[jira] [Commented] (HBASE-3719) Workload has to drain before hlog can be rolled

["Sean Busbey (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-3719?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14261284#comment-14261284 ] 

Sean Busbey commented on HBASE-3719:
------------------------------------

client request to those regions that share the WAL that is rolling will wait, yes. I don't think we actually need to wait for the log close though, provided we had waited for a sync (that is, our persistence promise is already met at sync time).

One of the suggestions I've seen in connection with HBASE-10278 is to always use a hot spare HDFS pipeline to do the rolling. I think that's a great idea and we could combine it with having a worker handle the closing outside of the critical section. That should go a long way to minimizing how much of a time hit clients take at roll time.

> Workload has to drain before hlog can be rolled
> -----------------------------------------------
>
>                 Key: HBASE-3719
>                 URL: https://issues.apache.org/jira/browse/HBASE-3719
>             Project: HBase
>          Issue Type: Improvement
>          Components: regionserver, wal
>            Reporter: dhruba borthakur
>            Assignee: dhruba borthakur
>
> In the current implementation, the regionserver blocks new transactions from occuring when the HLog is rolled. Closing the existing HLog sometimes takes more than a few seconds and during this time all new puts/increments are blocked. It will be nice if we can continue to write new transactions to the new HLog (but maybe not commit those transactions) while the old HLog is being closed.



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