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https://issues.apache.org/jira/browse/HBASE-26960?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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chenglei updated HBASE-26960:
-----------------------------
Resolution: Fixed
Status: Resolved (was: Patch Available)
> Another case for unnecessary replication suspending in RegionReplicationSink
> ----------------------------------------------------------------------------
>
> Key: HBASE-26960
> URL: https://issues.apache.org/jira/browse/HBASE-26960
> Project: HBase
> Issue Type: Bug
> Components: read replicas
> Affects Versions: 3.0.0-alpha-2
> Reporter: chenglei
> Assignee: chenglei
> Priority: Major
> Fix For: 3.0.0-alpha-3
>
>
> Besides HBASE-26768, there is another case replication in
> {{RegionReplicationSink}} would be suspend:
> For {{RegionReplicationSink}}, when there is a replication error ,
> {{RegionReplicationSink}} invokes {{MemStoreFlusher#requestFlush}} to request
> a flush, and after receiving the {{FlushAction#START_FLUSH}} or
> {{FlushAction#CANNOT_FLUSH}} flush marker, it would resume the replication.
> But when {{MemStoreFlusher}} flushing, it invokes following method
> {{HRegion.flushcache}} with the {{writeFlushRequestWalMarker}} set to false:
> {code:java}
> public FlushResultImpl flushcache(List<byte[]> families,
> boolean writeFlushRequestWalMarker, FlushLifeCycleTracker tracker)
> throws IOException {
> }
> {code}
> When {{writeFlushRequestWalMarker}} is set to false, {{HRegion.flushcache}}
> does not write the {{FlushAction#CANNOT_FLUSH}} flush marker to {{WAL}} when
> the memstore is empty, just as following
> {{HRegion.writeFlushRequestMarkerToWAL}} illustrated:
> {code:java}
> private boolean writeFlushRequestMarkerToWAL(WAL wal, boolean
> writeFlushWalMarker) {
> if (writeFlushWalMarker && wal != null && !writestate.readOnly) {
> FlushDescriptor desc =
> ProtobufUtil.toFlushDescriptor(FlushAction.CANNOT_FLUSH,
> getRegionInfo(), -1, new TreeMap<>(Bytes.BYTES_COMPARATOR));
> try {
> WALUtil.writeFlushMarker(wal, this.getReplicationScope(),
> getRegionInfo(), desc, true, mvcc,
> regionReplicationSink.orElse(null));
> return true;
> } catch (IOException e) {
> LOG.warn(getRegionInfo().getEncodedName() + " : " +
> "Received exception while trying to write the flush request to
> wal", e);
> }
> }
> return false;
> }
> {code}
> so when there is a replication error when the memstore is empty(eg.
> replicating the {{FlushAction#START_FLUSH}} or {{FlushAction#COMMIT_FLUSH}}
> ), the replication may suspend until next memstore flush,even though later
> there are user writes and it could replicate normally.
> I simulate this problem in the PR , and for {{writeFlushRequestWalMarker}}
> paramter, it is introduced by HBASE-11580 and just only determines whether or
> not writing the {{FlushAction#CANNOT_FLUSH}} flush marker to WAL when the
> memstore is empty, so I think for simplicity, we could set it to true always
> for {{MemStoreFlusher}}.
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