Re: Request Queueing after deploy + USR2 restart

[Sarkis Varozian <svarozian@gmail.com>]

Hey All,

So I changed up my unicorn.rb a bit from my original post:
https://gist.github.com/sarkis/1aa296044b1dfd3695ab

I'm also still sending the USR2 signals on deploy staggered with 30 second
delay via capistrano:

on roles(:web), in: :sequence, wait: 30

As you can see I am now doing a warup via rack MockRequest (I hoped this
would warmup the master). However, this is what a deploy looks like on
newrelic:

https://www.dropbox.com/s/beh7nc8npdfijqp/Screenshot%202015-03-05%2009.05.15.png?dl=0

https://www.dropbox.com/s/w08gpvp7mpik3vs/Screenshot%202015-03-05%2009.06.51.png?dl=0

I'm running out of ideas to get rid of thse latency spikes. Would you guys
recommend I try anything else at this point?



On Wed, Mar 4, 2015 at 12:40 PM, Sarkis Varozian <svarozian@gmail.com>
wrote:

> Eric,
>
> Thanks for the quick reply.
>
> We are on Ruby 2.1.5p273 and unicorn 4.8.3. I believe our problem is the
> lazy loading - at least thats what all signs point to. I am going to try
> and mock request some url endpoints. Currently, I can only think of '/', as
> most other parts of the app require a session and auth. I'll report back
> with results.
>
>
>
> On Wed, Mar 4, 2015 at 12:35 PM, Eric Wong <e@80x24.org> wrote:
>
>> Sarkis Varozian <svarozian@gmail.com> wrote:
>> > 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?
>>
>> (top-posting corrected)
>>
>> Yeah, preload_app won't help startup speed if much of the app is
>> autoloaded.
>>
>> Sarkis: which Ruby version are you running?  IIRC, 1.9.2 had terrible
>> startup performance compared to 1.9.3 and later in case you're stuck on
>> 1.9.2
>>
>> > 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 preload_app is true, you can warmup in before_fork; otherwise it
>> needs to be 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...
>>
>> With preload_app and warmup, you need to ensure any stream connections
>> (DB, memcached, redis, etc..) do not get shared between processes, so
>> it's standard practice to disconnect in the parent and reconnect in the
>> child.
>>
>> > 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?
>>
>> I've been leaving killing the master outside of the unicorn hooks
>> and doing it as a separate step; seemed too fragile to do it in
>> hooks from my perspective.
>>
>
>
>
> --
> *Sarkis Varozian*
> svarozian@gmail.com
>



-- 
*Sarkis Varozian*
svarozian@gmail.com