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From "Billy Pearson (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-2587) Splits getting blocked by compactions causeing region to be offline for the length of the compaction 10-15 mins
Date Mon, 14 Jan 2008 00:50:34 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-2587?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12558476#action_12558476

Billy Pearson commented on HADOOP-2587:

This solves the problem if the region going offline as reported by the region server GUI.
I upload a log of the test I done and the region is doing a compaction for 2mins, 32sec and
then starts the slits and the region server shows the region online for the compaction but
I can not select from the table during the compaction pending the split. Everything just goes
on hold until the compaction is done. 

This causes the same problem as I posted when filling the bug a region should not be off line
for more then a few secs while the region splits. On my test it was off line for 2mins, 32
secs could not read or write to the table. so not sure but  thank the split is still blocking
if this was a full size region on my server they take 10-15 mins to compact when set to 64MB.
So the region would not be usable for the length of the compaction.

I also started to get errors like this
2008-01-13 18:31:14,314 WARN org.apache.hadoop.ipc.Server: IPC Server handler 5 on 60020,
call batchUpdate(webdata,,1200269242626, 9223372036854775807, org.apache.hadoop.hbase.io.BatchUpdate@19762f)
from discarded for being too old (156132)
the log is attached as log.log

> Splits getting blocked by compactions causeing region to be offline for the length of
the compaction 10-15 mins
> ---------------------------------------------------------------------------------------------------------------
>                 Key: HADOOP-2587
>                 URL: https://issues.apache.org/jira/browse/HADOOP-2587
>             Project: Hadoop
>          Issue Type: Bug
>          Components: contrib/hbase
>         Environment: hadoop subversion 611087
>            Reporter: Billy Pearson
>            Assignee: Jim Kellerman
>             Fix For: 0.16.0
>         Attachments: hbase-root-regionserver-PE1750-3.log, log.log, patch.txt
> The below is cut out of one of my region servers logs full log attached
> What is happening is there is one region on a this region server and its is under heave
insert load so compaction are back to back one one finishes a new one starts the problem starts
when its time to split the region. 
> A compaction starts just millsecs before the split starts blocking the split but the
split closes the region before the compaction is finished. Causing the region to be offline
until the compaction is done. Once the compaction is done the split finishes and all is returned
to normal but this is a big problem for production if the region is offline for 10-15 mins.
> The solution would be not to let the split thread to issue the below line while a compaction
on that region is happening.
> 2008-01-11 16:22:01,247 DEBUG org.apache.hadoop.hbase.HRegionServer: webdata,,1200085987488
closing (Adding to retiringRegions)
> The only time I have seen this bug is when there is only one region on a region server
because if more then one then the compaction happens to the other region(s) after the first
one is done compaction and the split can do what it needs on the first region with out getting
> {code}
> 2008-01-11 16:22:01,020 INFO org.apache.hadoop.hbase.HRegion: compaction completed on
region webdata,,1200085987488. Took 16mins, 10sec
> 2008-01-11 16:22:01,020 DEBUG org.apache.hadoop.hbase.HStore: compaction for HStore webdata,,1200085987488/size
> 2008-01-11 16:22:01,020 DEBUG org.apache.hadoop.hbase.HRegion: 1773667150/size needs
> 2008-01-11 16:22:01,021 INFO org.apache.hadoop.hbase.HRegion: starting compaction on
region webdata,,1200085987488
> 2008-01-11 16:22:01,021 DEBUG org.apache.hadoop.hbase.HStore: started compaction of 14
files using /gfs_storage/hadoop-root/hbase/hregion_1773667150/compaction.dir/hregion_1773667150/size
for webdata,,1200085987488/size
> 2008-01-11 16:22:01,123 DEBUG org.apache.hadoop.hbase.HRegion: Started memcache flush
for region webdata,,1200085987488. Size 31.2m
> 2008-01-11 16:22:01,232 INFO org.apache.hadoop.hbase.HRegion: Splitting webdata,,1200085987488
because largest aggregate size is 100.7m and desired size is 64.0m
> 2008-01-11 16:22:01,247 DEBUG org.apache.hadoop.hbase.HRegionServer: webdata,,1200085987488
closing (Adding to retiringRegions)
> ...
> lots of NotServingRegionException's
> ...
> 2008-01-11 16:32:59,876 INFO org.apache.hadoop.hbase.HRegion: compaction completed on
region webdata,,1200085987488. Took 10mins, 58sec
> ...
> 2008-01-11 16:33:02,193 DEBUG org.apache.hadoop.hbase.HRegion: Cleaned up /gfs_storage/hadoop-root/hbase/hregion_1773667150/splits
> 2008-01-11 16:33:02,194 INFO org.apache.hadoop.hbase.HRegion: Region split of webdata,,1200085987488
complete; new regions: webdata,,1200090121237, webdata,com.tom.ent/2008-01-04/0PGM/09034104.html:http,1200090121239.
Split took 11mins, 0sec
> 2008-01-11 16:33:02,227 DEBUG org.apache.hadoop.hbase.HConnectionManager$TableServers:
No servers for .META.. Doing a find...
> 2008-01-11 16:33:02,283 DEBUG org.apache.hadoop.hbase.HConnectionManager$TableServers:
Found 1 region(s) for .META. at address:, regioninfo: regionname: -ROOT-,,0,
startKey: <>, encodedName(70236052) tableDesc: {name: -ROOT-, families: {info:={name:
info, max versions: 1, compression: NONE, in memory: false, max length: 2147483647, bloom
filter: none}}}
> 2008-01-11 16:33:02,284 INFO org.apache.hadoop.hbase.HRegionServer: Updating .META. with
region split info
> 2008-01-11 16:33:02,290 DEBUG org.apache.hadoop.hbase.HRegionServer: Reporting region
split to master
> 2008-01-11 16:33:02,291 INFO org.apache.hadoop.hbase.HRegionServer: region split, META
update, and report to master all successful. Old region=webdata,,1200085987488, new regions:
webdata,,1200090121237, webdata,com.tom.ent/2008-01-04/0PGM/09034104.html:http,1200090121239
> {code}

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