Question

I’ve got this script, that uploads some files, connects via ssh and does some stuff on the remote server, kinda like deployment script, and I want to make it run whenever I want to and to be able to reset it in the middle of processing.

def deploy
  # some stuff happens here
end

def do_deploy
   $deploy.kill! if $deploy
   $deploy = Thread.new { deploy }
   $deploy.join  # when I don't have the join here, it stop executing the deploy
                 # like after first when thread switches to something else, and
                 # then never finishes
end

reading = Thread.new do
  while line = gets.chomp!
    case line
    when "q" then
      puts "exiting"
      Thread.exit
      exit
    when "r" then
      do_deploy
    end
  end
end

reading.join

Even though the $deploy.join makes the whole deploy thread execute, it prevents reading any input, so I can’t reset it in the middle of execution. And I can’t join it at the end of the script.

What I essentially need to do, is to run a task while listening for an input and be able to kill the process and restart it at any given time. Or even better, send it a message that would get processed immediately, like shut down test execution.

I know that killing threads isn’t really a neat thing to do, but in this case, I don’t think that it’s a big issue.

I’d also like to point out, that I’m working on Windows, so I don’t have fork() available.

Is there any other way how to solve this without threads?

edit: Just found out, that calling gets blocks all other Threads from execution until any input is given. In this example

t1 = Thread.new { 10.times { |i| puts i } }
t2 = Thread.new { puts gets }
t1.join
t2.join

the t1 doesn’t get executed untill I give some input to the gets. It just keeps sitting there forever. How should I read from input without blocking all threads?

edit2: just found out, that this is a Windows related issue

edit3: the problem goes away in JRuby or Ruby 1.9

Answer 1

Use JRuby. It has real threads and doesn’t fall prey to the GIL (Global Interpreter Lock) that the C Ruby interpreter has.

http://www.jruby.org/