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From David Alves <dal...@student.dei.uc.pt>
Subject Re: Full table scan fails during map
Date Thu, 20 Nov 2008 18:41:00 GMT
Hi stack

	Regarding the missing block part, my bad, i ddn't install this  
cluster and didn't verify the ulimit first, then a new problem arose  
because of the number of xceivers. Regarding this property, I can't  
find the default value in hadoop-default.xml is this normal? I ask  
only because sometime ago you answered to someone to increase the  
dfs.datanode.max.xcievers proeprty but actually the exceptions refer  
to an *Xceiver (notice the change in the i,e order). Anyway the  
problem seemed to go away so probably that fixed it.
	Regarding the hang part the regionserver actually comes down (no more  
jvm process), next time it happens I'll investigate further.
	Btw Hbase has 2048 MB allocated, we have lots of columns but only  
three CFs, and we use a home grown crawler because we are crawling SVN  
and CVS and other exotic file systems.

Regards, aand thanks for you prompt help, again :)
David Alves

On Nov 20, 2008, at 6:26 PM, stack wrote:

> David Alves wrote:
>> Hi guys
>>    We've got HBase(0.18.0, r695089) and Hadoop(0.18.0, r686010)  
>> running for a while, and apart from the ocasional regionserver  
>> stopping without notice (and whithout explanations from what we can  
>> see in the logs), problem that we solve easily just by restarting  
>> it, we now have come to face a more serious problem of what I think  
>> is data loss.
> What you think it is David?  A hang?  We've seen occasional hangups  
> on HDFS.   You could try threaddumping and see if you can figure  
> where things are blocked (Can do it in UI on problematic  
> regionserver or by sending QUIT to the JVM PID).
>>    We use Hbase as a links and documents database (similar to  
>> nutch) in a 3 node cluster (4GB Mem on each node), the links  
>> database has a 4 regions and the document database now has 200  
>> regions for a total of 216 (with meta and root).
> How much RAM allocated to HBase?  Each database has a single family  
> or more?
>>    After the crawl task, which went ok, (we now have 60GB/300GB  
>> full in hdfs) we proceed to do a full table scan to create the  
>> indexes and thats where things started to fail.
>>    We are seing a problem in the logs (at the end of this email).  
>> This repeats untils theres a retriesexausted exception and the task  
>> fails in the map phase. Hadoop fsk tool tells us that hdfs is ok.  
>> I'm still to explore the rest of the logs searching for some kind  
>> of error I will post a new mail if I find anything.
>>    Any help would be greatly appreciated.
> Is this file in your HDFS: hdfs://cyclops-prod-1:9000/hbase/document/ 
> 153945136/docDatum/mapfiles/5163556575658593611/data?  If so, can  
> you fetch it using ./bin/hadoop fs -get FILENAME?
> What crawler are you using (out of interest).
> St.Ack

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