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https://issues.apache.org/jira/browse/HBASE-21200?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16649819#comment-16649819
]
ramkrishna.s.vasudevan commented on HBASE-21200:
------------------------------------------------
I now get this patch better. So previously without your V2 patch - say we got
the rows with 199996 and 199995 . And after that the startKV would have been
set at 199995. Now from then on the previous rows 199994, 199993 etc. would be
compared with 199995 and every time it will be lower and this condition
{code}
if (stopSkippingKVsIfNextRow && // for backwardSeek() stay in the
startKV != null && // boundaries of a single row
segment.compareRows(next, startKV) > 0) {
current = null;
return;
}
{code}
Will always be false and hence making the entire while loop to go ahead till
you reach the 10000 row (as in this eg).
Now with this patch every time you compare 19994 with its first row key only.
So that while loop inside updateCurrent() is comes out faster. But the
seekToPrevoiusRow() will still keep going till the 10000 row correct? It is
that previously both seekToPreviousRow() and updateCurrent were doing n*n
totally ( n being the number of rows ) and now only the seekToPreviousRow()
will go through n rows. Am I getting this right?
> Memstore flush doesn't finish because of seekToPreviousRow() in memstore
> scanner.
> ---------------------------------------------------------------------------------
>
> Key: HBASE-21200
> URL: https://issues.apache.org/jira/browse/HBASE-21200
> Project: HBase
> Issue Type: Bug
> Components: Scanners
> Reporter: dongjin2193.jeon
> Assignee: Toshihiro Suzuki
> Priority: Major
> Attachments: HBASE-21200-UT.patch, HBASE-21200.master.001.patch,
> HBASE-21200.master.002.patch, RegionServerJstack.log
>
>
> The issue of delaying memstore flush still occurs after backport hbase-15871.
> Reverse scan takes a long time to seek previous row in the memstore full of
> deleted cells.
>
> jstack :
> "MemStoreFlusher.0" #114 prio=5 os_prio=0 tid=0x00007fa3d0729000 nid=0x486a
> waiting on condition [0x00007fa3b9b6b000]
> java.lang.Thread.State: WAITING (parking)
> at sun.misc.Unsafe.park(Native Method)
> - parking to wait for <0x00000000a465fe60> (a
> java.util.concurrent.locks.ReentrantLock$NonfairSync)
> at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175)
> at
> java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(AbstractQueuedSynchronizer.java:836)
> at
> java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(AbstractQueuedSynchronizer.java:870)
> at
> java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(AbstractQueuedSynchronizer.java:1199)
> at
> java.util.concurrent.locks.ReentrantLock$NonfairSync.lock(ReentrantLock.java:209)
> at
> java.util.concurrent.locks.ReentrantLock.lock(ReentrantLock.java:285)
> at
> org.apache.hadoop.hbase.regionserver.*StoreScanner.updateReaders(StoreScanner.java:695)*
> at
> org.apache.hadoop.hbase.regionserver.HStore.notifyChangedReadersObservers(HStore.java:1127)
> at
> org.apache.hadoop.hbase.regionserver.HStore.updateStorefiles(HStore.java:1106)
> at
> org.apache.hadoop.hbase.regionserver.HStore.access$600(HStore.java:130)
> at
> org.apache.hadoop.hbase.regionserver.HStore$StoreFlusherImpl.commit(HStore.java:2455)
> at
> org.apache.hadoop.hbase.regionserver.HRegion.internalFlushCacheAndCommit(HRegion.java:2519)
> at
> org.apache.hadoop.hbase.regionserver.HRegion.internalFlushcache(HRegion.java:2256)
> at
> org.apache.hadoop.hbase.regionserver.HRegion.internalFlushcache(HRegion.java:2218)
> at
> org.apache.hadoop.hbase.regionserver.HRegion.flushcache(HRegion.java:2110)
> at
> org.apache.hadoop.hbase.regionserver.HRegion.flush(HRegion.java:2036)
> 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:748)
>
> "RpcServer.FifoWFPBQ.default.handler=27,queue=0,port=16020" #65 daemon prio=5
> os_prio=0 tid=0x00007fa3e6280000 nid=0x4801 runnable [0x00007fa3bd29a000]
> java.lang.Thread.State: RUNNABLE
> at
> org.apache.hadoop.hbase.regionserver.DefaultMemStore$MemStoreScanner.getNext(DefaultMemStore.java:780)
> at
> org.apache.hadoop.hbase.regionserver.DefaultMemStore$MemStoreScanner.seekInSubLists(DefaultMemStore.java:826)
> - locked <0x00000000b45aa5b8> (a
> org.apache.hadoop.hbase.regionserver.DefaultMemStore$MemStoreScanner)
> at
> org.apache.hadoop.hbase.regionserver.DefaultMemStore$MemStoreScanner.seek(DefaultMemStore.java:818)
> - locked <0x00000000b45aa5b8> (a
> org.apache.hadoop.hbase.regionserver.DefaultMemStore$MemStoreScanner)
> at
> org.apache.hadoop.hbase.regionserver.DefaultMemStore$MemStoreScanner.seekToPreviousRow(DefaultMemStore.java:1000)
> - locked <0x00000000b45aa5b8> (a
> org.apache.hadoop.hbase.regionserver.DefaultMemStore$MemStoreScanner)
> at
> org.apache.hadoop.hbase.regionserver.ReversedKeyValueHeap.next(ReversedKeyValueHeap.java:136)
> at
> org.apache.hadoop.hbase.regionserver.*StoreScanner.next(StoreScanner.java:629)*
> at
> org.apache.hadoop.hbase.regionserver.KeyValueHeap.next(KeyValueHeap.java:147)
> at
> org.apache.hadoop.hbase.regionserver.HRegion$RegionScannerImpl.populateResult(HRegion.java:5876)
> at
> org.apache.hadoop.hbase.regionserver.HRegion$RegionScannerImpl.nextInternal(HRegion.java:6027)
> at
> org.apache.hadoop.hbase.regionserver.HRegion$RegionScannerImpl.nextRaw(HRegion.java:5814)
> at
> org.apache.hadoop.hbase.regionserver.RSRpcServices.scan(RSRpcServices.java:2552)
> - locked <0x000000009ee8ca10> (a
> org.apache.hadoop.hbase.regionserver.ReversedRegionScannerImpl)
> at
> org.apache.hadoop.hbase.protobuf.generated.ClientProtos$ClientService$2.callBlockingMethod(ClientProtos.java:32385)
> at org.apache.hadoop.hbase.ipc.RpcServer.call(RpcServer.java:2150)
> at org.apache.hadoop.hbase.ipc.CallRunner.run(CallRunner.java:112)
> at
> org.apache.hadoop.hbase.ipc.RpcExecutor$Handler.run(RpcExecutor.java:187)
> at
> org.apache.hadoop.hbase.ipc.RpcExecutor$Handler.run(RpcExecutor.java:167)
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