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From "Nick Dimiduk (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-13407) Add a configurable jitter to MemStoreFlusher#FlushHandler in order to smooth write latency
Date Wed, 08 Apr 2015 04:17:12 GMT

    [ https://issues.apache.org/jira/browse/HBASE-13407?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14484685#comment-14484685

Nick Dimiduk commented on HBASE-13407:

Nice find [~esteban]. Can you suggest any other ways we can avoid the herd of regions stampeding
a region server?

> Add a configurable jitter to MemStoreFlusher#FlushHandler in order to smooth write latency
> ------------------------------------------------------------------------------------------
>                 Key: HBASE-13407
>                 URL: https://issues.apache.org/jira/browse/HBASE-13407
>             Project: HBase
>          Issue Type: Improvement
>            Reporter: Esteban Gutierrez
>            Assignee: Esteban Gutierrez
>         Attachments: memstoreflush.png
> There is a very interesting behavior that I can reproduce consistently with many workloads
from HBase 0.98 to HBase 1.0 since hbase.hstore.flusher.count was set by default to 2: when
writes are evenly distributed across regions, memstores grow and flush about the same rate
causing spikes in IO and CPU. The side effect of those spikes is loss in throughput which
in some cases can above 10% impacting write metrics. When the flushes get a out of sync the
spikes lower and and throughput is very stable. Reverting hbase.hstore.flusher.count to 1
doesn't help too much with write heavy workloads since we end with a large flush queue that
eventually can block writers.
> Adding a small configurable jitter hbase.server.thread.wakefrequency.jitter.pct (a percentage
of the hbase.server.thread.wakefrequency frequency) can help to stagger the writes from FlushHandler
to HDFS and smooth the write latencies when the memstores are flushed in multiple threads.

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