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https://issues.apache.org/jira/browse/HBASE-23591?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17011417#comment-17011417
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Anoop Sam John commented on HBASE-23591:
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So in ur proposal u r adding a catch (Exception ex) and handling the
decrMemStoreSize correctly in try. The replayFlushInStores might get exception
and so closing and clearing of the snapshot would not have happened then. We
will still keep the snapshot at Memstore level. Then when the subsequent
flushes happen on the same CFs and replay WAL marker reaches the replica
regions how that will get handled? The begin flush marker will not be able to
take snapshot as there is already a snapshot present.
> Negative memStoreSizing
> -----------------------
>
> Key: HBASE-23591
> URL: https://issues.apache.org/jira/browse/HBASE-23591
> Project: HBase
> Issue Type: Bug
> Components: read replicas
> Reporter: Szabolcs Bukros
> Priority: Major
> Fix For: 2.2.2
>
>
> After a flush on the replica region the memStoreSizing becomes negative:
> {code:java}
> 2019-12-17 08:31:59,983 DEBUG org.apache.hadoop.hbase.regionserver.HRegion:
> 0beaae111b0f6e98bfde31ba35be5408 : Replaying flush marker action:
> COMMIT_FLUSH table_name: "IntegrationTestRegionReplicaReplicati
> on" encoded_region_name: "544affde3e027454f67c8ea46c8f69ee"
> flush_sequence_number: 41392 store_flushes { family_name: "f1"
> store_home_dir: "f1" flush_output: "3c48a23eac784a348a18e10e337d80a2" }
> store_flushes { family_name: "f2" store_home_dir: "f2" flush_output:
> "9a5283ec95694667b4ead2398af5f01e" } store_flushes { family_name: "f3"
> store_home_dir: "f3" flush_output: "e6f25e6b0eca4d22af15d0626d0f8759" }
> region_name:
> "IntegrationTestRegionReplicaReplication,bbbbbbbb,1576599911697.544affde3e027454f67c8ea46c8f69ee."
> 2019-12-17 08:31:59,984 DEBUG org.apache.hadoop.hbase.regionserver.HRegion:
> 0beaae111b0f6e98bfde31ba35be5408 : Received a flush commit marker with
> seqId:41392 and a previous prepared snapshot was found
> 2019-12-17 08:31:59,993 INFO org.apache.hadoop.hbase.regionserver.HStore:
> Region: 0beaae111b0f6e98bfde31ba35be5408 added
> hdfs://replica-1:8020/hbase/data/default/IntegrationTestRegionReplicaReplication/544affde3e027454f67c8ea46c8f69ee/f1/3c48a23eac784a348a18e10e337d80a2,
> entries=32445, sequenceid=41392, filesize=27.6 M
> 2019-12-17 08:32:00,016 INFO org.apache.hadoop.hbase.regionserver.HStore:
> Region: 0beaae111b0f6e98bfde31ba35be5408 added
> hdfs://replica-1:8020/hbase/data/default/IntegrationTestRegionReplicaReplication/544affde3e027454f67c8ea46c8f69ee/f2/9a5283ec95694667b4ead2398af5f01e,
> entries=12264, sequenceid=41392, filesize=10.9 M
> 2019-12-17 08:32:00,121 INFO org.apache.hadoop.hbase.regionserver.HStore:
> Region: 0beaae111b0f6e98bfde31ba35be5408 added
> hdfs://replica-1:8020/hbase/data/default/IntegrationTestRegionReplicaReplication/544affde3e027454f67c8ea46c8f69ee/f3/e6f25e6b0eca4d22af15d0626d0f8759,
> entries=32379, sequenceid=41392, filesize=27.5 M
> 2019-12-17 08:32:00,122 DEBUG org.apache.hadoop.hbase.regionserver.HRegion:
> CustomLog decrMemStoreSize. Current: dataSize=135810071,
> getHeapSize=148400960, getOffHeapSize=0, getCellsCount=167243 delta:
> dataSizeDelta=155923644, heapSizeDelta=170112320, offHeapSizeDelta=0,
> cellsCountDelta=188399
> 2019-12-17 08:32:00,122 ERROR org.apache.hadoop.hbase.regionserver.HRegion:
