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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HBASE-15392) Single Cell Get reads two HFileBlocks
Date Mon, 14 Mar 2016 19:01:33 GMT

     [ https://issues.apache.org/jira/browse/HBASE-15392?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

stack updated HBASE-15392:
--------------------------
    Release Note: 
When an explicit Get with a one or more columns specified, we at a minimum, were overseeking,
reading until we tripped over the next row, regardless, and only then returning. If the next
row was in-block, we'd just do too much seeking but if the next row was in the next (or in
the next block beyond that), we would keep seeking and loading blocks until we found the next
row before we'd return.

There remains one case where we will still 'overread'. It is when the row end aligns with
the end of the block. In this case we will load the next block just to find that there are
no more cells in the current row. See HBASE-15457.

  was:When an explicit Get with a one or more columns specified, we at a minimum, were overseeking
reading until we tripped over the next row, regardless, and only then returning. If the next
row was in-block, we'd just do too much seeking but if the next row is in the next (or in
the next block beyond that), we will keep seeking and loading blocks until we find the next
row before we'd return.


> Single Cell Get reads two HFileBlocks
> -------------------------------------
>
>                 Key: HBASE-15392
>                 URL: https://issues.apache.org/jira/browse/HBASE-15392
>             Project: HBase
>          Issue Type: Sub-task
>          Components: BucketCache
>            Reporter: stack
>            Assignee: stack
>         Attachments: 15392-0.98-looksee.txt, 15392.wip.patch, 15392v2.wip.patch, 15392v3.wip.patch,
15392v4.patch, 15392v5.patch, 15392v6.patch, 15392v7.patch, 15392v7.patch, 15392v7.patch,
15392v7.patch, HBASE-15392_suggest.patch, gc.png, gc.png, io.png, no_optimize.patch, no_optimize.patch,
reads.png, reads.png, two_seeks.txt
>
>
> As found by Daniel "SystemTap" Pol, a simple Get results in our reading two HFileBlocks,
the one that contains the wanted Cell, and the block that follows.
> Here is a bit of custom logging that logs a stack trace on each HFileBlock read so you
can see the call stack responsible:
> {code}
> 2016-03-03 22:20:30,191 INFO  [B.defaultRpcServer.handler=20,queue=2,port=16020] regionserver.StoreScanner:
START LOOP
> 2016-03-03 22:20:30,192 INFO  [B.defaultRpcServer.handler=20,queue=2,port=16020] regionserver.StoreScanner:
QCODE SEEK_NEXT_COL
> 2016-03-03 22:20:30,192 INFO  [B.defaultRpcServer.handler=20,queue=2,port=16020] hfile.HFileBlockIndex:
STARTED WHILE
> 2016-03-03 22:20:30,192 INFO  [B.defaultRpcServer.handler=20,queue=2,port=16020] hfile.CombinedBlockCache:
OUT OF L2
> 2016-03-03 22:20:30,192 TRACE [B.defaultRpcServer.handler=20,queue=2,port=16020] bucket.BucketCache:
Read offset=31409152, len=2103
> 2016-03-03 22:20:30,192 TRACE [B.defaultRpcServer.handler=20,queue=2,port=16020] bucket.FileIOEngine:
offset=31409152, length=2103
> 2016-03-03 22:20:30,193 TRACE [B.defaultRpcServer.handler=20,queue=2,port=16020] hfile.HFileReaderImpl:
From Cache [blockType=DATA, fileOffset=2055421, headerSize=33, onDiskSizeWithoutHeader=2024,
