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https://issues.apache.org/jira/browse/HBASE-1994?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12780014#action_12780014
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Andrew Purtell commented on HBASE-1994:
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bq. Or use a UUID style filename for them with a known extension that the RS 
knows how to find and then replays them in order (so filename could be a 
timestamp?).

+1

bq. As for empty .log files we could add an easy check that if empty then 
remove as opposed to rename.

+1


> Master will lose hlog entries while splitting if region has empty 
> oldlogfile.log
> --------------------------------------------------------------------------------
>
>                 Key: HBASE-1994
>                 URL: https://issues.apache.org/jira/browse/HBASE-1994
>             Project: Hadoop HBase
>          Issue Type: Bug
>          Components: master
>    Affects Versions: 0.21.0
>            Reporter: Cosmin Lehene
>            Priority: Blocker
>             Fix For: 0.21.0
>
>   Original Estimate: 48h
>  Remaining Estimate: 48h
>
> I don't know yet how an empty oldlogfile.log can exist, however it happened.
> Master will fail to put the splits in the region oldlogfile.log if an empty 
> oldlogfile.log already exists there.
> This is the master log after I artificially reproduced it by placing an empty 
> oldlogfile.log in /hbase/.META./1028785192/oldlogfile.log and then killed the 
> regionserver that was holding the .META. table
> 2009-11-19 09:08:36,012 INFO org.apache.hadoop.hbase.regionserver.wal.HLog: 
> Splitting 1 hlog(s) in hdfs://b0:9000/hbase/.logs/b4,60020,1258637492773
> 2009-11-19 09:08:36,012 DEBUG org.apache.hadoop.hbase.regionserver.wal.HLog: 
> Splitting hlog 1 of 1: 
> hdfs://b0:9000/hbase/.logs/b4,60020,1258637492773/hlog.dat.1258637493128, 
> length=0
> 2009-11-19 09:08:36,019 DEBUG org.apache.hadoop.hbase.regionserver.wal.HLog: 
> Adding queue for .META.,,1
> 2009-11-19 09:08:36,037 DEBUG org.apache.hadoop.hbase.regionserver.wal.HLog: 
> Pushed=795 entries from 
> hdfs://b0:9000/hbase/.logs/b4,60020,1258637492773/hlog.dat.1258637493128
> 2009-11-19 09:08:36,038 DEBUG org.apache.hadoop.hbase.regionserver.wal.HLog: 
> Thread got 795 to process
> 2009-11-19 09:08:36,043 WARN org.apache.hadoop.hbase.regionserver.wal.HLog: 
> Old hlog file hdfs://b0:9000/hbase/.META./1028785192/oldlogfile.log already 
> exists. Copying existing file to new file
> 2009-11-19 09:08:36,079 WARN org.apache.hadoop.hbase.regionserver.wal.HLog: 
> Got while writing region .META.,,1 log java.io.EOFException
> 2009-11-19 09:08:36,081 INFO org.apache.hadoop.hbase.regionserver.wal.HLog: 
> hlog file splitting completed in 70 millis for 
> hdfs://b0:9000/hbase/.logs/b4,60020,1258637492773

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