> Asked to modify this region's
> (IntegrationTestRegionReplicaReplication,bbbbbbbb,1576599911697_0001.0beaae111b0f6e98bfde31ba35be54
> 08.) memStoreSizing to a negative value which is incorrect. Current
> memStoreSizing=135810071, delta=-155923644
> java.lang.Exception
> at
> org.apache.hadoop.hbase.regionserver.HRegion.checkNegativeMemStoreDataSize(HRegion.java:1323)
> at
> org.apache.hadoop.hbase.regionserver.HRegion.decrMemStoreSize(HRegion.java:1316)
> at
> org.apache.hadoop.hbase.regionserver.HRegion.decrMemStoreSize(HRegion.java:1303)
> at
> org.apache.hadoop.hbase.regionserver.HRegion.replayWALFlushCommitMarker(HRegion.java:5194)
> at
> org.apache.hadoop.hbase.regionserver.HRegion.replayWALFlushMarker(HRegion.java:5025)
> at
> org.apache.hadoop.hbase.regionserver.RSRpcServices.doReplayBatchOp(RSRpcServices.java:1143)
> at
> org.apache.hadoop.hbase.regionserver.RSRpcServices.replay(RSRpcServices.java:2232)
> at
> org.apache.hadoop.hbase.shaded.protobuf.generated.AdminProtos$AdminService$2.callBlockingMethod(AdminProtos.java:29754)
> at org.apache.hadoop.hbase.ipc.RpcServer.call(RpcServer.java:413)
> at org.apache.hadoop.hbase.ipc.CallRunner.run(CallRunner.java:133)
> at
> org.apache.hadoop.hbase.ipc.RpcExecutor$Handler.run(RpcExecutor.java:338)
> at
> org.apache.hadoop.hbase.ipc.RpcExecutor$Handler.run(RpcExecutor.java:318)
> {code}
> I added some custom logging to the snapshot logic to be able to see snapshot
> sizes:
> {code:java}
> 2019-12-17 08:31:56,900 DEBUG org.apache.hadoop.hbase.regionserver.HRegion:
> 0beaae111b0f6e98bfde31ba35be5408 : Replaying flush marker action: START_FLUSH
> table_name: "IntegrationTestRegionReplicaReplication" encoded_region_name:
> "544affde3e027454f67c8ea46c8f69ee" flush_sequence_number: 41392 store_flushes
> { family_name: "f1" store_home_dir: "f1" } store_flushes { family_name: "f2"
> store_home_dir: "f2" } store_flushes { family_name: "f3" store_home_dir: "f3"
> } region_name:
> "IntegrationTestRegionReplicaReplication,bbbbbbbb,1576599911697.544affde3e027454f67c8ea46c8f69ee."
> 2019-12-17 08:31:56,900 INFO org.apache.hadoop.hbase.regionserver.HRegion:
> Flushing 0beaae111b0f6e98bfde31ba35be5408 3/3 column families,
> dataSize=126.49 MB heapSize=138.24 MB
> 2019-12-17 08:31:56,900 WARN
> org.apache.hadoop.hbase.regionserver.DefaultMemStore: Snapshot called again
> without clearing previous. Doing nothing. Another ongoing flush or did we
> fail last attempt?
> 2019-12-17 08:31:56,900 DEBUG
> org.apache.hadoop.hbase.regionserver.DefaultMemStore: CustomLog snapshot for
> region: {ENCODED => 0beaae111b0f6e98bfde31ba35be5408, NAME =>
> 'IntegrationTestRegionReplicaReplication,bbbbbbbb,1576599911697_0001.0beaae111b0f6e98bfde31ba35be5408.',
> STARTKEY => 'bbbbbbbb', ENDKEY => 'cccccccc', REPLICA_ID => 1} memstore:
> dataSize=41660529, getHeapSize=45422304, getOffHeapSize=0, getCellsCount=49951
> 2019-12-17 08:31:56,901 DEBUG
> org.apache.hadoop.hbase.regionserver.DefaultMemStore: CustomLog snapshot for
> region: {ENCODED => 0beaae111b0f6e98bfde31ba35be5408, NAME =>
> 'IntegrationTestRegionReplicaReplication,bbbbbbbb,1576599911697_0001.0beaae111b0f6e98bfde31ba35be5408.',
> STARTKEY => 'bbbbbbbb', ENDKEY => 'cccccccc', REPLICA_ID => 1} memstore:
> dataSize=72246315, getHeapSize=78890240, getOffHeapSize=0, getCellsCount=88222
> 2019-12-17 08:31:56,901 WARN
> org.apache.hadoop.hbase.regionserver.DefaultMemStore: Snapshot called again
> without clearing previous. Doing nothing. Another ongoing flush or did we
> fail last attempt?
