[jira] [Resolved] (HBASE-22628) Document the custom WAL directory (hbase.wal.dir) usage

["Reid Chan (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HBASE-22628?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Reid Chan resolved HBASE-22628.
-------------------------------
    Resolution: Fixed

> Document the custom WAL directory (hbase.wal.dir) usage
> -------------------------------------------------------
>
>                 Key: HBASE-22628
>                 URL: https://issues.apache.org/jira/browse/HBASE-22628
>             Project: HBase
>          Issue Type: Improvement
>          Components: documentation, wal
>            Reporter: Pankaj Kumar
>            Assignee: Pankaj Kumar
>            Priority: Major
>             Fix For: 3.0.0
>
>         Attachments: 002-view.png, HBASE-22628.002.patch, HBASE-22628.patch, Screenshot-HBASE-22628.png
>
>
> Custom WAL directory usage must be documented, otherwise it may lead to inconsistent data during migrating to new WAL dir path.
>  
> You can consider below scenario while migrating to custom WAL directory.
>  # Setup HBase cluster with the default setting (all WAL files are under the root directory ie. /hbase/WALs).
>  # Create table 't1' and insert few records
>  # Flush meta table (so that table region entries persist in FS)
>  # Forcibly kill HBase processes (HM & RS).
>  # Configure the hbase.wal.dir to outside the root dir (say /hbaseWAL)
>  # Start the HBase servers
>  # Scan 't1'
> Ideally HMaster should submit split task of old RS(s) WAL files (created under /hbase/WALs) and old data should be replayed. But currently, during HM startup we populate the previous dead servers from the current WAL dir ( hbase.wal.dir -> /hbaseWAL).
>  
> Since WAL dir path is new, so you need to copy RegionServer WAL directories manualy from old WAL dir to new path. 



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