x4c6 waiting for monitor
entry [0x00007f53932db000]
>    java.lang.Thread.State: BLOCKED (on object monitor)
> 	at org.apache.hadoop.hbase.regionserver.HRegionServer.getFromOnlineRegions(HRegionServer.java:2295)
> 	- waiting to lock <0x0000000656f62710> (a java.util.HashMap)
> 	at org.apache.hadoop.hbase.regionserver.HRegionServer.getOnlineRegion(HRegionServer.java:2307)
> 	at org.apache.hadoop.hbase.regionserver.HRegionServer.getRegion(HRegionServer.java:2333)
> 	at org.apache.hadoop.hbase.regionserver.HRegionServer$QosFunction.isMetaRegion(HRegionServer.java:379)
> 	at org.apache.hadoop.hbase.regionserver.HRegionServer$QosFunction.apply(HRegionServer.java:422)
> 	at org.apache.hadoop.hbase.regionserver.HRegionServer$QosFunction.apply(HRegionServer.java:361)
> 	at org.apache.hadoop.hbase.ipc.HBaseServer.getQosLevel(HBaseServer.java:1126)
> 	at org.apache.hadoop.hbase.ipc.HBaseServer$Connection.processData(HBaseServer.java:982)
> 	at org.apache.hadoop.hbase.ipc.HBaseServer$Connection.readAndProcess(HBaseServer.java:946)
> 	at org.apache.hadoop.hbase.ipc.HBaseServer$Listener.doRead(HBaseServer.java:522)
> 	at org.apache.hadoop.hbase.ipc.HBaseServer$Listener$Reader.run(HBaseServer.java:316)
> 	- locked <0x0000000656e60068> (a org.apache.hadoop.hbase.ipc.HBaseServer$Listener$Reader)
> 	at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
> 	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
> 	at java.lang.Thread.run(Thread.java:662)
> ...
> "IPC Reader 0 on port 60020" prio=10 tid=0x00007f538c08b000 nid=0x4bd waiting for monitor
entry [0x00007f5393be4000]
>    java.lang.Thread.State: BLOCKED (on object monitor)
> 	at org.apache.hadoop.hbase.regionserver.HRegionServer.getFromOnlineRegions(HRegionServer.java:2295)
> 	- waiting to lock <0x0000000656f62710> (a java.util.HashMap)
> 	at org.apache.hadoop.hbase.regionserver.HRegionServer.getOnlineRegion(HRegionServer.java:2307)
> 	at org.apache.hadoop.hbase.regionserver.HRegionServer.getRegion(HRegionServer.java:2333)
> 	at org.apache.hadoop.hbase.regionserver.HRegionServer$QosFunction.isMetaRegion(HRegionServer.java:379)
> 	at org.apache.hadoop.hbase.regionserver.HRegionServer$QosFunction.apply(HRegionServer.java:422)
> 	at org.apache.hadoop.hbase.regionserver.HRegionServer$QosFunction.apply(HRegionServer.java:361)
> 	at org.apache.hadoop.hbase.ipc.HBaseServer.getQosLevel(HBaseServer.java:1126)
> 	at org.apache.hadoop.hbase.ipc.HBaseServer$Connection.processData(HBaseServer.java:982)
> 	at org.apache.hadoop.hbase.ipc.HBaseServer$Connection.readAndProcess(HBaseServer.java:946)
> 	at org.apache.hadoop.hbase.ipc.HBaseServer$Listener.doRead(HBaseServer.java:522)
> 	at org.apache.hadoop.hbase.ipc.HBaseServer$Listener$Reader.run(HBaseServer.java:316)
> 	- locked <0x0000000656e635c8> (a org.apache.hadoop.hbase.ipc.HBaseServer$Listener$Reader)
> 	at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
> 	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
> 	at java.lang.Thread.run(Thread.java:662)
> {code}
> All the readers are blocked! I have the feeling something much better could be done.

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