How to deploy a JRuby Resque process as a war file?

Question

I have a JRuby/Rails application which is deployed as a WAR file and run in the Tomcat application server. I would like to use either delayed_job or Resque as a tool to do long-running jobs which schlep through the database through the same ActiveRecord subclasses use by my Rails application. And I want it to run in a different process or thread so as not to make my web-facing side of the application seem slow.

The instructions to include and use delayed_job or Resque are pretty clear. For example, once I have done all of the jiggery-pokery to use Resque, I simply have to do:

QUEUE=* jruby -J-cp /path/to/library -S rake environment resque:work

But this only works from the command line. How do I get it so that my Resque process(es) can run by deploying a WAR file to Tomcat? If so, is it the same WAR file with a different configuration or a different WAR file? If it is a different WAR file, how do I generate it? Do I need a second Tomcat for the Resque/DJ process? Is there a way to put the Resque/DJ process into its own JRuby/JVM thread? Is there any configuration jiggery-pokery I must do to get this going?

Answer 1

JRuby does recognize shell commands whose ARGV[0] =~ /ruby$/ and run them in-process, so you could use this to your advantage. Assuming you include your Rakefile in your war file, you could start a thread and launch Resque in it with a similar command from an application initializer. If you're using Bundler, it will already have the environment set up and it should be passed to the in-process child JRuby.