Spawning daemon processes

Ruby
1

I am trying to start and stop a daemon process from inside my Ruby
program. At first I tried using fork to do the job, as in

server_pid = fork do
system ‘runserver’
end

Then I could use the returned PID to send the process a signal by
using Process.kill. But, as far as i know, fork unfortunately doesn’t
work on Windows. I read somewhere I should be using Thread.new if I
want the code to be platform independent, like this:

thread = Thread.new do
system ‘runserver’
end

The question is: how do I kill the subprocess when using threads? I
tried thread.kill and thread.stop, but they won’t do the trick. When
using threads, what I get are a lot of orphan processes after the
initial Ruby program finishes.

Is there any idiomatic way of doing that in Ruby that is platform
independent?

Cheers,

Thiago A.

2

On 8/31/06, Thiago A. [email protected] wrote:

I am trying to start and stop a daemon process from inside my Ruby
program. At first I tried using fork to do the job, as in

server_pid = fork do
system ‘runserver’
end

Then I could use the returned PID to send the process a signal by
using Process.kill.

For unix, you might want to check out the rubygem called ‘daemons’.
If you are not setup with rubygems, you could also download it from:

http://rubyforge.org/projects/daemons/

If what you are writing is meant to be a standard unix daemon, which
implies a number of things about how it should behave, then this
daemons package will handle many of the details that you might
not be aware of.

I only use the daemons package on unix, and I suspect that it does
not work on Windows.

But, as far as i know, fork unfortunately doesn’t work on Windows.

My guess is that you need to write your script to do one set of things
under Unix, and something else when it is run under WIndows.
But maybe someone else will have a useful solution for you.

3

On Fri, 1 Sep 2006, Thiago A. wrote:

Is there any idiomatic way of doing that in Ruby that is platform
independent?

I’d just use Daniel B.'s win32utils:

http://rubyforge.org/projects/win32utils/

You need win32-process (which needs windows-pr) out of there, and then
you
can easily use create_process on Windows. Here’s one way that I use it
to
provide a method for spawning new processes that works where fork exists
and on Windows, as well.

module IWATestSupport
def self.create_process(args)

Takes a hash with two keys, :cmd and :dir.

:cmd is the command to execute, and :dir is the directory to

execute the command from.

 args[:cmd] = [args[:cmd]] unless args[:cmd].is_a?(Array)
 @fork_ok = true unless @fork_ok == false
 pid = nil
 begin
   raise NotImplementedError unless @fork_ok
   unless pid = fork
     Dir.chdir args[:dir]
     exec(*args[:cmd])
   end
 rescue NotImplementedError
   @fork_ok = false
   begin
     require 'rubygems'
   rescue Exception
   end

   begin
     require 'win32/process'
   rescue LoadError
     raise "Please install win32-process.\n'gem install

win32-process’ or http://rubyforge.org/projects/win32utils"
end
cwd = Dir.pwd
Dir.chdir args[:dir]
pid = Process.create(:app_name => args[:cmd].join(’ '))
Dir.chdir cwd
end
pid
end
end

IWATestSupport.create_process({:dir => ‘TC_CGI_Adaptor’,
:cmd =>
[ruby,‘-I…/…/…/src’,‘webrick.rb’]})

There are a lot of very nice things in Dan’s win32utils.

Kirk H.

4

Kirk,

Thanks for pointer.

After some talking to Daniel, I could actually use his win32-process
library. It had a little bug that prevented it from being used under
Win2k, but he promptly fixed it.

Cheers,

Thiago A.

5

Thiago A. wrote:

[snip]
Thiago A.

Be careful … we don’t want to have Ruby known as “daemon spawn”, do
we?