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From Guillermo Winkler <gwink...@inconcertcc.com>
Subject Re: Why the StageManager thread pools have 60 seconds keepalive time?
Date Fri, 17 Aug 2012 22:01:45 GMT
Aaron, thanks for your answer.

I'm actually tracking a problem where mutations get dropped and cfstats
show no activity whatsoever, I have 100 threads for the mutation pool, no
running or pending tasks, but some mutations get dropped none the less.

I'm thinking about some scheduling problems but not really sure yet.

Have you ever seen a case of dropped mutations with the system under light
load?

Thanks,
Guille


On Thu, Aug 16, 2012 at 8:22 PM, aaron morton <aaron@thelastpickle.com>wrote:

> That's some pretty old code. I would guess it was done that way to
> conserve resources. And _i think_ thread creation is pretty light weight.
>
> Jonathan / Brandon / others - opinions ?
>
> Cheers
>
>
>   -----------------
> Aaron Morton
> Freelance Developer
> @aaronmorton
> http://www.thelastpickle.com
>
> On 17/08/2012, at 8:09 AM, Guillermo Winkler <gwinkler@inconcertcc.com>
> wrote:
>
> Hi, I have a cassandra cluster where I'm seeing a lot of thread trashing
> from the mutation pool.
>
> MutationStage:72031
>
> Where threads get created and disposed in 100's batches every few minutes,
> since it's a 16 core server concurrent_writes is set in 100 in the
> cassandra.yaml.
>
> concurrent_writes: 100
>
> I've seen in the StageManager class this pools get created with 60 seconds
> keepalive time.
>
> DebuggableThreadPoolExecutor -> allowCoreThreadTimeOut(true);
>
> StageManager-> public static final long KEEPALIVE = 60; // seconds to keep
> "extra" threads alive for when idle
>
> Is it a reason for it to be this way?
>
> Why not have a fixed size pool with Integer.MAX_VALUE as keepalive since
> corePoolSize and maxPoolSize are set at the same size?
>
> Thanks,
> Guille
>
>
>

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