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From Dru Jensen <drujen...@gmail.com>
Subject Re: NotServingRegionException - Map/Reduce process fails
Date Thu, 23 Oct 2008 19:07:13 GMT
Stack and J-D, Thanks for your responses.

It looks like the RetriesExhaustedException occurred during:

2008-10-23 11:08:55,180 INFO  
org.apache.hadoop.hbase.regionserver.HRegion: compaction completed on  
region ... 1224785065371 in 4mins, 25sec

It doesn't look like I am having the HBASE-921 issue (yet).

What settings can I change to cause the compaction to not take so long?

I found this setting:

     If more than this number of HStoreFiles in any one HStore
     (one HStoreFile is written per flush of memcache) then a compaction
     is run to rewrite all HStoreFiles files as one.  Larger numbers
     put off compaction but when it runs, it takes longer to complete.
     During a compaction, updates cannot be flushed to disk.  Long
     compactions require memory sufficient to carry the logging of
     all updates across the duration of the compaction.

     If too large, clients timeout during compaction.

Should I lower this or is there a better way?


On Oct 23, 2008, at 11:37 AM, Jean-Daniel Cryans wrote:

> Dru.
> See also if it's a case of
> HBASE-921<https://issues.apache.org/jira/browse/HBASE-921>because it
> would make sense if not using hbase 0.18.1 and under a heavy
> load.
> J-D
> On Thu, Oct 23, 2008 at 2:30 PM, stack <stack@duboce.net> wrote:
>> Find the MR task that failed.  Click through the UI to look at its  
>> logs.
>> It may have interesting info.  Its probably complaining about a  
>> region not
>> being available (NSRE).  Figure which region it is.  Use the region
>> historian or grep in the master logs -- 'grep -v metaScanner  
>> you avoid the metaScanner noise -- to see if you can figure the  
>> regions
>> history around the failure.  Look too at loading around failure  
>> time.  Were
>> you swapping, etc. (Ganglia or some such helps here).
>> You might also test table is still wholesome -- that the MR job  
>> didn't
>> damage the table.  A quick check that all regions are onlined and  
>> accessible
>> is to scan for a column whose column family does exist but whose  
>> qualifier
>> you know is not present: e.g. if you have columnfamily 'page' and  
>> you know
>> there is no column 'page:xyz', scan with that (Enable DEBUG in  
>> log4j so you
>> can see regions being loaded as scan progresses): "scan 'TABLENAME',
>> ['page:xyz']".
>> You might need to up the timeouts/retries.
>> St.Ack
>> Dru Jensen wrote:
>>> Hi hbase-users,
>>> During a fairly large MR process, on the Reduce cycle as its  
>>> writing its
>>> results to a table, I see  
>>> org.apache.hadoop.hbase.NotServingRegionException
>>> in the region server log several times and then I see a split  
>>> reporting it
>>> was successful.
>>> Eventually, the Reduce process fails with
>>> org.apache.hadoop.hbase.client.RetriesExhaustedException after 10  
>>> failed
>>> attempts.
>>> What can I do to fix it?
>>> Thanks,
>>> Dru

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