On Mon, 10 Sep 2018, 19:29 Charulata Sharma (charshar), <chars...@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.shul...@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 > > >
