CODEWITHSUNDEEP
ruby-on-railsrubydaemon
Jim Mitchener
Jim Mitchener

Reputation: 9003

Dynamic Ruby Daemon Management

I have a Ruby process that listens on a given device. I would like to spin up/down instances of it for different devices with a rails app. Everything I can find for Ruby daemons seems to be based around a set number of daemons running or background processing with message queues.

Should I just be doing this with Kernel.spawn and storing the PIDs in the database? It seems a bit hacky but if there isn't an existing framework that allows me to bring up/down daemons it seems I may not have much choice.

Upvotes: 0

Views: 296

Answers (1)

Mladen Jablanović
Mladen Jablanović

Reputation: 44080

Instead of spawning another script and keeping the PIDs in the database, you can do it all within the same script, using fork, and keeping PIDs in memory. Here's a sample script - you add and delete "worker instances" by typing commands "add" and "del" in console, exiting with "quit":

@pids = []
@counter = 0

def add_process
  @pids.push(Process.fork {
    loop do
      puts "Hello from worker ##{@counter}"
      sleep 1
    end
  })
  @counter += 1
end

def del_process
  return false if @pids.empty?
  pid = @pids.pop
  Process.kill('SIGTERM', pid)
  true
end

def kill_all
  while del_process
  end
end

while cmd = gets.chomp
  case cmd.downcase
  when 'quit'
    kill_all
    exit
  when 'add'
    add_process
  when 'del'
    del_process
  end
end

Of course, this is just an example, and for sending comands and/or monitoring instances you can replace this simple gets loop with a small Sinatra app, or socket interface, or named pipes etc.

Upvotes: 1

Related Questions