Thank for your help, Eric. I was able to pinpoint the issue, and I've posted the solution.
The issue was that I wasn't closing a database connection for code being run in custom Rack middleware. Which is why the logs didn't show anything. http://serverfault.com/questions/655430/unicorn-workers-timing-out-intermittently/655478#655478 Thanks again. On Tue, Dec 30, 2014 at 1:12 PM, Eric Wong <[email protected]> wrote: > Aaron Price <[email protected]> wrote: > > Hey guys, > > > > I'm having the following issue and I was hoping you might be able to shed > > some light on the issue. Maybe give some suggestions on how to debug the > > actual problem. > > > > > http://serverfault.com/questions/655430/unicorn-workers-timing-out-intermittently > > (quoting the problem in full to save folks from having to load the page) > > > I'm getting intermittent timeouts from unicorn workers for seemingly > no > > reason, and I'd like some help to debug the actual problem. It's worse > > because it works about 10 - 20 requests then 1 will timeout, then > > another 10 - 20 requests and the same thing will happen again. > > > > I've created a dev environment to illustrate this particular problem, > > so there is NO traffic except mine. > > > > The stack is Ubuntu 14.04, Rails 3.2.21, PostgreSQL 9.3.4, Unicorn > > 4.8.3, Nginx 1.6.2. > > > > The Problem > > > > I'll describe in detail the time that it doesn't work. > > > > I request a url through the browser. > > Started GET > "/offers.xml?q%5bupdated_at_greater_than_or_equal_to%5d=2014-12-28T1 > > 8:01:16Z&q%5bupdated_at_less_than_or_equal_to%5d=2014-12-28T19:30:21Z" > for 127.0 > > .0.1 at 2014-12-30 15:58:59 +0000 > > Completed 200 OK in 10.3ms (Views: 0.0ms | ActiveRecord: 2.1ms) > > > > As you can see, the request completed successfully with a 200 response > > status in just 10.3ms. > > > > However, the browser hangs for about 30 seconds and Unicorn kills the > > worker: > > E, [2014-12-30T15:59:30.267605 #13678] ERROR -- : worker=0 PID:14594 > timeout (31 > > s > 30s), killing > > E, [2014-12-30T15:59:30.279000 #13678] ERROR -- : reaped > #<Process::Status: pid > > 14594 SIGKILL (signal 9)> worker=0 > > I, [2014-12-30T15:59:30.355085 #23533] INFO -- : worker=0 ready > > > > And the following error in the Nginx logs: > > 2014/12/30 15:59:30 [error] 23463#0: *27 upstream prematurely closed > connection > > while reading response header from upstream, client: 127.0.0.1, server: > localhos > > t, request: "GET > /offers.xml?q%5bupdated_at_greater_than_or_equal_to%5d=2014-12- > > > 28T18:01:16Z&q%5bupdated_at_less_than_or_equal_to%5d=2014-12-28T19:30:21Z > HTTP/1 > > .1", upstream: "http://unix: > /app/shared/tmp/sockets/unicorn.sock:/offers.xml?q%5 > > > bupdated_at_greater_than_or_equal_to%5d=2014-12-28T18:01:16Z&q%5bupdated_at_less > > _than_or_equal_to%5d=2014-12-28T19:30:21Z", host: "localhost", referrer: > "http:/ > > > /localhost/offers.xml?q%5bupdated_at_greater_than_or_equal_to%5d=2014-12-28T18:0 > > 1:16Z&q%5bupdated_at_less_than_or_equal_to%5d=2014-12-28T19:30:21Z" > > OK, the problem should be reproducible hitting unicorn directly (easy to > configure a TCP listener) and eliminating nginx as a possible > point-of-failure. Also, I suggest using curl so you can script and see > everything going on more easily at the protocol/syscall level. > > > Again. There's no load on the server at all. The only requests going > > through are my own and every 10 - 20 requests at random have this same > > problem. > > OK, the main culprit is usually external connections acting up. Postgres, > external monitoring services, network failures, etc... > > > It doesn't look like unicorn is eating memory at all. I know this > > because I'm using watch -n 0.5 free -m and this is the result. > > What does the CPU usage look like? > > > total used free shared buffers cached > > Mem: 1995 765 1229 0 94 405 > > -/+ buffers/cache: 264 1730 > > Swap: 511 0 511 > > > > So the server isn't running out of memory. > > > > Is there anything further I can do to debug this issue? or any insight > > into what's happening? > > Basically, minimize and isolate things. Use a single worker, strace > that worker ("strace -f -p $PID_OF_WORKER") and send a request to it > using curl. > > Is the Postgres doing OK? How is the network connection to that? > What other external resources (monitoring services, memcached, redis, > etc...) might you be hitting? You'll see blocking (on things like > read*/write*/select/poll/recvmsg/sendmsg) on strace. > > You can map numeric file descriptors to ports via: > lsof -p $PID_OF_WORKER > > Also, is your server running out of entropy? (You'll see blocking on > reading /dev/random via strace) and you may also see low values in > /proc/sys/kernel/random/entropy_avail > -- *Aaron Price* Sr. Web Developer FlipGive P: (416) 583-2510 312 Adelaide St. West, Suite 301 Toronto, ON, M5V 1R2 www.flipgive.com Follow us on: Facebook <http://www.facebook.com/FlipGive> | Twitter <http://twitter.com/FlipGive> | LinkedIn <http://www.linkedin.com/company/FlipGive>
