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Unicorn.rb for configuration
worker_processes 3 # amount of unicorn workers to spin up
timeout 30 # restarts workers that hang for 30 seconds
preload_app true
GC.respond_to?(:copy_on_write_friendly=) and
GC.copy_on_write_friendly = true
before_fork do |server,worker|
defined?(ActiveRecord::Base) and
after_fork do |server,worker|
defined?(ActiveRecord::Base) and
if defined?(EventMachine)
unless EventMachine.reactor_running? && EventMachine.reactor_thread.alive?
if EventMachine.reactor_running?
end { }
Signal.trap("INT") { EventMachine.stop }
Signal.trap("TERM") { EventMachine.stop }

I'm using this on Heroku and occasionally seeing this error: An EventMachine loop must be running to use publish_async calls.

Have you seen anything like this? I assume that for some reason the EventMachine crashed but the dyno remained alive. Do you have any suggestions for how to handle that case? Could I restart the EventMachine from inside one of my unicorn forks?


I have also seen the same error. Did you find a solution? Also, do you see this: Error R12 (Exit timeout) -> At least one process failed to exit within 10 seconds of SIGTERM

This only started happening after I added this code.


The issues commented above were solved ? If yes, how ? Thanks in advance.


To @arches - it is possible that EM can crash while the dyno still is up (even when EM is restarted after forks). A quick way to avoid this is to ensure the loop is running before each call:

def ensure_em
  unless EventMachine.reactor_running? && EventMachine.reactor_thread.alive? { }
    sleep 1

# put this before calls

To @elihuu - hard to say what that might be. It could be a stray event loop, but stop should be getting called. If something is going wrong in the event loop, you might be able to find it by registering a global error handler.

EventMachine.error_handler{ |e|
  puts "Error raised during event loop: #{e.message}"


Above configuration works great for Unicorn + EventMachine, but every time either new deploy or restart heroku process, it prints out a lot of errors in the log


Same issue with Heroku here.


Same thing here with Heroku + Rails


WARNING: Detected 2 Thread(s) started in app boot:
2015-03-26T00:07:54.952008+00:00 app[web.1]: [3] ! # - /app/vendor/bundle/ruby/2.1.0/gems/newrelic_rpm- select'
2015-03-26T00:07:54.952030+00:00 app[web.1]: [3] ! #<Thread:0x007f020ac92cb0 sleep> - /app/vendor/bundle/ruby/2.1.0/gems/eventmachine-1.0.7/lib/eventmachine.rb:187:in

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