uncompressedSizeWithoutHeader=2020, prevBlockOffset=2053364, isUseHBaseChecksum=true, checksumType=CRC32C,
bytesPerChecksum=16384, onDiskDataSizeWithHeader=2053, getOnDiskSizeWithHeader=2057, totalChecksumBytes=4,
isUnpacked=true, buf=[org.apache.hadoop.hbase.nio.SingleByteBuff@e19fbd54], dataBeginsWith=\x00\x00\x00)\x00\x00\x01`\x00\x16user995139035672819231,
fileContext=[usesHBaseChecksum=true, checksumType=CRC32C, bytesPerChecksum=16384, blocksize=65536,
encoding=NONE, includesMvcc=true, includesTags=false, compressAlgo=NONE, compressTags=false,
cryptoContext=[cipher=NONE keyHash=NONE]]]
> 2016-03-03 22:20:30,193 TRACE [B.defaultRpcServer.handler=20,queue=2,port=16020] hfile.HFileReaderImpl:
Cache hit return [blockType=DATA, fileOffset=2055421, headerSize=33, onDiskSizeWithoutHeader=2024,
uncompressedSizeWithoutHeader=2020, prevBlockOffset=2053364, isUseHBaseChecksum=true, checksumType=CRC32C,
bytesPerChecksum=16384, onDiskDataSizeWithHeader=2053, getOnDiskSizeWithHeader=2057, totalChecksumBytes=4,
isUnpacked=true, buf=[org.apache.hadoop.hbase.nio.SingleByteBuff@e19fbd54], dataBeginsWith=\x00\x00\x00)\x00\x00\x01`\x00\x16user995139035672819231,
fileContext=[usesHBaseChecksum=true, checksumType=CRC32C, bytesPerChecksum=16384, blocksize=65536,
encoding=NONE, includesMvcc=true, includesTags=false, compressAlgo=NONE, compressTags=false,
cryptoContext=[cipher=NONE keyHash=NONE]]]
> java.lang.Throwable
>         at org.apache.hadoop.hbase.io.hfile.HFileReaderImpl.readBlock(HFileReaderImpl.java:1515)
>         at org.apache.hadoop.hbase.io.hfile.HFileBlockIndex$CellBasedKeyBlockIndexReader.loadDataBlockWithScanInfo(HFileBlockIndex.java:324)
>         at org.apache.hadoop.hbase.io.hfile.HFileReaderImpl$HFileScannerImpl.seekTo(HFileReaderImpl.java:831)
>         at org.apache.hadoop.hbase.io.hfile.HFileReaderImpl$HFileScannerImpl.reseekTo(HFileReaderImpl.java:812)
>         at org.apache.hadoop.hbase.regionserver.StoreFileScanner.reseekAtOrAfter(StoreFileScanner.java:288)
>         at org.apache.hadoop.hbase.regionserver.StoreFileScanner.reseek(StoreFileScanner.java:198)
>         at org.apache.hadoop.hbase.regionserver.NonLazyKeyValueScanner.doRealSeek(NonLazyKeyValueScanner.java:54)
>         at org.apache.hadoop.hbase.regionserver.KeyValueHeap.generalizedSeek(KeyValueHeap.java:321)
>         at org.apache.hadoop.hbase.regionserver.KeyValueHeap.requestSeek(KeyValueHeap.java:279)
>         at org.apache.hadoop.hbase.regionserver.StoreScanner.reseek(StoreScanner.java:806)
>         at org.apache.hadoop.hbase.regionserver.StoreScanner.seekAsDirection(StoreScanner.java:795)
>         at org.apache.hadoop.hbase.regionserver.StoreScanner.next(StoreScanner.java:624)
>         at org.apache.hadoop.hbase.regionserver.KeyValueHeap.next(KeyValueHeap.java:153)
>         at org.apache.hadoop.hbase.regionserver.HRegion$RegionScannerImpl.populateResult(HRegion.java:5703)
>         at org.apache.hadoop.hbase.regionserver.HRegion$RegionScannerImpl.nextInternal(HRegion.java:5849)
>         at org.apache.hadoop.hbase.regionserver.HRegion$RegionScannerImpl.nextRaw(HRegion.java:5622)
>         at org.apache.hadoop.hbase.regionserver.HRegion$RegionScannerImpl.next(HRegion.java:5598)
>         at org.apache.hadoop.hbase.regionserver.HRegion$RegionScannerImpl.next(HRegion.java:5584)
>         at org.apache.hadoop.hbase.regionserver.RSRpcServices.get(RSRpcServices.java:2187)
