Module: Sqewer::CLI

Extended by:
CLI
Included in:
CLI
Defined in:
lib/sqewer/cli.rb

Overview

Wraps a Worker object in a process-wide commanline handler. Once the start method is called, signal handlers will be installed for the following signals:

  • TERM, USR1 - will soft-terminate the worker (let all the threads complete and die)
  • KILL - will hard-kill all the threads
  • INFO - will print backtraces and variables of all the Worker threads to STDOUT

Instance Method Summary collapse

Instance Method Details

#handle_signal(worker, sig) ⇒ Object 



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# File 'lib/sqewer/cli.rb', line 38

def handle_signal(worker, sig)
  case sig
  when 'USR1', 'TERM'
    worker.stop
    exit 0
  when 'INFO' # a good place to print the worker status
    worker.debug_thread_information!
  else
    raise Interrupt
  end
end

#start(worker = Sqewer::Worker.default) ⇒ void

This method returns an undefined value.

Start the commandline handler, and set up a centralized signal handler that reacts to USR1 and TERM to do a soft-terminate on the worker.

Parameters:

  • worker (Sqewer::Worker) (defaults to: Sqewer::Worker.default) —

    the worker to start. Must respond to #start and #stop



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# File 'lib/sqewer/cli.rb', line 13

def start(worker = Sqewer::Worker.default)
  # Use a self-pipe to accumulate signals in a central location
  self_read, self_write = IO.pipe
  %w(INT TERM USR1 USR2 INFO TTIN).each do |sig|
    begin
      trap(sig) { self_write.puts(sig) }
    rescue ArgumentError
      # Signal not supported
    end
  end

  begin
    worker.start
    # The worker is non-blocking, so in the main CLI process we select() on the signal
    # pipe and handle the signal in a centralized fashion
    while (readable_io = IO.select([self_read]))
      signal = readable_io.first[0].gets.strip
      handle_signal(worker, signal)
    end
  rescue Interrupt
    worker.stop
    exit 1
  end
end