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From "Dave Latham (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-14247) Separate the old WALs into different regionserver directories
Date Wed, 02 Aug 2017 23:04:00 GMT

    [ https://issues.apache.org/jira/browse/HBASE-14247?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16111893#comment-16111893
] 

Dave Latham commented on HBASE-14247:
-------------------------------------

I don't think that more threads is a great solution.  It still means that, in a cluster using
replication, for every region server's log directory, a thread will need to read all the replication
queues (size also proportional to the number of region servers) in ZK, instead of just happening
once per chore.  This gives O(N^2) performance for N region servers, and is not just theoretical
but has actually caused problems in the past on large clusters (>1000 nodes).  With multiple
threads, it likely still won't be fast enough and may end up hammering ZK if the number of
threads is ramped up too high to compensate.

> Separate the old WALs into different regionserver directories
> -------------------------------------------------------------
>
>                 Key: HBASE-14247
>                 URL: https://issues.apache.org/jira/browse/HBASE-14247
>             Project: HBase
>          Issue Type: Improvement
>          Components: wal
>            Reporter: Liu Shaohui
>            Assignee: Guanghao Zhang
>            Priority: Critical
>             Fix For: 2.0.0
>
>         Attachments: HBASE-14247-v001.diff, HBASE-14247-v002.diff, HBASE-14247-v003.diff
>
>
> Currently all old WALs of regionservers are achieved into the single directory of oldWALs.
In big clusters, because of long TTL of WAL or disabled replications, the number of files
under oldWALs may reach the max-directory-items limit of HDFS, which will make the hbase cluster
crashed.
> {quote}
> Caused by: org.apache.hadoop.ipc.RemoteException(org.apache.hadoop.hdfs.protocol.FSLimitException$MaxDirectoryItemsExceededException):
The directory item limit of /hbase/lgprc-xiaomi/.oldlogs is exceeded: limit=1048576 items=1048576
> {quote}
> A simple solution is to separate the old WALs into different  directories according to
the server name of the WAL.
> Suggestions are welcomed~ Thanks



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