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From "ramkrishna.s.vasudevan (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-10499) In write heavy scenario one of the regions does not get flushed causing RegionTooBusyException
Date Mon, 17 Feb 2014 12:13:20 GMT

    [ https://issues.apache.org/jira/browse/HBASE-10499?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13903168#comment-13903168
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ramkrishna.s.vasudevan commented on HBASE-10499:
------------------------------------------------

bq.If we suppose these two regions have the same problem regarding non-flush-able internally
by regionserver, and 6b788c498503ddd3e1433a4cd3fb4e39 is successfully flushed by a sub-phase
of close operation because flush as part of close doesn't bother flushQueue
This is one thing I have not noticed that while flush happens via close then flushQueue is
not used.  By design that makes sense.  
One thing I wanted to raise a JIRA is that should flushregionentry use EnvirnonmentEdge.currentMillis
instead of System.currentMilllis.  I don't know how far it benefits but I think that can be
done.
So there is some reason why flushQueue is not picking up that region? 

> In write heavy scenario one of the regions does not get flushed causing RegionTooBusyException
> ----------------------------------------------------------------------------------------------
>
>                 Key: HBASE-10499
>                 URL: https://issues.apache.org/jira/browse/HBASE-10499
>             Project: HBase
>          Issue Type: Bug
>    Affects Versions: 0.98.0
>            Reporter: ramkrishna.s.vasudevan
>            Assignee: ramkrishna.s.vasudevan
>            Priority: Critical
>             Fix For: 0.98.1, 0.99.0
>
>         Attachments: HBASE-10499.patch, hbase-root-master-ip-10-157-0-229.zip, hbase-root-regionserver-ip-10-93-128-92.zip,
master_4e39.log, master_576f.log, rs_4e39.log, rs_576f.log, t1.dump, t2.dump, workloada_0.98.dat
>
>
> I got this while testing 0.98RC.  But am not sure if it is specific to this version.
 Doesn't seem so to me.  
> Also it is something similar to HBASE-5312 and HBASE-5568.
> Using 10 threads i do writes to 4 RS using YCSB. The table created has 200 regions. 
In one of the run with 0.98 server and 0.98 client I faced this problem like the hlogs became
more and the system requested flushes for those many regions.
> One by one everything was flushed except one and that one thing remained unflushed. 
The ripple effect of this on the client side
> {code}
> com.yahoo.ycsb.DBException: org.apache.hadoop.hbase.client.RetriesExhaustedWithDetailsException:
Failed 54 actions: RegionTooBusyException: 54 times,
>         at com.yahoo.ycsb.db.HBaseClient.cleanup(HBaseClient.java:245)
>         at com.yahoo.ycsb.DBWrapper.cleanup(DBWrapper.java:73)
>         at com.yahoo.ycsb.ClientThread.run(Client.java:307)
> Caused by: org.apache.hadoop.hbase.client.RetriesExhaustedWithDetailsException: Failed
54 actions: RegionTooBusyException: 54 times,
>         at org.apache.hadoop.hbase.client.AsyncProcess$BatchErrors.makeException(AsyncProcess.java:187)
>         at org.apache.hadoop.hbase.client.AsyncProcess$BatchErrors.access$500(AsyncProcess.java:171)
>         at org.apache.hadoop.hbase.client.AsyncProcess.getErrors(AsyncProcess.java:897)
>         at org.apache.hadoop.hbase.client.HTable.backgroundFlushCommits(HTable.java:961)
>         at org.apache.hadoop.hbase.client.HTable.flushCommits(HTable.java:1225)