>         at org.apache.hadoop.hbase.regionserver.RSRpcServices.get(RSRpcServices.java:2123)
>         at org.apache.hadoop.hbase.protobuf.generated.ClientProtos$ClientService$2.callBlockingMethod(ClientProtos.java:33512)
>         at org.apache.hadoop.hbase.ipc.RpcServer.call(RpcServer.java:2229)
>         at org.apache.hadoop.hbase.ipc.CallRunner.run(CallRunner.java:109)
>         at org.apache.hadoop.hbase.ipc.RpcExecutor.consumerLoop(RpcExecutor.java:136)
>         at org.apache.hadoop.hbase.ipc.RpcExecutor$1.run(RpcExecutor.java:111)
>         at java.lang.Thread.run(Thread.java:745)
> 2016-03-03 22:20:30,193 INFO  [B.defaultRpcServer.handler=20,queue=2,port=16020] hfile.HFileBlockIndex:
READ [blockType=DATA, fileOffset=2055421, headerSize=33, onDiskSizeWithoutHeader=2024, uncompressedSizeWithoutHeader=2020,
prevBlockOffset=2053364, isUseHBaseChecksum=true, checksumType=CRC32C, bytesPerChecksum=16384,
onDiskDataSizeWithHeader=2053, getOnDiskSizeWithHeader=2057, totalChecksumBytes=4, isUnpacked=true,
buf=[org.apache.hadoop.hbase.nio.SingleByteBuff@e19fbd54], dataBeginsWith=\x00\x00\x00)\x00\x00\x01`\x00\x16user995139035672819231,
fileContext=[usesHBaseChecksum=true, checksumType=CRC32C, bytesPerChecksum=16384, blocksize=65536,
encoding=NONE, includesMvcc=true, includesTags=false, compressAlgo=NONE, compressTags=false,
cryptoContext=[cipher=NONE keyHash=NONE]]]
> 2016-03-03 22:20:30,193 INFO  [B.defaultRpcServer.handler=20,queue=2,port=16020] hfile.HFileBlockIndex:
DATA BLOCK IS TRUE BREAK
> 2016-03-03 22:20:30,193 INFO  [B.defaultRpcServer.handler=20,queue=2,port=16020] hfile.HFileBlockIndex:
RETURNING
> 2016-03-03 22:20:30,194 INFO  [B.defaultRpcServer.handler=20,queue=2,port=16020] regionserver.StoreScanner:
QCODE INCLUDE
> 2016-03-03 22:20:30,194 INFO  [B.defaultRpcServer.handler=20,queue=2,port=16020] regionserver.StoreScanner:
QCODE SKIP
> 2016-03-03 22:20:30,194 INFO  [B.defaultRpcServer.handler=20,queue=2,port=16020] hfile.CombinedBlockCache:
OUT OF L2
> 2016-03-03 22:20:30,194 TRACE [B.defaultRpcServer.handler=20,queue=2,port=16020] bucket.BucketCache:
Read offset=30932992, len=2103
> 2016-03-03 22:20:30,194 TRACE [B.defaultRpcServer.handler=20,queue=2,port=16020] bucket.FileIOEngine:
offset=30932992, length=2103
> 2016-03-03 22:20:30,194 TRACE [B.defaultRpcServer.handler=20,queue=2,port=16020] hfile.HFileReaderImpl:
From Cache [blockType=DATA, fileOffset=2057478, headerSize=33, onDiskSizeWithoutHeader=2024,
uncompressedSizeWithoutHeader=2020, prevBlockOffset=2055421, isUseHBaseChecksum=true, checksumType=CRC32C,
bytesPerChecksum=16384, onDiskDataSizeWithHeader=2053, getOnDiskSizeWithHeader=2057, totalChecksumBytes=4,
isUnpacked=true, buf=[org.apache.hadoop.hbase.nio.SingleByteBuff@6063ac95], dataBeginsWith=\x00\x00\x00)\x00\x00\x01`\x00\x16user995698996184959679,
fileContext=[usesHBaseChecksum=true, checksumType=CRC32C, bytesPerChecksum=16384, blocksize=65536,
encoding=NONE, includesMvcc=true, includesTags=false, compressAlgo=NONE, compressTags=false,
cryptoContext=[cipher=NONE keyHash=NONE]]]
> 2016-03-03 22:20:30,194 TRACE [B.defaultRpcServer.handler=20,queue=2,port=16020] hfile.HFileReaderImpl:
Cache hit return [blockType=DATA, fileOffset=2057478, headerSize=33, onDiskSizeWithoutHeader=2024,
