How you are dealing with spikes?

Luke Bakken lbakken at basho.com
Tue Dec 9 09:46:04 EST 2014


Hi Alexander,

Can you comment on the read vs. write load of this cluster/

Could you please run the following command and reply with the output?

sysctl -a | fgrep vm.dirty_

We've seen cases where dirty pages get written in a synchronous manner
all at once, causing latency spikes due to I/O blocking.
--
Luke Bakken
Engineer / CSE
lbakken at basho.com


On Tue, Dec 9, 2014 at 4:58 AM, Alexander Popov <mogadanez at gmail.com> wrote:
> I have Riak 2.0.1 cluster with 5 nodes ( ec2 m3-large ) with elnm in front
> sometimes I got spikes  up to 10 seconds
>
> I can't say that I have  huge load at this time,  max 200 requests per
> second for all 5 nodes.
>
> Most expensive queries is
> * list by secondary index ( usually returns from 0 to 100 records  )
> * and solr queries( max 10 records )
>
> save operations  is slowdown sometimes but not so much ( up to 1 sec )
>
> It's slowdown not for specific requests, same one work pretty fast later.
>
> Does it any possibilities to profile|log somehow to determine reason
> why this happen?
>
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