[jira] [Created] (HBASE-13407) Add a configurable jitter to MemStoreFlusher#FlushHandler in order to smooth write latency

["Esteban Gutierrez (JIRA)" <ji...@apache.org>]

Esteban Gutierrez created HBASE-13407:
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             Summary: 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


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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