[jira] [Commented] (HIVE-14065) Provide an API for making Hive read-only for a short period

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

    [ https://issues.apache.org/jira/browse/HIVE-14065?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15340696#comment-15340696 ] 

Alan Gates commented on HIVE-14065:
-----------------------------------

I'm unclear what you mean by "taking all the ZooKeeper locks".  Can you elaborate?

> Provide an API for making Hive read-only for a short period
> -----------------------------------------------------------
>
>                 Key: HIVE-14065
>                 URL: https://issues.apache.org/jira/browse/HIVE-14065
>             Project: Hive
>          Issue Type: Improvement
>            Reporter: Colin Patrick McCabe
>            Assignee: Colin Patrick McCabe
>
> HIVE-7973 added a notification log which allows clients to do incremental replication of the Hive metastore.  However, it is a challenge to get the initial state of the Hive database.  Using existing APIs may give us an inconsistent state.  For example, if a Hive table is renamed while we're loading all tables, we may miss that information.
> The easiest way to fix this would be to provide an API for making Hive read-only for a short period.  This locking API would come with a timeout so that if the locker failed, the system would not stay down.  It would return an ID which uniquely identified the lock instance.  The read-only lock itself could be implemented by taking all the ZooKeeper locks.  The RPC for removing the lock would return back a status indicating whether the lock had timed out before being removed or not.  If it had timed out, we could retry our snapshot loading process with a longer timeout period.



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