Error R12 (Exit timeout) using Heroku's recommended Unicorn config

Question

My Unicorn config (copied from Heroku's docs):

# config/unicorn.rb
worker_processes Integer(ENV["WEB_CONCURRENCY"] || 3)
timeout 30
preload_app true

before_fork do |server, worker|
  Signal.trap 'TERM' do
    puts 'Unicorn master intercepting TERM and sending myself QUIT instead'
    Process.kill 'QUIT', Process.pid
  end

  defined?(ActiveRecord::Base) and
    ActiveRecord::Base.connection.disconnect!
end 

after_fork do |server, worker|
  Signal.trap 'TERM' do
    puts 'Unicorn worker intercepting TERM and doing nothing. Wait for master to send QUIT'
  end

  defined?(ActiveRecord::Base) and
    ActiveRecord::Base.establish_connection
end

But every time a dyno is restarted, we get this:

heroku web.5 - - Error R12 (Exit timeout) -> At least one process failed to exit within 10 seconds of SIGTERM

Ruby 2.0, Rails 3.2, Unicorn 4.6.3

Answer 1

I hate to add another answer, especially one this simple, but ultimately what fixed this problem for us was removing the 'rack-timeout' gem. I realize this is probably not best practice but I'm curious if there is some conflict between rack-timeout and Unicorn and/or Puma (which is odd because Heroku recommends rack-timeout for use with Unicorn).

Anyway Puma is working great for us but we did still see some random inexplicable timeouts even after the Puma upgrade . . . but removing rack-timeout got rid of the issue completely. Obviously we still get timeouts but only for code we haven't optimized or if we are getting heavy usage (basically when you would expect to see timeouts). Thus I would blame this issue on rack-timeout and not on Unicorn . . . thus contradicting my previous answer :)

Hope this helps. If anyone else wants to poke holes in my theory, feel free!