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https://issues.apache.org/jira/browse/PHOENIX-3111?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15398124#comment-15398124
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Sergey Soldatov commented on PHOENIX-3111:
------------------------------------------
[~lhofhansl] That's exactly I'm trying to say. The workflow is following:
1. We get read lock when we start writing local indexes
2. when memstore reach threshold, flushes happen. Since they use read (shared)
lock they happen without any problem until someone tries to obtain write lock.
3. at one moment we decide to split and try to acquire write lock.
4. Since that moment all attempts to get read lock will be blocked. I.e. no
more flushes will happen. But we continue to fill memstore with local index
batches and finally we get RTBE.
The dump from the description demonstrates exactly the moment when split is
waiting for our scan and flush is blocked by split.
> Possible Deadlock/delay while building index, upsert select, delete rows at
> server
> ----------------------------------------------------------------------------------
>
> Key: PHOENIX-3111
> URL: https://issues.apache.org/jira/browse/PHOENIX-3111
> Project: Phoenix
> Issue Type: Bug
> Reporter: Sergio Peleato
> Assignee: Rajeshbabu Chintaguntla
> Priority: Critical
> Fix For: 4.8.1
>
> Attachments: PHOENIX-3111.patch
>
>
> There is a possible deadlock while building local index or running upsert
> select, delete at server. The situation might happen in this case.
> In the above queries we scan mutations from table and write back to same
> table in that case there is a chance of memstore might reach the threshold of
> blocking memstore size then RegionTooBusyException might be thrown back to
> client and queries might retry scanning.
> Let's suppose if we take a local index build index case we first scan from
> the data table and prepare index mutations and write back to same table.
> So there is chance of memstore full as well in that case we try to flush the
> region. But if the split happen in between then split might be waiting for
> write lock on the region to close and flush wait for readlock because the
> write lock in the queue until the local index build completed. Local index
> build won't complete because we are not allowed to write until there is
> flush. This might not be complete deadlock situation but the queries might
> take lot of time to complete in this cases.
> {noformat}
> "regionserver//192.168.0.53:16201-splits-1469165876186" #269 prio=5
> os_prio=31 tid=0x00007f7fb2050800 nid=0x1c033 waiting on condition
> [0x0000000139b68000]
> java.lang.Thread.State: WAITING (parking)
> at sun.misc.Unsafe.park(Native Method)
> - parking to wait for <0x00000006ede72550> (a
> java.util.concurrent.locks.ReentrantReadWriteLock$NonfairSync)
> at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
> at
> java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:836)
> at
> java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:870)
> at
> java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1199)
> at
> java.util.concurrent.locks.ReentrantReadWriteLock$WriteLock.lock(ReentrantReadWriteLock.java:943)
> at
> org.apache.hadoop.hbase.regionserver.HRegion.doClose(HRegion.java:1422)
> at
> org.apache.hadoop.hbase.regionserver.HRegion.close(HRegion.java:1370)
> - locked <0x00000006ede69d00> (a java.lang.Object)
> at
> org.apache.hadoop.hbase.regionserver.SplitTransactionImpl.stepsBeforePONR(SplitTransactionImpl.java:394)
> at
> org.apache.hadoop.hbase.regionserver.SplitTransactionImpl.createDaughters(SplitTransactionImpl.java:278)
> at
> org.apache.hadoop.hbase.regionserver.SplitTransactionImpl.execute(SplitTransactionImpl.java:561)
> at
> org.apache.hadoop.hbase.regionserver.SplitRequest.doSplitting(SplitRequest.java:82)
> at
> org.apache.hadoop.hbase.regionserver.SplitRequest.run(SplitRequest.java:154)
> at
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
> at java.lang.Thread.run(Thread.java:745)
> Locked ownable synchronizers:
> - <0x00000006ee132098> (a
> java.util.concurrent.ThreadPoolExecutor$Worker)
> {noformat}
> {noformat}
> "MemStoreFlusher.0" #170 prio=5 os_prio=31 tid=0x00007f7fb6842000 nid=0x19303
> waiting on condition [0x00000001388e9000]
> java.lang.Thread.State: WAITING (parking)
> at sun.misc.Unsafe.park(Native Method)
> - parking to wait for <0x00000006ede72550> (a
> java.util.concurrent.locks.ReentrantReadWriteLock$NonfairSync)
> at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
> at
> java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:836)
> at
> java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireShared(AbstractQueuedSynchronizer.java:967)
> at
> java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireShared(AbstractQueuedSynchronizer.java:1283)
> at
> java.util.concurrent.locks.ReentrantReadWriteLock$ReadLock.lock(ReentrantReadWriteLock.java:727)
> at
> org.apache.hadoop.hbase.regionserver.HRegion.flushcache(HRegion.java:1986)
> at
> org.apache.hadoop.hbase.regionserver.HRegion.flush(HRegion.java:1950)
> at
> org.apache.hadoop.hbase.regionserver.MemStoreFlusher.flushRegion(MemStoreFlusher.java:501)
> at
> org.apache.hadoop.hbase.regionserver.MemStoreFlusher.flushRegion(MemStoreFlusher.java:471)
> at
> org.apache.hadoop.hbase.regionserver.MemStoreFlusher.access$800(MemStoreFlusher.java:75)
> at
> org.apache.hadoop.hbase.regionserver.MemStoreFlusher$FlushHandler.run(MemStoreFlusher.java:259)
> at java.lang.Thread.run(Thread.java:745)
> {noformat}
> As a fix we need to block region splits if building index, upsert select,
> delete rows running at server.
> Thanks [~sergey.soldatov] for the help in understanding the bug and analyzing
> it. [~speleato] for finding it.
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