Re: Request Queueing after deploy + USR2 restart

[Sarkis Varozian <svarozian@gmail.com>]

Yes, preload_app is set to true, I have not made any changes to the
unicorn.rb from OP: http://goo.gl/qZ5NLn

Hmmmm, you may be onto something - Here is the i/o metrics from the server
with the highest response times: http://goo.gl/0HyUYt (in this graph:
http://goo.gl/x7KcKq)

Looks like it may be i/o related as you suspect - is there much I can do to
alleviate that?

On Wed, Mar 4, 2015 at 11:51 AM, Michael Fischer <mfischer@zendesk.com>
wrote:

> 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
>>
>
>


-- 
*Sarkis Varozian*
svarozian@gmail.com