Ran into some issues today with our Sidekiq/Statsd setup. We have a nice sidekiq middleware component that wraps each job in a "time" block; it works great.

The problem is that, under load, garbage collection does not get to run and all of the UDPSockets attached to threads are left behind.

To remedy this I added a tweak to the middleware to clean up the UDPSocket after the job finishes.

class StatsdMiddleware
  def call(worker, msg, queue)
    statsd = #get statsd however
    statsd.time("#{worker.class}.perform") do
      yield
    end
  ensure
    socket = Thread.current[:statsd_socket]
    socket.close if socket
    Thread.current[:statsd_socket] = nil
  end
end

This is then added into Sidekiq as a server middleware...

Sidekiq.configure_server do |config|
  config.server_middleware do |chain|
    chain.add StatsdMiddleware
  end
end

This may be applicable to other threading/forking situations like unicorn and passenger as well.

I could package this up as an optional class or something, not sure if that's going too far. If nothing else, a wiki page might be good.