run_machine: unknown connection (EventMachine::ConnectionNotBound)

[djensenius]

I'm running into this error a lot:

vendor/bundle/ruby/2.3.0/gems/eventmachine-1.2.5/lib/eventmachine.rb:194:in `run_machine': unknown connection: 312 (EventMachine::ConnectionNotBound)
    from vendor/bundle/ruby/2.3.0/gems/eventmachine-1.2.5/lib/eventmachine.rb:194:in `run'
    from bin/kafka-consumer:292:in `block in <top (required)>'

Exception reporting shows this coming from the EM.run line, but rescuing that does not catch anything and the error continues to be reported.

The theory is that this occurs during shutdown (we run EM in a background thread... maybe when the main thread exits this causes an issue?) when we're restarting anyway, so it isn't affecting us a lot but is super annoying and would like to understand more.

[alexandrule]

I also have this issue and trying to find a solution.
@djensenius Did you find a solution?

[karthikic]

+1
seeing this issue and its tad annoying

[sodabrew]

I cannot reproduce this myself. If you can post a small script that triggers this error, I'd be glad to run it down.

[abepetrillo]

I know this is an old bug but it's still open so...
We have regularly come across this when trying to do:

EventMachine.run do
end

This crashes pretty regularly on Heroku. Not sure if it matters but we call this code via sidekiq worker so:

require 'eventmachine'

class StartEventMachineWorker
  include Sidekiq::Worker

  sidekiq_options queue: :event_machine, retry: 12, backtrace: true

  def perform
    EventMachine.run do
    end
  end
end

Running the same code locally, this never happens.
Ruby version: 2.3.8 and 2.4.9
Eventmachine version: 1.2.7