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From "rajeshbabu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-8348) Polish the migration to 0.96
Date Tue, 30 Jul 2013 13:11:52 GMT

    [ https://issues.apache.org/jira/browse/HBASE-8348?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13723834#comment-13723834
] 

rajeshbabu commented on HBASE-8348:
-----------------------------------

[~himanshu@cloudera.com]
bq. ROOT? Or you mean FIRST_META_REGIONINFO?
Its ROOT only.Before migrating to 0.95.x, root table files will be left out in file system,
from that scanning .META. server address to create META server znode. This will be helpful
during master initialization to identify .META. server is dead or not. Ideally it should help
in splitting META logs but in 0.95.x meta hlog files are suffixed with "meta", so cannot find
them in older versions hlogs. If we dont flush .META. and -ROOT- tables before stopping the
existing cluter, there may be chance of loosing recently created tables.

bq. I wonder the utility of migrating the existing znodes / or creating meta server znodes
while doing the migration to 0.95. Why not let HBase create them out of the box?
zookeeper.znode.tableEnableDisable znode helps to find the exact state of the table, It will
be better to migrate table states to PB instead of deleting them. Otherwise even if tables
are disabled, they will be enabled during master initialization.

bq. What if we fail in the middle of this znode upgrade? 
User can retry, otherwise master initialization may fail. Ex: HBASE-7766

                
> Polish the migration to 0.96
> ----------------------------
>
>                 Key: HBASE-8348
>                 URL: https://issues.apache.org/jira/browse/HBASE-8348
>             Project: HBase
>          Issue Type: Bug
>    Affects Versions: 0.95.0
>            Reporter: Jean-Daniel Cryans
>            Assignee: rajeshbabu
>            Priority: Critical
>             Fix For: 0.95.2
>
>         Attachments: HBASE-8348_trunk.patch, HBASE-8348_trunk_v2.patch
>
>
> Currently, migration works but there's still a couple of rough edges:
>  - HBASE-8045 finished the .META. migration but didn't remove ROOT, so it's still on
the filesystem.
>  - Data in ZK needs to be removed manually. Either we fix up the data in ZK or we delete
it ourselves.
>  - TestMetaMigrationRemovingHTD has a testMetaUpdatedFlagInROOT method, but ROOT is gone
now.
> Elliott was also mentioning that we could have "hbase migrate" do the HFileV1 checks,
clear ZK, remove ROOT, etc.

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