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From "stack (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-1730) online schema and tableAdd updates
Date Thu, 29 Oct 2009 23:58:59 GMT

    [ https://issues.apache.org/jira/browse/HBASE-1730?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12771705#action_12771705
] 

stack commented on HBASE-1730:
------------------------------

Going to serialize HTD and HCD to zk as JSON; this seems easiest way to go for schema.  Will
remove notion of state change from HTD and HCD though.  For instance if a region is offline,
you won't know by reading the .META.; master will know because will have read state from zk.

@apurtell I should use jackson for pojo 2 json because thats what you and avro are using.
 One concern is versions.  Jackson is up to 1.2.  avro is jackson-core-asl-1.0.1.jar.  Stargate
is 0.94.  Let me start with the version in stargate.  OK I pull it up to trunk/lib?  You can
get it when its there?  Can I update to 1.0.1?

> online schema and tableAdd updates
> ----------------------------------
>
>                 Key: HBASE-1730
>                 URL: https://issues.apache.org/jira/browse/HBASE-1730
>             Project: Hadoop HBase
>          Issue Type: Improvement
>            Reporter: Andrew Purtell
>            Assignee: stack
>             Fix For: 0.21.0
>
>
> We should not need to take a table offline to update HCD or HTD. 
> One option for that is putting HTDs and HCDs up into ZK, with mirror on disk catalog
tables to be used only for cold init scenarios, as discussed on IRC. In this scheme, regionservers
hosting regions of a table would watch permanent nodes in ZK associated with that table for
schema updates and take appropriate actions out of the watcher. In effect, schema updates
become another item in the ToDo list.
> {{/hbase/tables/<table-name>/schema}}
> Must be associated with a write locking scheme also handled with ZK primitives to avoid
situations where one concurrent update clobbers another. 

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