[jira] Commented: (HBASE-1730) online schema updates

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

    [ https://issues.apache.org/jira/browse/HBASE-1730?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12737688#action_12737688 ] 

ryan rawson commented on HBASE-1730:
------------------------------------

lets decide on a serialization format to use within ZK, that is NOT hadoop writables.  I would vote for JSON since the data is small, and it would be nice for it to be human readable without programmatic intervention.

> online schema updates
> ---------------------
>
>                 Key: HBASE-1730
>                 URL: https://issues.apache.org/jira/browse/HBASE-1730
>             Project: Hadoop HBase
>          Issue Type: Improvement
>            Reporter: Andrew Purtell
>             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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