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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-8755) A new write thread model for HLog to improve the overall HBase write throughput
Date Wed, 18 Sep 2013 15:35:52 GMT

    [ https://issues.apache.org/jira/browse/HBASE-8755?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13770888#comment-13770888
] 

stack commented on HBASE-8755:
------------------------------

Just parking the numbers here.   Takes same time to write 5x as much (5M entries by 5 threads)
as 1M entries by 1 thread.  50x takes 6x longer (50 threads writing 50M entries) 

{code}
/tmp/log-patch1.1.txt:2013-09-17 21:19:31,495 INFO  [main] wal.HLogPerformanceEvaluation:
Summary: threads=1, iterations=1000000 took 991.258s 1008.819ops/s
/tmp/log-patch1.2.txt:2013-09-17 21:35:04,715 INFO  [main] wal.HLogPerformanceEvaluation:
Summary: threads=1, iterations=1000000 took 924.881s 1081.220ops/s
/tmp/log-patch1.3.txt:2013-09-17 21:51:32,416 INFO  [main] wal.HLogPerformanceEvaluation:
Summary: threads=1, iterations=1000000 took 979.312s 1021.125ops/s
/tmp/log-patch50.1.txt:2013-09-17 23:29:45,188 INFO  [main] wal.HLogPerformanceEvaluation:
Summary: threads=50, iterations=1000000 took 2960.095s 16891.350ops/s
/tmp/log-patch50.2.txt:2013-09-18 00:22:48,849 INFO  [main] wal.HLogPerformanceEvaluation:
Summary: threads=50, iterations=1000000 took 2924.844s 17094.930ops/s
/tmp/log-patch50.3.txt:2013-09-18 01:15:58,646 INFO  [main] wal.HLogPerformanceEvaluation:
Summary: threads=50, iterations=1000000 took 2927.617s 17078.736ops/s
/tmp/log-patch5.1.txt:2013-09-17 22:07:31,712 INFO  [main] wal.HLogPerformanceEvaluation:
Summary: threads=5, iterations=1000000 took 950.968s 5257.800ops/s
/tmp/log-patch5.2.txt:2013-09-17 22:23:39,680 INFO  [main] wal.HLogPerformanceEvaluation:
Summary: threads=5, iterations=1000000 took 939.312s 5323.045ops/s
/tmp/log-patch5.3.txt:2013-09-17 22:39:56,011 INFO  [main] wal.HLogPerformanceEvaluation:
Summary: threads=5, iterations=1000000 took 947.183s 5278.811ops/s
{code}
                
> A new write thread model for HLog to improve the overall HBase write throughput
> -------------------------------------------------------------------------------
>
>                 Key: HBASE-8755
>                 URL: https://issues.apache.org/jira/browse/HBASE-8755
>             Project: HBase
>          Issue Type: Improvement
>          Components: Performance, wal
>            Reporter: Feng Honghua
>            Assignee: stack
>            Priority: Critical
>             Fix For: 0.96.1
>
>         Attachments: 8755trunkV2.txt, HBASE-8755-0.94-V0.patch, HBASE-8755-0.94-V1.patch,
HBASE-8755-trunk-V0.patch, HBASE-8755-trunk-V1.patch
>
>
> In current write model, each write handler thread (executing put()) will individually
go through a full 'append (hlog local buffer) => HLog writer append (write to hdfs) =>
HLog writer sync (sync hdfs)' cycle for each write, which incurs heavy race condition on updateLock
and flushLock.
> The only optimization where checking if current syncTillHere > txid in expectation
for other thread help write/sync its own txid to hdfs and omitting the write/sync actually
help much less than expectation.
> Three of my colleagues(Ye Hangjun / Wu Zesheng / Zhang Peng) at Xiaomi proposed a new
write thread model for writing hdfs sequence file and the prototype implementation shows a
4X improvement for throughput (from 17000 to 70000+). 
> I apply this new write thread model in HLog and the performance test in our test cluster
shows about 3X throughput improvement (from 12150 to 31520 for 1 RS, from 22000 to 70000 for
5 RS), the 1 RS write throughput (1K row-size) even beats the one of BigTable (Precolator
published in 2011 says Bigtable's write throughput then is 31002). I can provide the detailed
performance test results if anyone is interested.
> The change for new write thread model is as below:
>  1> All put handler threads append the edits to HLog's local pending buffer; (it notifies
AsyncWriter thread that there is new edits in local buffer)
>  2> All put handler threads wait in HLog.syncer() function for underlying threads
to finish the sync that contains its txid;
>  3> An single AsyncWriter thread is responsible for retrieve all the buffered edits
in HLog's local pending buffer and write to the hdfs (hlog.writer.append); (it notifies AsyncFlusher
thread that there is new writes to hdfs that needs a sync)
>  4> An single AsyncFlusher thread is responsible for issuing a sync to hdfs to persist
the writes by AsyncWriter; (it notifies the AsyncNotifier thread that sync watermark increases)
>  5> An single AsyncNotifier thread is responsible for notifying all pending put handler
threads which are waiting in the HLog.syncer() function
>  6> No LogSyncer thread any more (since there is always AsyncWriter/AsyncFlusher threads
do the same job it does)

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