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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 Thu, 12 Dec 2013 06:19:15 GMT

    [ https://issues.apache.org/jira/browse/HBASE-8755?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13846090#comment-13846090
] 

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

Pardon me. This is taking a while; hardware issues and now I trunk seems to have issue where
it hangs syncing, pre-patch I believe... investigating.

Here is what I see. Lots of threads BLOCKED here:
{code}
"RpcServer.handler=0,port=60020" daemon prio=10 tid=0x00000000012f1800 nid=0x3cb5 waiting
for monitor entry [0x00007fdb0eb55000]
   java.lang.Thread.State: BLOCKED (on object monitor)
        at org.apache.hadoop.hbase.regionserver.wal.FSHLog.append(FSHLog.java:1006)
        - waiting to lock <0x0000000456c00390> (a java.lang.Object)
        at org.apache.hadoop.hbase.regionserver.wal.FSHLog.appendNoSync(FSHLog.java:1054)
        at org.apache.hadoop.hbase.regionserver.HRegion.doMiniBatchMutation(HRegion.java:2369)
        at org.apache.hadoop.hbase.regionserver.HRegion.batchMutate(HRegion.java:2087)
        at org.apache.hadoop.hbase.regionserver.HRegion.batchMutate(HRegion.java:2037)
        at org.apache.hadoop.hbase.regionserver.HRegion.batchMutate(HRegion.java:2041)
        at org.apache.hadoop.hbase.regionserver.HRegionServer.doBatchOp(HRegionServer.java:4175)
        at org.apache.hadoop.hbase.regionserver.HRegionServer.doNonAtomicRegionMutation(HRegionServer.java:3424)
        at org.apache.hadoop.hbase.regionserver.HRegionServer.multi(HRegionServer.java:3328)
        at org.apache.hadoop.hbase.protobuf.generated.ClientProtos$ClientService$2.callBlockingMethod(ClientProtos.java:28460)
        at org.apache.hadoop.hbase.ipc.RpcServer.call(RpcServer.java:2008)
        at org.apache.hadoop.hbase.ipc.CallRunner.run(CallRunner.java:92)
        at org.apache.hadoop.hbase.ipc.SimpleRpcScheduler.consumerLoop(SimpleRpcScheduler.java:160)
        at org.apache.hadoop.hbase.ipc.SimpleRpcScheduler.access$000(SimpleRpcScheduler.java:38)
        at org.apache.hadoop.hbase.ipc.SimpleRpcScheduler$1.run(SimpleRpcScheduler.java:110)
        at java.lang.Thread.run(Thread.java:744)
{code}

Then the fella w/ the lock is doing this:

{code}
"regionserver60020.logRoller" daemon prio=10 tid=0x0000000001159800 nid=0x3ca7 in Object.wait()
[0x00007fdb0f964000]
   java.lang.Thread.State: WAITING (on object monitor)
        at java.lang.Object.wait(Native Method)
        at java.lang.Object.wait(Object.java:503)
        at org.apache.hadoop.hbase.regionserver.wal.FSHLog.syncer(FSHLog.java:1307)
        - locked <0x0000000456bf37a8> (a java.util.concurrent.atomic.AtomicLong)
        at org.apache.hadoop.hbase.regionserver.wal.FSHLog.syncer(FSHLog.java:1299)
        at org.apache.hadoop.hbase.regionserver.wal.FSHLog.sync(FSHLog.java:1412)
        at org.apache.hadoop.hbase.regionserver.wal.FSHLog.cleanupCurrentWriter(FSHLog.java:760)
        at org.apache.hadoop.hbase.regionserver.wal.FSHLog.rollWriter(FSHLog.java:566)
        - locked <0x0000000456c00390> (a java.lang.Object)
        - locked <0x0000000456c00330> (a java.lang.Object)
        at org.apache.hadoop.hbase.regionserver.LogRoller.run(LogRoller.java:96)
        at java.lang.Thread.run(Thread.java:744)
{code}

Server is bound up.

> 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
>         Attachments: 8755-syncer.patch, 8755trunkV2.txt, HBASE-8755-0.94-V0.patch, HBASE-8755-0.94-V1.patch,
HBASE-8755-0.96-v0.patch, HBASE-8755-trunk-V0.patch, HBASE-8755-trunk-V1.patch, HBASE-8755-trunk-v4.patch,
HBASE-8755-trunk-v6.patch, HBASE-8755-trunk-v7.patch, HBASE-8755-v5.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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