uncompressedSizeWithoutHeader=2020, prevBlockOffset=2055421, isUseHBaseChecksum=true, checksumType=CRC32C,
bytesPerChecksum=16384, onDiskDataSizeWithHeader=2053, getOnDiskSizeWithHeader=2057, totalChecksumBytes=4,
isUnpacked=true, buf=[org.apache.hadoop.hbase.nio.SingleByteBuff@6063ac95], dataBeginsWith=\x00\x00\x00)\x00\x00\x01`\x00\x16user995698996184959679,
fileContext=[usesHBaseChecksum=true, checksumType=CRC32C, bytesPerChecksum=16384, blocksize=65536,
encoding=NONE, includesMvcc=true, includesTags=false, compressAlgo=NONE, compressTags=false,
cryptoContext=[cipher=NONE keyHash=NONE]]]
> java.lang.Throwable
>         at org.apache.hadoop.hbase.io.hfile.HFileReaderImpl.readBlock(HFileReaderImpl.java:1515)
>         at org.apache.hadoop.hbase.io.hfile.HFileReaderImpl$HFileScannerImpl.readNextDataBlock(HFileReaderImpl.java:906)
>         at org.apache.hadoop.hbase.io.hfile.HFileReaderImpl$HFileScannerImpl.isNextBlock(HFileReaderImpl.java:1106)
>         at org.apache.hadoop.hbase.io.hfile.HFileReaderImpl$HFileScannerImpl.positionForNextBlock(HFileReaderImpl.java:1100)
>         at org.apache.hadoop.hbase.io.hfile.HFileReaderImpl$HFileScannerImpl._next(HFileReaderImpl.java:1118)
>         at org.apache.hadoop.hbase.io.hfile.HFileReaderImpl$HFileScannerImpl.next(HFileReaderImpl.java:1139)
>         at org.apache.hadoop.hbase.regionserver.StoreFileScanner.next(StoreFileScanner.java:152)
>         at org.apache.hadoop.hbase.regionserver.KeyValueHeap.next(KeyValueHeap.java:114)
>         at org.apache.hadoop.hbase.regionserver.StoreScanner.next(StoreScanner.java:628)
>         at org.apache.hadoop.hbase.regionserver.KeyValueHeap.next(KeyValueHeap.java:153)
>         at org.apache.hadoop.hbase.regionserver.HRegion$RegionScannerImpl.populateResult(HRegion.java:5703)
>         at org.apache.hadoop.hbase.regionserver.HRegion$RegionScannerImpl.nextInternal(HRegion.java:5849)
>         at org.apache.hadoop.hbase.regionserver.HRegion$RegionScannerImpl.nextRaw(HRegion.java:5622)
>         at org.apache.hadoop.hbase.regionserver.HRegion$RegionScannerImpl.next(HRegion.java:5598)
>         at org.apache.hadoop.hbase.regionserver.HRegion$RegionScannerImpl.next(HRegion.java:5584)
>         at org.apache.hadoop.hbase.regionserver.RSRpcServices.get(RSRpcServices.java:2187)
>         at org.apache.hadoop.hbase.regionserver.RSRpcServices.get(RSRpcServices.java:2123)
>         at org.apache.hadoop.hbase.protobuf.generated.ClientProtos$ClientService$2.callBlockingMethod(ClientProtos.java:33512)
>         at org.apache.hadoop.hbase.ipc.RpcServer.call(RpcServer.java:2229)
>         at org.apache.hadoop.hbase.ipc.CallRunner.run(CallRunner.java:109)
>         at org.apache.hadoop.hbase.ipc.RpcExecutor.consumerLoop(RpcExecutor.java:136)
>         at org.apache.hadoop.hbase.ipc.RpcExecutor$1.run(RpcExecutor.java:111)
>         at java.lang.Thread.run(Thread.java:745)
> 2016-03-03 22:20:30,195 INFO  [B.defaultRpcServer.handler=20,queue=2,port=16020] regionserver.StoreScanner:
QCODE DONE
> {code}
> We are in StoreScanner#next.
> Matcher does SEEK_NEXT_COL.
> We pull in the block that has our Cell in it.
> Matcher does INCLUDE
> Then Matcher does SKIP
> SKIP has us go read the next block.
> Then Matcher does DONE.
> Why ain't I getting to DONE after INCLUDE?
> Any clues?
> This code has been like this a while.



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