Workaround for JRuby's timeout not working well with IO.popen

jruby_timeout.rb

# Workaround for IO.popen.readlines being allowed to block indefinitely even if
# wrapped in a Timeout::timeout call.
#
# Test case:
#  $ time jruby -rtimeout -e "timeout(1) { IO.popen('sleep 10').readlines }"
require 'jruby'

module Timeout
  def self.timeout(sec, klass=nil)
    return yield(sec) if sec == nil or sec.zero?
    thread = Thread.new { yield(sec) }

    if thread.join(seconds).nil?
      java_thread = JRuby.reference(thread)
      thread.kill
      java_thread.native_thread.interrupt
      thread.join(0.15)
      raise (klass || Error), 'execution expired'
    else
      thread.value
    end
  end
end

include Timeout

Thank you so much for this! Fixes timeout for me in a case where it wasn't working. I had to change seconds on line 13 to sec.

Did you file a bug with the JRuby team?

The test case provided appears to work fine with JRuby master (9000) which has reimplemented process-launching. I'll see if there's anything that can be done with the interrupt logic on 1.7.x.

Note: one problem with the above hack is that interrupting a blocking Java IO read (as is happening here) generally closes the underlying stream and it can no longer be used. That's why we've gone back and forth on whether to do a hard Thread interrupt or just block.