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 <[email protected]> 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 <[email protected]> > 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 <[email protected]> >> 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 <[email protected]> >>> 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 <[email protected]> >>>> 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 <[email protected]> >>>>> 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* >>>>>> [email protected] >>>>>> >>>>>> >>>>>> >>>>> >>>> >>>> >>>> -- >>>> *Sarkis Varozian* >>>> [email protected] >>>> >>> >>> >> >> >> -- >> *Sarkis Varozian* >> [email protected] >> > > -- *Sarkis Varozian* [email protected]
