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From Gregg Ulrich <gulr...@netflix.com>
Subject Re: how to stop out of control compactions?
Date Mon, 01 Apr 2013 22:12:17 GMT
You may want to set compaction threshold and not throughput.  If you set
the min threshold to something very large (100000), compactions will not
start until cassandra finds this many files to compact (which it should
not).

In the past I have used this to stop compactions on a node, and then run an
offline major compaction to get though the compaction, then set the min
threshold back.  Not everyone likes major compactions though.



  setcompactionthreshold <keyspace> <cfname> <minthreshold> <maxthreshold>
- Set the min and max
compaction thresholds for a given column family



On Mon, Apr 1, 2013 at 12:38 PM, William Oberman
<oberman@civicscience.com>wrote:

> I'll skip the prelude, but I worked myself into a bit of a jam.  I'm
> recovering now, but I want to double check if I'm thinking about things
> correct.
>
> Basically, I was in a state where a majority of my servers wanted to do
> compactions, and rather large ones.  This was impacting my site
> performance.  I tried nodetool stop COMPACTION.  I tried
> setcompactionthroughput=1.  I tried restarting servers, but they'd restart
> the compactions pretty much immediately on boot.
>
> Then I realized that:
> nodetool stop COMPACTION
> only stopped running compactions, and then the compactions would
> re-enqueue themselves rather quickly.
>
> So, right now I have:
> 1.) scripts running on N-1 servers looping on "nodetool stop COMPACTION"
> in a tight loop
> 2.) On the "Nth" server I've disabled gossip/thrift and turned up
> setcompactionthroughput to 999
> 3.) When the Nth server completes, I pick from the remaining N-1 (well,
> I'm still running the first compaction, which is going to take 12 more
> hours, but that is the plan at least).
>
> Does this make sense?  Other than the fact there was probably warning
> signs that would have prevented me from getting into this state in the
> first place? :-)
>
> will
>

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