> 2019-12-17 08:31:56,901 DEBUG
> org.apache.hadoop.hbase.regionserver.DefaultMemStore: CustomLog snapshot for
> region: {ENCODED => 0beaae111b0f6e98bfde31ba35be5408, NAME =>
> 'IntegrationTestRegionReplicaReplication,bbbbbbbb,1576599911697_0001.0beaae111b0f6e98bfde31ba35be5408.',
> STARTKEY => 'bbbbbbbb', ENDKEY => 'cccccccc', REPLICA_ID => 1} memstore:
> dataSize=42016800, getHeapSize=45799776, getOffHeapSize=0, getCellsCount=50226
> 2019-12-17 08:31:56,901 DEBUG org.apache.hadoop.hbase.regionserver.HRegion:
> 0beaae111b0f6e98bfde31ba35be5408 : Prepared flush with seqId:41392
> {code}
> This shows that snapshots combined size is actually bigger than the region's
> memStoreSizing. So when do we decrease memStoreSizing without actually
> flushing?
> A bit earlier in the log I found this:
> {code:java}
> 2019-12-17 08:31:43,581 DEBUG org.apache.hadoop.hbase.regionserver.HRegion:
> 0beaae111b0f6e98bfde31ba35be5408 : Replaying flush marker action: START_FLUSH
> table_name: "IntegrationTestRegionReplicaReplication" encoded_region_name:
> "544affde3e027454f67c8ea46c8f69ee" flush_sequence_number: 40445 store_flushes
> { family_name: "f2" store_home_dir: "f2" } region_name:
> "IntegrationTestRegionReplicaReplication,bbbbbb
> bb,1576599911697.544affde3e027454f67c8ea46c8f69ee."
> 2019-12-17 08:31:43,582 WARN org.apache.hadoop.hbase.regionserver.HRegion:
> 0beaae111b0f6e98bfde31ba35be5408 : Received a flush prepare marker with a
> larger seqId: 40445 before clearing the previous one with seqId: 20747.
> Ignoring
> 2019-12-17 08:31:43,582 TRACE org.apache.hadoop.hbase.regionserver.HRegion:
> 0beaae111b0f6e98bfde31ba35be5408 : Store files for region:
> 2019-12-17 08:31:43,582 INFO org.apache.hadoop.hbase.regionserver.HRegion:
> writing data to region
> IntegrationTestRegionReplicaReplication,bbbbbbbb,1576599911697_0001.0beaae111b0f6e98bfde31ba35be5408.
> with WAL disabled. Data may be lost in the event of a crash.
> 2019-12-17 08:31:43,586 DEBUG org.apache.hadoop.hbase.regionserver.HRegion:
> 0beaae111b0f6e98bfde31ba35be5408 : Replaying flush marker action:
> COMMIT_FLUSH table_name: "IntegrationTestRegionReplicaReplication"
> encoded_region_name: "544affde3e027454f67c8ea46c8f69ee"
> flush_sequence_number: 40445 store_flushes { family_name: "f2"
> store_home_dir: "f2" flush_output: "3f6a5302b36a4a65a6caa291a03f108d" }
> region_name:
> "IntegrationTestRegionReplicaReplication,bbbbbbbb,1576599911697.544affde3e027454f67c8ea46c8f69ee."
> 2019-12-17 08:31:43,586 WARN org.apache.hadoop.hbase.regionserver.HRegion:
> 0beaae111b0f6e98bfde31ba35be5408 : Received a flush commit marker with larger
> seqId: 40445 than what we have prepared with seqId:
> 20747. Picking up new file and dropping prepared memstore snapshot
> 2019-12-17 08:31:43,587 WARN org.apache.hadoop.hbase.regionserver.HRegion:
> 0beaae111b0f6e98bfde31ba35be5408 : Unexpected: flush commit marker received
> from store f2 but no associated flush context. Ignoring
> 2019-12-17 08:31:43,587 DEBUG org.apache.hadoop.hbase.regionserver.HRegion:
> CustomLog decrMemStoreSize. Current: dataSize=184492444,
> getHeapSize=201769960, getOffHeapSize=0, getCellsCount=229450 delta:
> dataSizeDelta=83677329, heapSizeDelta=91222080, offHeapSizeDelta=0,
> cellsCountDelta=100177
> 2019-12-17 08:31:43,587 INFO org.apache.hadoop.hbase.regionserver.HRegion:
> 0beaae111b0f6e98bfde31ba35be5408 : Not dropping memstore contents since
> replayed flush seqId: 40445 is smaller than current seqId:40481
> {code}
> Based on this the issues seems to originate from HRegion.replayFlushInStores.
> The StoreFlushContext is missing, we show a warning and continue the
> execution with the next StoreFlushDescriptor without actually flushing the
> snapshot in question. However replayWALFlushCommitMarker is unaware of the
> warn and continues assuming the flush was successful and decreasing the
> memStoreSizing (and doing cleanup).
>
> We should consider decreasing the memStoreSizing on a per store level instead
> of on the region level and do the negativity check before we do it,
> potentially preventing a flush if needed, to make sure we keep the
> memStoreSizing positive.
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