>         at com.yahoo.ycsb.db.HBaseClient.cleanup(HBaseClient.java:232)
>         ... 2 more
> {code}
> On one of the RS
> {code}
> 2014-02-11 08:45:58,714 INFO  [regionserver60020.logRoller] wal.FSHLog: Too many hlogs:
logs=38, maxlogs=32; forcing flush of 23 regions(s): 97d8ae2f78910cc5ded5fbb1ddad8492, d396b8a1da05c871edcb68a15608fdf2,
01a68742a1be3a9705d574ad68fec1d7, 1250381046301e7465b6cf398759378e, 127c133f47d0419bd5ab66675aff76d4,
9f01c5d25ddc6675f750968873721253, 29c055b5690839c2fa357cd8e871741e, ca4e33e3eb0d5f8314ff9a870fc43463,
acfc6ae756e193b58d956cb71ccf0aa3, 187ea304069bc2a3c825bc10a59c7e84, 0ea411edc32d5c924d04bf126fa52d1e,
e2f9331fc7208b1b230a24045f3c869e, d9309ca864055eddf766a330352efc7a, 1a71bdf457288d449050141b5ff00c69,
0ba9089db28e977f86a27f90bbab9717, fdbb3242d3b673bbe4790a47bc30576f, bbadaa1f0e62d8a8650080b824187850,
b1a5de30d8603bd5d9022e09c574501b, cc6a9fabe44347ed65e7c325faa72030, 313b17dbff2497f5041b57fe13fa651e,
6b788c498503ddd3e1433a4cd3fb4e39, 3d71274fe4f815882e9626e1cfa050d1, acc43e4b42c1a041078774f4f20a3ff5
> ......................................................
> 2014-02-11 08:47:49,580 INFO  [regionserver60020.logRoller] wal.FSHLog: Too many hlogs:
logs=53, maxlogs=32; forcing flush of 2 regions(s): fdbb3242d3b673bbe4790a47bc30576f, 6b788c498503ddd3e1433a4cd3fb4e39
> {code}
> {code}
> 2014-02-11 09:42:44,237 INFO  [regionserver60020.periodicFlusher] regionserver.HRegionServer:
regionserver60020.periodicFlusher requesting flush for region usertable,user3654,1392107806977.fdbb3242d3b673bbe4790a47bc30576f.
after a delay of 16689
> 2014-02-11 09:42:44,237 INFO  [regionserver60020.periodicFlusher] regionserver.HRegionServer:
regionserver60020.periodicFlusher requesting flush for region usertable,user6264,1392107806983.6b788c498503ddd3e1433a4cd3fb4e39.
after a delay of 15868
> 2014-02-11 09:42:54,238 INFO  [regionserver60020.periodicFlusher] regionserver.HRegionServer:
regionserver60020.periodicFlusher requesting flush for region usertable,user3654,1392107806977.fdbb3242d3b673bbe4790a47bc30576f.
after a delay of 20847
> 2014-02-11 09:42:54,238 INFO  [regionserver60020.periodicFlusher] regionserver.HRegionServer:
regionserver60020.periodicFlusher requesting flush for region usertable,user6264,1392107806983.6b788c498503ddd3e1433a4cd3fb4e39.
after a delay of 20099
> 2014-02-11 09:43:04,238 INFO  [regionserver60020.periodicFlusher] regionserver.HRegionServer:
regionserver60020.periodicFlusher requesting flush for region usertable,user3654,1392107806977.fdbb3242d3b673bbe4790a47bc30576f.
after a delay of 8677
> {code}
> {code}
> 2014-02-11 10:31:21,020 INFO  [regionserver60020.logRoller] wal.FSHLog: Too many hlogs:
logs=54, maxlogs=32; forcing flush of 1 regions(s): fdbb3242d3b673bbe4790a47bc30576f
> {code}
> I restarted another RS and there were region movements with other regions but this region
stays with the RS that has this issue.  One important observation is that in HRegion.internalflushCache()
we need to add a debug log here
> {code}
> // If nothing to flush, return and avoid logging start/stop flush.
>     if (this.memstoreSize.get() <= 0) {
>       return false;
>     }
> {code}
> Because we can see that the region is requsted for a flush but it does not happen and
no logs related to flush are printed in the logs. so due to some reason this memstore.size()
has become 0( I assume this).  The earlier bugs were also due to similar reason.



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