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From "Benedict (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-7066) Simplify (and unify) cleanup of compaction leftovers
Date Tue, 09 Jun 2015 12:55:01 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-7066?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14578840#comment-14578840
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Benedict commented on CASSANDRA-7066:
-------------------------------------

bq. Regarding SSTableDeletingTask, I'll see if I can remove it.

Thanks.

bq.  Logging a descriptor would therefore be equivalent

There is a _slight_ difference in semantics that may be worth raising for posterity, which
is that the current logic (and the pre-existing logic) only deletes files we think _should_
be there, not any that are there by accident (or that we don't bookkeep properly, by including
in the set of expected files). I've always found it a bit confusing that we go to the effort
of calculating what files we expect, instead of just blindly deleting them all, since we want
them all gone either way. It's not a big thing, of course.


> 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
>
>         Attachments: 7066.txt
>
>
> 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or conversely not cleanup files that have been superceded); and 2) it's only used for a regular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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