[jira] [Commented] (CASSANDRA-5151) Implement better way of eliminating compaction left overs.

["Yuki Morishita (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-5151?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13556392#comment-13556392 ] 

Yuki Morishita commented on CASSANDRA-5151:
-------------------------------------------

We want to remove left-overs before opening CFs by reading compaction log system CF. The problem is, commit log has to be recovered before reading from any CF, but CF initialization should be completed before commit log recovery. So there is no chance to scrub off left-overs before CF init. Obviously we don't want to flush every time we update compaction log.

Alternative way is to write compaction log file with inputs each time we start compaction, and remove it when complete.
If CF sees that compaction log files in its data directory, that means there are unfinished compactions and those sstable files with ancestors that are in compaction log files should be deleted. Does this sound likely to work?
                
> Implement better way of eliminating compaction left overs.
> ----------------------------------------------------------
>
>                 Key: CASSANDRA-5151
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-5151
>             Project: Cassandra
>          Issue Type: Bug
>    Affects Versions: 1.1.3
>            Reporter: Yuki Morishita
>             Fix For: 1.2.1
>
>
> This is from discussion in CASSANDRA-5137. Currently we skip loading SSTables that are left over from incomplete compaction to not over-count counter, but the way we track compaction completion is not secure.
> One possible solution is to create system CF like:
> {code}
> create table compaction_log (
>   id uuid primary key,
>   inputs set<int>,
>   outputs set<int>
> );
> {code}
> to track incomplete compaction.

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