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