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From Oleksandr Shulgin <oleksandr.shul...@zalando.de>
Subject Re: Drop TTLd rows: upgradesstables -a or scrub?
Date Mon, 10 Sep 2018 17:35:06 GMT
On Mon, 10 Sep 2018, 19:29 Charulata Sharma (charshar),
<charshar@cisco.com.invalid> wrote:

> Scrub takes a very long time and does not remove the tombstones.
>
Charu,

Why is that if the documentation clearly says it does?

> should do garbage cleaning. It immediately removes the tombstones.
>
If you mean 'nodetool garbagecollect' - that command is not available in
the version we are using. It only became available in 3.10.

--
Alex

>
> *From: *Oleksandr Shulgin <oleksandr.shulgin@zalando.de>
> *Reply-To: *"user@cassandra.apache.org" <user@cassandra.apache.org>
> *Date: *Monday, September 10, 2018 at 6:53 AM
> *To: *"user@cassandra.apache.org" <user@cassandra.apache.org>
> *Subject: *Drop TTLd rows: upgradesstables -a or scrub?
>
>
>
> Hello,
>
>
>
> We have some tables with significant amount of TTLd rows that have expired
> by now (and more gc_grace_seconds have passed since the TTL).  We have
> stopped writing more data to these tables quite a while ago, so background
> compaction isn't running.  The compaction strategy is the default
> SizeTiered one.
>
>
>
> Now we would like to get rid of all the droppable tombstones in these
> tables.  What would be the approach that puts the least stress on the
> cluster?
>
>
>
> We've considered a few, but the most promising ones seem to be these two:
> `nodetool scrub` or `nodetool upgradesstables -a`.  We are using Cassandra
> version 3.0.
>
>
>
> Now, this docs page recommends to use upgradesstables wherever possible:
> https://docs.datastax.com/en/cassandra/3.0/cassandra/tools/toolsScrub.html
>
> What is the reason behind it?
>
>
>
> From source code I can see that Scrubber the class which is going to drop
> the tombstones (and report the total number in the logs):
> https://github.com/apache/cassandra/blob/cassandra-3.0/src/java/org/apache/cassandra/db/compaction/Scrubber.java#L308
>
>
>
> I couldn't find similar handling in the upgradesstables code path.  Is the
> assumption correct that this one will not drop the tombstone as a side
> effect of rewriting the files?
>
>
>
> Any drawbacks of using scrub for this task?
>
>
>
> Thanks,
> --
>
> Oleksandr "Alex" Shulgin | Senior Software Engineer | Team Flux | Data
> Services | Zalando SE | Tel: +49 176 127-59-707
>
>
>

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