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From "Aleksey Yeschenko (JIRA)" <>
Subject [jira] [Commented] (CASSANDRA-8573) Lack of compaction tooling for LeveledCompactionStrategy
Date Wed, 07 Jan 2015 16:14:35 GMT


Aleksey Yeschenko commented on CASSANDRA-8573:

Yep, that's an issue, but we are already on it.

See CASSANDRA-7272 and CASSANDRA-7019. There is already a patch available, even, and it'll
be part of 3.0.

> Lack of compaction tooling for LeveledCompactionStrategy
> --------------------------------------------------------
>                 Key: CASSANDRA-8573
>                 URL:
>             Project: Cassandra
>          Issue Type: Bug
>            Reporter: Jens Rantil
> This is a highly frustration-driven ticket. Apologize for roughness in tone ;-)
> *Background:* I happen to have a partition key with lots of tombstones. Sadly, I happen
to run LeveledCompactionStrategy (LCS). Yes, it's probably my mistake to have put them there
but running into tombstone issues seem to be common for Cassandra, so I don't think this ticket
can be discarded as simply user error. In fact, I believe this could happen to the best of
us. And when it does, there should be a quick way of correcting this.
> *Problem:* How does one handle this? Well, for DTCS one could issue a compaction using
`nodetool compact`, or one could use the forceUserDefinedCompaction MBean. Neither of these
work for LCS (shall I also say DTCS?).
> *Workaround:* The only options AFAIK are
>  1. to lower "gc_grace_seconds" and "wait it out" until the Cassandra node(s) has garbage
collected the sstables. This can take days.
>  2. possibly lower `tombstone_threshold` to something tiny, optionally lowering `tombstone_compaction_interval
` (for recent deletes). This has the implication that nodes might start garbage collecting
a ton of unrelated stuff.
>  3. variations of "delete some or all your sstables" and run a full repair. Takes ages.
> *Proposed solution:* Either
>  - Make forceUserDefinedCompaction support LCS, or create a similar endpoint that does
something similar.
>  - make something similar to `nodetool compact` work with LCS.
> *Additional comments:* I read somewhere where someone proposed making LCS default compaction
strategy. Before this ticket is fixed, I don't see that as an option.
> Let me know what you think (or close if not relevant).

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