Re: Request Queueing after deploy + USR2 restart

[Michael Fischer <mfischer@zendesk.com>]

What does your I/O latency look like during this interval?  (iostat -xk 10,
look at the busy %).  I'm willing to bet the request queueing is strongly
correlated with I/O load.

Also is preload_app set to true?  This should help.

--Michael

On Wed, Mar 4, 2015 at 11:48 AM, Sarkis Varozian <svarozian@gmail.com>
wrote:

> Michael,
>
> Thanks for this - I have since changed the way we are restarting the
> unicorn servers after a deploy by changing capistrano task to do:
>
> in :sequence, wait: 30
>
> We have 4 backends and the above will restart them sequentially, waiting
> 30s (which I think should be more than enough time), however, I still get
> the following latency spikes after a deploy: http://goo.gl/tYnLUJ
>
> This is what the individual servers look like for the same time interval:
> http://goo.gl/x7KcKq
>
>
>
> On Tue, Mar 3, 2015 at 2:32 PM, Michael Fischer <mfischer@zendesk.com>
> wrote:
>
>> If the response times are falling a minute or so after the reload, I'd
>> chalk it up to a cold CPU cache.  You will probably want to stagger your
>> reloads across backends to minimize the impact.
>>
>> --Michael
>>
>> On Tue, Mar 3, 2015 at 2:24 PM, Sarkis Varozian <svarozian@gmail.com>
>> wrote:
>>
>>> We have a rails application with the following unicorn.rb:
>>> http://goo.gl/qZ5NLn
>>>
>>> When we deploy to the application, a USR2 signal is sent to the unicorn
>>> master which spins up a new master and we use the before_fork in the
>>> unicorn.rb config above to send signals to the old master as the new
>>> workers come online.
>>>
>>> I've been trying to debug a weird issue that manifests as "Request
>>> Queueing" in our Newrelic APM. The graph shows what happens after a
>>> deployment (represented by the vertical lines). Here is the graph:
>>> http://goo.gl/iFZPMv . As you see from the graph, it is inconsistent -
>>> there is always a latency spike - however, at times Request Queueing is
>>> higher than previous deploys.
>>>
>>> Any ideas on what exactly is going on here? Any suggestions on
>>> tools/profilers to use to get to the bottom of this? Should we expect
>>> this
>>> to happen on each deploy?
>>>
>>> Thanks,
>>>
>>> --
>>> *Sarkis Varozian*
>>> svarozian@gmail.com
>>>
>>>
>>>
>>
>
>
> --
> *Sarkis Varozian*
> svarozian@gmail.com
>