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From Vincent Barat <vincent.ba...@gmail.com>
Subject Re: HBase scanner LeaseException
Date Thu, 22 Nov 2012 08:21:04 GMT
Apparently, my problem seems more related to the one exposed here: 
http://www.nosql.se/tags/hbase-rpc-timeout/

I don't really understand the reason why next() on our scanners is 
called less than once per 60s, and actually I suspect this is NOT 
the case, since we never had any scanner timeout exception when we 
were running 0.90.3, this issue appeared only with 0.92.

Anyway,  increasing hbase.rpc.timeout seems to work.

We will continue our investigation, but my guess is that there is an 
issue in 0.92 related to how hbase handle scanners leases.

Best regards,

Le 21/11/12 09:23, Vincent Barat a écrit :
>
> Le 21/11/12 06:05, Stack a écrit :
>> On Tue, Nov 20, 2012 at 8:21 AM, Vincent Barat 
>> <vincent.barat@gmail.com> wrote:
>>> We have changed some parameters on our 16(!) region servers : 
>>> 1GB more -Xmx,
>>> more rpc handler (from 10 to 30) longer timeout, but nothing 
>>> seems to
>>> improve the response time:
>>>
>> You have taken a look at the perf chapter Vincent:
>> http://hbase.apache.org/book.html#performance
>>
>> You carried forward your old hbase-default.xml or did you remove it
>> (0.92 should have defaults in hbase-X.X.X.jar -- some defaults will
>> have changed).
> We use the new default settings for HBase, just a few changes 
> (more RPC handlers and longer timeout (but this last was a bad idea).
>>> - Scans with HBase 0.92  are x3 SLOWER than with HBase 0.90.3
>> Any scan caching going on?
> yes the cache is set between 64 and 1024 depending on the need
>>> - A lot of simultaneous gets lead to a huge slow down of batch 
>>> put & ramdom
>>> read response time
>>>
>> The gets are returning lots of data? (If you thread dump the 
>> server at
>> this time -- see at top of the regionserver UI -- can you see 
>> what we
>> are hung up on?  Are all handlers occupied?).
> We will check this...
>>> ... despite the fact that our RS CPU load is really low (10%)
>>>
>> As has been suggested earlier, perhaps up the handlers?
>>
>>
>>> Note: we have not (yet) activated MSlabs, nor direct read on HDFS.
>>>
>> MSlab will help you avoid stop-the-world GCs.  Direct read of HDFS
>> should speed up random access.
> OK, I guess we will give it a try, but on a second step.
>
> Thansk for your help
>>
>> St.Ack
>>
>>> Any idea please ? I'm really stuck on that issue.
>>>
>>> Best regards,
>>>
>>> Le 16/11/12 20:55, Vincent Barat a écrit :
>>>> Hi,
>>>>
>>>> Right now (and previously with 0.90.3) we were using the 
>>>> default value
>>>> (10).
>>>> We are trying right now to increase to 30 to see if it is better.
>>>>
>>>> Thanks for your concern
>>>>
>>>> Le 16/11/12 18:13, Ted Yu a écrit :
>>>>> Vincent:
>>>>> What's the value for hbase.regionserver.handler.count ?
>>>>>
>>>>> I assume you keep the same value as that from 0.90.3
>>>>>
>>>>> Thanks
>>>>>
>>>>> On Fri, Nov 16, 2012 at 8:14 AM, Vincent
>>>>> Barat<vincent.barat@gmail.com>wrote:
>>>>>
>>>>>> Le 16/11/12 01:56, Stack a écrit :
>>>>>>
>>>>>>    On Thu, Nov 15, 2012 at 5:21 AM, Guillaume 
>>>>>> Perrot<gperrot@ubikod.com>
>>>>>>> wrote:
>>>>>>>
>>>>>>>> It happens when several tables are being compacted and/or

