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From: Sarkis Varozian <svarozian@gmail.com>
To: Michael Fischer <mfischer@zendesk.com>
Cc: unicorn-public <unicorn-public@bogomips.org>
Subject: Re: Request Queueing after deploy + USR2 restart
Date: Wed, 4 Mar 2015 12:24:32 -0800	[thread overview]
Message-ID: <CAGchx-JUBAcaRwaMknZF+rtB+3dTZ+1jQUw5H1Nb=8YmFQRaBg@mail.gmail.com> (raw)
In-Reply-To: <CABHxtY79JHQ-Ba4tFNY5ZUDRzG-Y5NvCowXK6XCsi6rH_eScZQ@mail.gmail.com>

That does make sense - I was looking at another suggestion from a user here
(Braulio) of running a "warmup" using rack MockRequest:
https://gist.github.com/brauliobo/11298486#file-unicorn-conf-rb-L77

The only issue I am having with the above solution is it is happening in
the before_fork block - shouldn't I warmup the connection in after_fork? If
I follow the above gist properly it warms up the server with the old
activerecord base connection and then its turned off, then turned back on
in after_fork. I think I am not understanding the sequence of events
there... If this is the case, I should warmup and also check/kill the old
master in the after_fork block after the new db, redis, neo4j connections
are all created. Thoughts?

On Wed, Mar 4, 2015 at 12:17 PM, Michael Fischer <mfischer@zendesk.com>
wrote:

> I'm not exactly sure how preload_app works, but I suspect your app is
> lazy-loading a number of Ruby libraries while handling the first few
> requests that weren't automatically loaded during the preload process.
>
> Eric, your thoughts?
>
> --Michael
>
> On Wed, Mar 4, 2015 at 11:58 AM, Sarkis Varozian <svarozian@gmail.com>
> wrote:
>
>> 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
>>
>
>


-- 
*Sarkis Varozian*
svarozian@gmail.com


  reply	other threads:[~2015-03-04 20:24 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-03-03 22:24 Sarkis Varozian
2015-03-03 22:32 ` Michael Fischer
2015-03-04 19:48   ` Sarkis Varozian
2015-03-04 19:51     ` Michael Fischer
2015-03-04 19:58       ` Sarkis Varozian
2015-03-04 20:17         ` Michael Fischer
2015-03-04 20:24           ` Sarkis Varozian [this message]
2015-03-04 20:27             ` Michael Fischer
2015-03-04 20:35             ` Eric Wong
2015-03-04 20:40               ` Sarkis Varozian
2015-03-05 17:07                 ` Sarkis Varozian
2015-03-05 17:13                   ` Bráulio Bhavamitra
2015-03-05 17:28                     ` Sarkis Varozian
2015-03-05 17:31                       ` Bráulio Bhavamitra
2015-03-05 17:32                       ` Bráulio Bhavamitra
2015-03-05 21:12                       ` Eric Wong
2015-03-03 22:47 ` Bráulio Bhavamitra
2015-03-04 19:50   ` Sarkis Varozian
     [not found] ` <CAJri6_vidE15Xor4THzQB3uxyqPdApxHoyWp47NAG8m8TQuw0Q@mail.gmail.com>
2015-09-13 15:12   ` Bráulio Bhavamitra
2015-09-14  2:14     ` Eric Wong

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