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https://issues.apache.org/jira/browse/HBASE-13539?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Andrew Kyle Purtell resolved HBASE-13539.
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Resolution: Not A Problem
> Clean up empty WAL directories
> ------------------------------
>
> Key: HBASE-13539
> URL: https://issues.apache.org/jira/browse/HBASE-13539
> Project: HBase
> Issue Type: Bug
> Components: wal
> Affects Versions: 1.0.0
> Reporter: Sean Busbey
> Priority: Minor
>
> On HMaster startup, we look for wal directories that can indicate the need
> for recovery. IF there are files in the wal directories, we go through the
> whole recovery process and eventually delete the directory. However, if the
> directory is empty we skip over it as a non-error condition.
> I think the intention for hte empty ones is we could just reuse them.
> Unfortunately, since our wal directories include a server-start timestamp we
> don't reuse them and instead keep around a bunch of old directories.
> ex, this server is only running 1 RS. It has been through some issues.
> {code}
> [busbey@edge ~]$ sudo -u hdfs hdfs dfs -ls -d
> /hbase/WALs/rack03server22.hbase.example.com*
> drwxrwxrwx - hbase hbase 0 2015-04-04 20:16
> /hbase/WALs/rack03server22.hbase.example.com,22101,1428202830692
> drwxrwxrwx - hbase hbase 0 2015-04-05 02:54
> /hbase/WALs/rack03server22.hbase.example.com,22101,1428204146406
> drwxr-xr-x - hbase hbase 0 2015-04-06 14:20
> /hbase/WALs/rack03server22.hbase.example.com,22101,1428227900589
> drwxr-xr-x - hbase hbase 0 2015-04-07 13:17
> /hbase/WALs/rack03server22.hbase.example.com,22101,1428355397531
> drwxr-xr-x - hbase hbase 0 2015-04-08 10:12
> /hbase/WALs/rack03server22.hbase.example.com,22101,1428438216546
> drwxr-xr-x - hbase hbase 0 2015-04-08 12:30
> /hbase/WALs/rack03server22.hbase.example.com,22101,1428513527999
> drwxr-xr-x - hbase hbase 0 2015-04-10 07:40
> /hbase/WALs/rack03server22.hbase.example.com,22101,1428521782656
> drwxr-xr-x - hbase hbase 0 2015-04-10 08:23
> /hbase/WALs/rack03server22.hbase.example.com,22101,1428677010976
> drwxr-xr-x - hbase hbase 0 2015-04-10 08:53
> /hbase/WALs/rack03server22.hbase.example.com,22101,1428679573094
> drwxr-xr-x - hbase hbase 0 2015-04-13 10:26
> /hbase/WALs/rack03server22.hbase.example.com,22101,1428681379039
> drwxr-xr-x - hbase hbase 0 2015-04-19 15:28
> /hbase/WALs/rack03server22.hbase.example.com,22101,1428946164686
> drwxr-xr-x - hbase hbase 0 2015-04-19 15:36
> /hbase/WALs/rack03server22.hbase.example.com,22101,1429482692579
> drwxr-xr-x - hbase hbase 0 2015-04-21 15:43
> /hbase/WALs/rack03server22.hbase.example.com,22101,1429652628679-splitting
> drwxr-xr-x - hbase hbase 0 2015-04-22 07:14
> /hbase/WALs/rack03server22.hbase.example.com,22101,1429665239905
> drwxr-xr-x - hbase hbase 0 2015-04-22 08:04
> /hbase/WALs/rack03server22.hbase.example.com,22101,1429714674479
> drwxr-xr-x - hbase hbase 0 2015-04-22 08:37
> /hbase/WALs/rack03server22.hbase.example.com,22101,1429715217130
> drwxr-xr-x - hbase hbase 0 2015-04-22 10:28
> /hbase/WALs/rack03server22.hbase.example.com,22101,1429717221567
> drwxr-xr-x - hbase hbase 0 2015-04-22 11:14
> /hbase/WALs/rack03server22.hbase.example.com,22101,1429723761988
> drwxr-xr-x - hbase hbase 0 2015-04-23 08:17
> /hbase/WALs/rack03server22.hbase.example.com,22101,1429726649267
> [busbey@edge ~]$
> {code}
> Most of those are empty from previous clean restarts. It does still have
> * 1 current WAL that it's using for current operations
> * 1 previous wal that is in recovery
> * 1 previous wal from a failure that hasn't been recognized yet (it restarted
> again while all masters are down)
> And those are easily seen in the non-empty directories
> {code}
> [busbey@edge ~]$ sudo -u hdfs hdfs dfs -ls
> /hbase/WALs/rack03server22.hbase.example.com*
> Found 1 items
> -rw-r--r-- 3 hbase hbase 83 2015-04-21 15:43
> /hbase/WALs/rack03server22.hbase.example.com,22101,1429652628679-splitting/rack03server22.hbase.example.com%2C22101%2C1429652628679.default.1429656231067
> Found 1 items
> -rw-r--r-- 3 hbase hbase 83 2015-04-22 07:14
> /hbase/WALs/rack03server22.hbase.example.com,22101,1429665239905/rack03server22.hbase.example.com%2C22101%2C1429665239905.default.1429712050345
> Found 1 items
> -rw-r--r-- 3 hbase hbase 83 2015-04-23 08:17
> /hbase/WALs/rack03server22.hbase.example.com,22101,1429726649267/rack03server22.hbase.example.com%2C22101%2C1429726649267.default.1429802256366
> [busbey@edge ~]$
> {code}
> So maybe we need an additional cleanup action on becomine active master that
> removes empty previous wal directories.
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