>>>>>>>> when there
>>>>>>>> is
>>>>>>>> several scanners running.
>>>>>>>>
>>>>>>> It happens for a particular region?  Anything you can tell 
>>>>>>> about the
>>>>>>> server looking in your cluster monitoring?  Is it running 
>>>>>>> hot?  What
>>>>>>> do the hbase regionserver stats in UI say?  Anything 
>>>>>>> interesting about
>>>>>>> compaction queues or requests?
>>>>>>>
>>>>>> Hi, thanks for your answser Stack. I will take the lead on 
>>>>>> that thread
>>>>>> from now on.
>>>>>>
>>>>>> It does not happens on any particular region. Actually, 
>>>>>> things get
>>>>>> better
>>>>>> now since compactions have been performed on all tables and 
>>>>>> have been
>>>>>> stopped.
>>>>>>
>>>>>> Nevertheless, we face a dramatic decrease of performances 
>>>>>> (especially on
>>>>>> random gets) of the overall cluster:
>>>>>>
>>>>>> Despite the fact we double our number of region servers (from 
>>>>>> 8 to 16)
>>>>>> and
>>>>>> despite the fact that these region server CPU load are just 
>>>>>> about 10% to
>>>>>> 30%, performances are really bad : very often an light 
>>>>>> increase of
>>>>>> request
>>>>>> lead to a clients locked on request, very long response time. 
>>>>>> It looks
>>>>>> like
>>>>>> a contention / deadlock somewhere in the HBase client and C 
>>>>>> code.
>>>>>>
>>>>>>
>>>>>>
>>>>>>> If you look at the thread dump all handlers are occupied 
>>>>>>> serving
>>>>>>> requests?  These timedout requests couldn't get into the 
>>>>>>> server?
>>>>>>>
>>>>>> We will investigate on that and report to you.
>>>>>>
>>>>>>
>>>>>>    Before the timeouts, we observe an increasing CPU load on 
>>>>>> a single
>>>>>> region
>>>>>>>> server and if we add region servers and wait for 
>>>>>>>> rebalancing, we
>>>>>>>> always
>>>>>>>> have the same region server causing problems like these:
>>>>>>>>
>>>>>>>> 2012-11-14 20:47:08,443 WARN 
>>>>>>>> org.apache.hadoop.ipc.**HBaseServer: IPC
>>>>>>>> Server Responder, call
>>>>>>>> multi(org.apache.hadoop.hbase.**client.MultiAction@2c3da1aa),

>>>>>>>> rpc
>>>>>>>> version=1, client version=29, methodsFingerPrint=54742778
from
>>>>>>>> <ip>:45334: output error
>>>>>>>> 2012-11-14 20:47:08,443 WARN 
>>>>>>>> org.apache.hadoop.ipc.**HBaseServer: IPC
>>>>>>>> Server handler 3 on 60020 caught: java.nio.channels.**
>>>>>>>> ClosedChannelException
>>>>>>>> at sun.nio.ch.SocketChannelImpl.**ensureWriteOpen(**
>>>>>>>> SocketChannelImpl.java:133)
>>>>>>>> at 
>>>>>>>> sun.nio.ch.SocketChannelImpl.**write(SocketChannelImpl.java:**324)

>>>>>>>>
>>>>>>>> at
>>>>>>>> org.apache.hadoop.hbase.ipc.**HBaseServer.channelWrite(**
>>>>>>>> HBaseServer.java:1653)
>>>>>>>> at
>>>>>>>> org.apache.hadoop.hbase.ipc.**HBaseServer$Responder.
>>>>>>>> processResponse(HBaseServer.**java:924)
>>>>>>>> at
>>>>>>>> org.apache.hadoop.hbase.ipc.**HBaseServer$Responder.
>>>>>>>> doRespond(HBaseServer.java:**1003)
>>>>>>>> at
>>>>>>>> org.apache.hadoop.hbase.ipc.**HBaseServer$Call.**sendResponseIfReady(

>>>>>>>>
>>>>>>>> HBaseServer.java:409)
>>>>>>>> at
>>>>>>>> org.apache.hadoop.hbase.ipc.**HBaseServer$Handler.run(**
>>>>>>>> HBaseServer.java:1346)
>>>>>>>>
>>>>>>>> With the same access patterns, we did not have this issue

>>>>>>>> in HBase
>>>>>>>> 0.90.3.
>>>>>>>>
>>>>>>> The above is other side of the timeout -- the client is gone.
>>>>>>>
>>>>>>> Can you explain the rising CPU?
>>>>>>>
>>>>>> No there is no explanation (no high access a a given region for
>>>>>> exemple).
>>>>>> But this specific problem has gone when we finished compactions.
>>>>>>
>>>>>>
>>>>>>       Is it iowait on this box because of
>>>>>>> compactions?  Bad disk?  Always same regionserver or issue 
>>>>>>> moves
>>>>>>> around?
>>>>>>>
>>>>>>> Sorry for all the questions.  0.92 should be better than 0.90
>>>>>>>
>>>>>> Our experience is currently the exact opposite : for us, 0.92 
>>>>>> seems to
>>>>>> be
>>>>>> times slower than the 0.90.3.
>>>>>>
>>>>>>    generally (0.94 even better still -- can you go there?).
>>>>>> We can go to 0.94 but unfortunately, we CANNOT GO BACK (the 
>>>>>> same way we
>>>>>> cannot go back to 0.90.3, since there is apparently a 
>>>>>> modification of
>>>>>> the
>>>>>> format of the ROOT table).
>>>>>> The upgrade works, but the downgrade not. And we are afraid 
>>>>>> of having
>>>>>> even
>>>>>> more "new" problems with 0.94 and be forced to rollback to 
>>>>>> 0.90.3 (with
>>>>>> some days of data loses).
>>>>>>
>>>>>> Thanks for your reply we will continue to investigate.
>>>>>>
>>>>>>
>>>>>>
>>>>>>       Interesting
>>>>>>> that these issues show up post upgrade.  I can't think of a 
>>>>>>> reason why
>>>>>>> the different versions would bring this on...
>>>>>>>
>>>>>>> St.Ack
>>>>>>>
>>>>>>>
>>>>
>

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