Gemfile

source "https://rubygems.org"

ruby "1.9.3", engine: "jruby", engine_version: "1.7.23"

gem "celluloid-io"

issue.rb

require "celluloid/io"

class Issue
  include Celluloid::IO

  def initialize
    every(0.1) { puts "WORKING #{Time.now.to_i}" }
  end
end

client = Issue.new
sleep

issue_with_io.rb

require "celluloid/current"
require "celluloid/io"

class IssueWithIO
  include Celluloid::IO

  def initialize(host, port)
    puts "Connecting server on #{host}:#{port}"
    @socket = TCPSocket.new(host, port)

    async.run
  end

  def send_data(data)
    @socket.write([999, data.bytesize].pack("CL"))
    @socket.write(data)
  end

  def listen
    loop do
      @socket.readpartial(4096)
      puts "GOT A MESSAGE! #{Time.now.to_i}"
    end
  end

  def run
    async.listen
    every(1) do
      send_data "HELLO CELLULOID #{Time.now.to_i}"
    end
  end
end

supervisor = IssueWithIO.new("0.0.0.0", 5000)
sleep

no_issue.rb

require "celluloid"

class Issue
  include Celluloid

  def initialize
    every(0.1) { puts "WORKING #{Time.now.to_i}" }
  end
end

client = Issue.new
sleep

Works on MRI 2.2.3
Does not work on JRuby 1.7.23

~ bundle exec ruby issue.rb 
I, [2015-12-06T13:43:28.321000 #28450]  INFO -- : Celluloid 0.17.2 is running in BACKPORTED mode. [ http://git.io/vJf3J ]
WORKING 1449431009
WORKING 1449431009
WORKING 1449431009
WORKING 1449431009
WORKING 1449431009
WORKING 1449431009
WORKING 1449431009
WORKING 1449431009
WORKING 1449431009
WORKING 1449431010
WORKING 1449431010
WORKING 1449431010
WORKING 1449431010
WORKING 1449431010
WORKING 1449431010
WORKING 1449431010
WORKING 1449431010
WORKING 1449431010
WORKING 1449431010
WORKING 1449431011
WORKING 1449431011

Then hangs indefinitely

Interestingly, including Celluloid and not Celluloid::IO, this example runs fine.

@jsonperl when you use Celluloid::IO there is expected to be I/O involved, especially some kind of network traffic that would normally be "blocking" and is instead "evented" ... which creates back-pressure. I'd imagine you're having issues because the example code is intended to work with Celluloid and not need Celluloid::IO at all, because it has no I/O. Granted, your example should at least show an error if it doesn't work, or just work -- but it'd make sense that the jRuby I/O selector has no activity going on.

@digitalextremist first off, thanks so much for responding quickly, and for the help. I really appreciate it.

The example provided was as minimal as I could make to demonstrate the issue. I've added another minimal(ish) example exhibiting the exact same behavior, but with IO involved: issue_with_io.rb. Again, works fine in MRI, and sends data successfully to the server, but hangs very quickly with JRuby.