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https://issues.apache.org/jira/browse/HBASE-3322?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jonathan Gray resolved HBASE-3322.
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Resolution: Won't Fix
There is an issue here but upon further investigation, it's not really a bug.
The issue is around heavy concurrency / high number of threads in HLog. The
current behavior is that each thread does a notify to the LogSyncer and then
does a wait on a single object. The LogSyncer waits to be notified, then syncs
what is pending, and then does a notifyAll to all the threads waiting for their
sync.
This is a straightforward and correct pattern but under heavy concurrency, the
fact that all threads are waiting on a single object to be notified becomes a
bottleneck.
Will open other JIRAs to deal with solutions to this. Closing this one as this
is not a blocking bug.
> HLog sync slowdown under heavy load with HBASE-2467
> ---------------------------------------------------
>
> Key: HBASE-3322
> URL: https://issues.apache.org/jira/browse/HBASE-3322
> Project: HBase
> Issue Type: Bug
> Components: io, regionserver
> Affects Versions: 0.90.0
> Reporter: Jonathan Gray
> Priority: Blocker
> Fix For: 0.92.0
>
>
> Testing HBASE-2467 and HDFS-895 on 100 node cluster w/ a heavy increment
> workload we experienced significant slowdown.
> Stack traces show that most threads are on HLog.updateLock.
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