[jira] [Commented] (HBASE-21073) "Maintenance mode" master

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

    [ https://issues.apache.org/jira/browse/HBASE-21073?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16893167#comment-16893167 ] 

stack commented on HBASE-21073:
-------------------------------

Some notes after trying this feature:

 * UI on Master doesn't show. Does NPE. Would be good if it came up so had access to stuff like Procedures and Locks.
 * Logs show user-space regions as STUCK. Probably just needs doc'ing.
 * These logs are good 'HMaster: Master is in maintenanceMode mode, don't run balancer.' and 'HMaster: Master is in maintenance mode, don't run region normalizer.'  but says this after Master comes up... 'HMaster: Detected repair mode, skipping final initialization steps.'. Should match the other logs of 'maintenance mode'.
 * Here is how I started Master only with the maintenance mode flag: ./bin/hbase-daemon.sh start master -Dhbase.master.maintenance_mode=true Could add to doc.

Not sure if this feature is useful yet. Dump note in here if find it of use.

> "Maintenance mode" master
> -------------------------
>
>                 Key: HBASE-21073
>                 URL: https://issues.apache.org/jira/browse/HBASE-21073
>             Project: HBase
>          Issue Type: Sub-task
>          Components: amv2, hbck2, master
>            Reporter: stack
>            Assignee: Mike Drob
>            Priority: Major
>             Fix For: 3.0.0, 2.2.0, 2.1.1, 2.0.3
>
>         Attachments: HBASE-21073.branch-2.001.patch, HBASE-21073.branch-2.1.001.patch, HBASE-21073.branch-2.1.002.patch, HBASE-21073.master.001.patch, HBASE-21073.master.002.patch, HBASE-21073.master.003.patch, HBASE-21073.master.004.patch, HBASE-21073.master.005.patch, HBASE-21073.master.006.patch, HBASE-21073.master.007.patch, HBASE-21073.master.008.patch, HBASE-21073.master.009.patch, HBASE-21073.master.010.patch, HBASE-21073.master.011.patch
>
>
> Make it so we can bring up a Master in "maintenance mode". This is parse of master wal procs but not taking on regionservers. It would be in a state where "repair" Procedures could run; e.g. a Procedure that could recover meta by looking for meta WALs, splitting them, dropping recovered.edits, and even making it so meta is readable. See parent issue for why needed (disaster recovery).



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