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From "Andrew Purtell (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-12424) Finer grained logging and metrics for split transactions
Date Tue, 04 Nov 2014 18:14:34 GMT

    [ https://issues.apache.org/jira/browse/HBASE-12424?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14196495#comment-14196495

Andrew Purtell commented on HBASE-12424:

We keep an in memory journal of actions taken during the split transaction. We could dump
the journal to the log when the split transaction completes (or fails). And/or we could emit
more logging at INFO level out of SplitRequest and SplitTransaction. We should also consider
exposing some of this information as metrics.

> Finer grained logging and metrics for split transactions
> --------------------------------------------------------
>                 Key: HBASE-12424
>                 URL: https://issues.apache.org/jira/browse/HBASE-12424
>             Project: HBase
>          Issue Type: Improvement
>            Reporter: Andrew Purtell
>             Fix For: 2.0.0, 0.98.8, 0.99.2
>         Attachments: HowHBaseRegionSplitsareImplemented.pdf
> A split transaction is a complex orchestration of activity between the RegionServer,
Master, ZooKeeper, and HDFS NameNode. We have some visibility into the time taken by various
phases of the split transaction in the logs. We will see "Starting split of region $PARENT"
before the transaction begins, before the parent is offlined. Later we will see "Opening $DAUGHTER"
as one of the last steps in the transaction, this is after the parent has been flushed, offlined,
and closed. Finally ""Region split, hbase:meta updated, and report to master ... Split took
$TIME" after all steps are complete and including the total running time of the transaction.

> For debugging the cause(s) of long running split transactions it would be useful to know
the distribution of time spent in all of the phases of the split transaction. 

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