demodblogger.rb

#!/usr/bin/env ruby
#
# ./script/demodblogger
#
# Designed to assist with running a command in the background and capturing
# its output as it runs, this script takes a demo id, and calls
# @demo.job_log(line) for each line given it on stdin. Run without arguments for a
# brief summary of usage.
#

options = {}

case ARGV.length
when 0..2 
  abort "Usage: ./script/demodblogger <environment> <demo_id> somecommand --args"
else
  options[:environment] = ARGV.shift
  options[:demo_id] = Integer(ARGV.shift)
  options[:command] = ARGV
end

if options[:environment]
  ENV["RAILS_ENV"] = options[:environment]
  RAILS_ENV.replace( options[:environment] ) if defined?(RAILS_ENV)
end

require File.dirname(__FILE__) + '/../config/environment'

class DBLogger
  
  def initialize( demo )
    @demo = demo
  end
  
  def log( msg, stream )
    @demo.job_log msg.rstrip, stream
  end
    
end

require 'open4'
require 'stringio'

begin
  # Try and open the command, logging stdout and stderr as you go.
  @demo = Demo.find(options[:demo_id])
  @dblogger = DBLogger.new(@demo)
  @log = Queue.new
    
  producer = Thread.new do
    @status = Open4.spawn( options[:command],
                           :stdin => STDIN.read,
                           :stdout => @log, 
                           :stderr => @log,
                           :exitstatus => true )
  end
    
  consumer = Thread.new do
    loop do
      @dblogger.log( @log.pop, 'out' )
    end
  end
                         
  consumer.join
    
rescue Errno::ENOENT => e
  # If the command doesn't exist, catch that as well, and log it as if it were
  # on stderr.
  @stderr << e.message
  @stderr << e.backtrace.join("\n")
  
  # Exit with the standard not found code.
  exit 127
end

# Exit with the process's exit code.
exit @status.exitstatus