Class: Process::Daemon::Controller

Inherits:
Object
  • Object
show all
Defined in:
lib/process/daemon/controller.rb

Overview

This module contains functionality related to starting and stopping the @daemon, and code for processing command line input.

Constant Summary collapse

STOP_PERIOD =

How long to wait between checking the daemon process when shutting down:

0.1
STOP_ATTEMPTS =

The number of attempts to stop the daemon using SIGTERM. On the last attempt, SIGKILL is used.

5
STOP_WAIT_FACTOR =

The factor which controls how long we sleep between attempts to kill the process. Only applies to processes which don’t stop immediately.

3.0

Instance Method Summary collapse

Constructor Details

#initialize(daemon, options = {}) ⇒ Controller

‘options` specifies where to write textual output describing what is going on.



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# File 'lib/process/daemon/controller.rb', line 31

def initialize(daemon, options = {})
  @daemon = daemon
  
  @output = options[:output] || $stdout
  
  # How long to wait until sending SIGTERM and eventually SIGKILL to the daemon process group when asking it to stop:
  @stop_timeout = options[:stop_timeout] || 10.0
end

Instance Method Details

#daemonize(argv = ARGV) ⇒ Object

This function is called from the daemon executable. It processes ARGV and checks whether the user is asking for ‘start`, `stop`, `restart`, `status`.



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# File 'lib/process/daemon/controller.rb', line 41

def daemonize(argv = ARGV)
  case (argv.shift || :default).to_sym
  when :start
    start
    show_status
  when :stop
    stop
    show_status
    ProcessFile.cleanup(@daemon)
  when :restart
    stop
    ProcessFile.cleanup(@daemon)
    start
    show_status
  when :status
    show_status
  else
    @output.puts Rainbow("Invalid command. Please specify start, restart, stop or status.").red
  end
end

#pid ⇒ Object

The pid of the daemon if it is available. The pid may be invalid if the daemon has crashed.



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# File 'lib/process/daemon/controller.rb', line 158

def pid
  ProcessFile.recall(@daemon)
end

#show_status ⇒ Object 



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# File 'lib/process/daemon/controller.rb', line 138

def show_status
  case self.status
  when :running
    @output.puts Rainbow("Daemon status: running pid=#{ProcessFile.recall(@daemon)}").green
  when :unknown
    if @daemon.crashed?
      @output.puts Rainbow("Daemon status: crashed").red

      @output.flush
      @output.puts Rainbow("Dumping daemon crash log:").red
      @daemon.tail_log(@output)
    else
      @output.puts Rainbow("Daemon status: unknown").red
    end
  when :stopped
    @output.puts Rainbow("Daemon status: stopped").blue
  end
end

#spawn ⇒ Object

Fork a child process, detatch it and run the daemon code.



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# File 'lib/process/daemon/controller.rb', line 63

def spawn
  @daemon.prefork
  @daemon.mark_log

  fork do
    Process.setsid
    exit if fork

    ProcessFile.store(@daemon, Process.pid)

    File.umask 0000
    Dir.chdir @daemon.working_directory

    $stdin.reopen '/dev/null'
    $stdout.reopen @daemon.log_file_path, 'a'
    $stdout.sync = true
  
    $stderr.reopen $stdout
    $stderr.sync = true

    begin
      @daemon.spawn
    rescue Exception => error
      $stderr.puts "=== Daemon Exception Backtrace @ #{Time.now.to_s} ==="
      $stderr.puts "#{error.class}: #{error.message}"
      $!.backtrace.each { |at| $stderr.puts at }
      $stderr.puts "=== Daemon Crashed ==="
      $stderr.flush
    ensure
      $stderr.puts "=== Daemon Stopping @ #{Time.now.to_s} ==="
      $stderr.flush
    end
  end
end

#start ⇒ Object

This function starts the daemon process in the background.



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# File 'lib/process/daemon/controller.rb', line 99

def start
  @output.puts Rainbow("Starting #{@daemon.name} daemon...").blue

  case self.status
  when :running
    @output.puts Rainbow("Daemon already running!").blue
    return
  when :stopped
    # We are good to go...
  else
    @output.puts Rainbow("Daemon in unknown state! Will clear previous state and continue.").red
    ProcessFile.clear(@daemon)
  end

  spawn

  sleep 0.1
  timer = TIMEOUT
  pid = ProcessFile.recall(@daemon)

  while pid == nil and timer > 0
    # Wait a moment for the forking to finish...
    @output.puts Rainbow("Waiting for daemon to start (#{timer}/#{TIMEOUT})").blue
    sleep 1

    # If the @daemon has crashed, it is never going to start...
    break if @daemon.crashed?

    pid = ProcessFile.recall(@daemon)

    timer -= 1
  end
end

#status ⇒ Object

Prints out the status of the daemon



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# File 'lib/process/daemon/controller.rb', line 134

def status
  ProcessFile.status(@daemon)
end

#stop ⇒ Object

Stops the daemon process. This function initially sends SIGINT. It waits STOP_PERIOD and checks if the daemon is still running. If it is, it sends SIGTERM, and then waits a bit longer. It tries STOP_ATTEMPTS times until it basically assumes the daemon is stuck and sends SIGKILL.



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# File 'lib/process/daemon/controller.rb', line 172

def stop
  @output.puts Rainbow("Stopping #{@daemon.name} daemon...").blue

  # Check if the pid file exists...
  unless File.file?(@daemon.process_file_path)
    @output.puts Rainbow("Pid file not found. Is the daemon running?").red
    return
  end

  pid = ProcessFile.recall(@daemon)

  # Check if the @daemon is already stopped...
  unless ProcessFile.running(@daemon)
    @output.puts Rainbow("Pid #{pid} is not running. Has daemon crashed?").red
    @daemon.tail_log($stderr)
    return
  end

  pgid = -Process.getpgid(pid)
  
  # Stop by interrupt sends a single interrupt and waits for the process to terminate:
  unless stop_by_interrupt(pgid)
    # If the process is still running, we try sending SIGTERM followed by SIGKILL:
    @output.puts Rainbow("** Daemon did not stop gracefully after #{@stop_timeout}s **").red
    
    stop_by_terminate_or_kill(pgid)
  end

  # If after doing our best the @daemon is still running (pretty odd)...
  if ProcessFile.running(@daemon)
    @output.puts Rainbow("Daemon appears to be still running!").red
    return
  else
    @output.puts Rainbow("Daemon has left the building.").green
  end

  # Otherwise the @daemon has been stopped.
  ProcessFile.clear(@daemon)
end