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From "Stefania (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-7066) Simplify (and unify) cleanup of compaction leftovers
Date Fri, 01 May 2015 09:54:06 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-7066?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14522998#comment-14522998
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Stefania commented on CASSANDRA-7066:
-------------------------------------

To give more context you can look at the usages of desc.type.isTemporary, for example in SSTableLoader.openSSTables,
CFS.loadNewSSTables(), CFS.scrubDataDirectories() and Directories.SSTableLister.

I'm not necessarily against it but before I go ahead and remove temporary desc types I want
to be absolutely sure this is 100% OK.

To replayce desc.type.isTemporary we have to look for any transaction logs for the CF, read
the list of files from these logs and see if the file name is one of them. It's fine as long
as the transaction logs can be found, else we may end up loading incomplete or corrupt files.

> Simplify (and unify) cleanup of compaction leftovers
> ----------------------------------------------------
>
>                 Key: CASSANDRA-7066
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-7066
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Benedict
>            Assignee: Stefania
>            Priority: Minor
>              Labels: compaction
>             Fix For: 3.x
>
>
> Currently we manage a list of in-progress compactions in a system table, which we use
to cleanup incomplete compactions when we're done. The problem with this is that 1) it's a
bit clunky (and leaves us in positions where we can unnecessarily cleanup completed files,
or conversely not cleanup files that have been superceded); and 2) it's only used for a regular
compaction - no other compaction types are guarded in the same way, so can result in duplication
if we fail before deleting the replacements.
> I'd like to see each sstable store in its metadata its direct ancestors, and on startup
we simply delete any sstables that occur in the union of all ancestor sets. This way as soon
as we finish writing we're capable of cleaning up any leftovers, so we never get duplication.
It's also much easier to reason about.



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