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From "Eugene Koifman (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-11388) there should only be 1 Initiator for compactions per Hive installation
Date Wed, 11 Nov 2015 04:46:11 GMT

    [ https://issues.apache.org/jira/browse/HIVE-11388?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14999937#comment-14999937
] 

Eugene Koifman commented on HIVE-11388:
---------------------------------------

A simpler idea:
The Initiator places a row in COMPACTION_QUEUE to 'schedule' a compaction.
Before that it generates an ID from NEXT_COMPACTION_QUEUE_ID.
With HIVE-11948 we have support for SELECT FOR UPDATE on every DB except Derby, though even
w/o it we have Serializable isolation.  Either way we should be able to check that (db,table,partition,state=Initiated/Working)
combination is unique.  

This allows Initiator to run on any/every metastore while ensuring there is no double-compaction
happening.  

Need to come up with a solution for Cleaner.  Could add another state, such as 'bc'= being
cleaned, so that 1 cleaner marks a row as bc, and then others ignore it.  (This just needs
to be cleaned up on failure)

This avoids the ZK.

> there should only be 1 Initiator for compactions per Hive installation
> ----------------------------------------------------------------------
>
>                 Key: HIVE-11388
>                 URL: https://issues.apache.org/jira/browse/HIVE-11388
>             Project: Hive
>          Issue Type: Bug
>          Components: Transactions
>    Affects Versions: 1.0.0
>            Reporter: Eugene Koifman
>            Assignee: Eugene Koifman
>
> org.apache.hadoop.hive.ql.txn.compactor.Initiator is a thread that runs inside the metastore
service to manage compactions of ACID tables.  There should be exactly 1 instance of this
thread (even with multiple Thrift services).
> This is documented in https://cwiki.apache.org/confluence/display/Hive/Hive+Transactions#HiveTransactions-Configuration
but not enforced.
> Should add enforcement, since more than 1 Initiator could cause concurrent attempts to
compact the same table/partition - which will not work.



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