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From "Joshua McKenzie (JIRA)" <>
Subject [jira] [Commented] (CASSANDRA-7066) Simplify (and unify) cleanup of compaction leftovers
Date Fri, 20 Feb 2015 16:54:11 GMT


Joshua McKenzie commented on CASSANDRA-7066:

I much prefer the idea of us building a simple custom abstraction that handles our view of
the state of sstable deletion rather than an amalgamation of system tables + file names or
parsing ancestor sets in sstable metadata - both of those options sound overly complex to
address the question of "are we done with this sstable?".

>From a Windows perspective, I'm immediately in favor of limiting any renaming we do on
grounds of ntfs being picky about that.

What you're proposing, [~benedict], sounds easier to reason about, more simple, and more elegant
than the other options. I'm in favor.

> Simplify (and unify) cleanup of compaction leftovers
> ----------------------------------------------------
>                 Key: CASSANDRA-7066
>                 URL:
>             Project: Cassandra
>          Issue Type: Improvement
>          Components: Core
>            Reporter: Benedict
>            Priority: Minor
>              Labels: compaction
>             Fix For: 3.0
> 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or conversely not cleanup files that have been superceded); and 2) it's only used for a regular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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