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Lars Hofhansl commented on HBASE-15392: --------------------------------------- +1 on -v6. Minor spelling nit in comment: {{It does this looking at the next}}, missed a "by". > 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, 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. -- This 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