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https://issues.apache.org/jira/browse/HBASE-2105?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12798927#action_12798927
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stack commented on HBASE-2105:
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Yeah, I was going to say what Ryan says, that down in SequenceFile, its
synchronized anyway so we'd be narrowing the synchronization for sure but ain't
sure the narrowing would make for that much in performance improvement.
Chatting too w/ J-D, we probably want the current synchronization to ensure
that the get of the next sequence number happens in the same synchronization
block that does the actual write. Otherwise, we could have edits going in out
of order which could be a prob. if a high number edit goes in before a lower
number edit.... we might lose a few edits if we crash after the high number
goes in but before the lower edits have a chance to go in.
We might want to revisit if we want to run a pool of WAL-writers.
> All appends are serialized in HLog
> ----------------------------------
>
> Key: HBASE-2105
> URL: https://issues.apache.org/jira/browse/HBASE-2105
> Project: Hadoop HBase
> Issue Type: Bug
> Affects Versions: 0.20.2
> Reporter: Jean-Daniel Cryans
> Assignee: Jean-Daniel Cryans
> Priority: Blocker
> Fix For: 0.20.4, 0.21.0
>
>
> duiod on IRC was asking about locks on the write path so I reviewed it a bit
> and saw that we are very good at not locking except on row level in HRegion
> and others but in HLog we actually synchronize everything on updateLock. I'm
> pretty sure that's not what we want. I guess a RWLock would be more useful.
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