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

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

    [ https://issues.apache.org/jira/browse/HBASE-1730?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12738152#action_12738152 ] 

Jim Kellerman commented on HBASE-1730:
--------------------------------------

+1 for putting descriptions both on disk for cold start and in ZK for on-line.

As for format, how about Avro (which is json based)?

> 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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