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From "Keith Turner (JIRA)" <>
Subject [jira] [Commented] (ACCUMULO-420) Allow per compaction iterator settings
Date Tue, 22 May 2012 23:16:41 GMT


Keith Turner commented on ACCUMULO-420:

There is a flaw in my logic above that has nothing to do with zookeeper consistency.  The
following interleaving will lead to the tserver seeing the udpated compaction count but not
the iterators.  This is what I do not want to happen.

 # Tserver : get compaction iterators from zookeeper
 # FATE OP : set compaction iterators in zookeeper
 # FATE OP : increment compaction counter in zookeeper
 # Tserver : get compaction counter in zookeeper

I think the solution is to have the compaction count node in zookeeper include the iterators.
  When the compaction count is incremented, iterators are also appended.   When a compaction
finishes, its iterators are removed from the compaction count.  This can be achieved safely
using the zookeeper compare and set mechanism for setting the count + iterators.  The tablet
server only has one node to read from zookeeper so there is no consistency issue. 
> Allow per compaction iterator settings
> --------------------------------------
>                 Key: ACCUMULO-420
>                 URL:
>             Project: Accumulo
>          Issue Type: New Feature
>            Reporter: Keith Turner
>            Assignee: Sapan Shah
>             Fix For: 1.5.0
> It may be useful to allow the compact command to specify an iterator to be used for that
compaction.  For example if someone wanted to apply a filter once to a table, they could force
a compaction with that filter.

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