module MiGA::Common::WithDaemon

Helper module with specific functions to handle objects that have daemons. The class including it must +extend MiGA::Common::WithDaemonClass+ and define:

#daemon_home Path to the daemon's home
#daemon_name Name of the daemon
#daemon_loop One loop of the daemon to be repeatedly called
#daemon_first_loop To be executed before the first call to #daemon_loop

Attributes

declare_alive_pid[R]

Process ID of the forked process declaring the daemon alive

loop_i[R]

Loop counter

Public Instance Methods

active?() click to toggle source

Is the daemon active?

# File lib/miga/common/with_daemon.rb, line 46
def active?
  return false unless File.exist? alive_file

  (last_alive || Time.new(0)) > Time.now - 60
end

alive_file() click to toggle source

# File lib/miga/common/with_daemon.rb, line 30
def alive_file
  self.class.alive_file(daemon_home)
end

daemon(task, opts = [], wait = true) click to toggle source

Launches the task with options opts (as command-line arguments) and returns the process ID as an Integer. If wait it waits for the process to complete, immediately returns otherwise. Supported tasks: start, run, stop, status.

# File lib/miga/common/with_daemon.rb, line 127
def daemon(task, opts = [], wait = true)
  MiGA::MiGA.DEBUG "#{self.class}#daemon #{task} #{opts}"
  task = task.to_sym
  raise "Unsupported task: #{task}" unless respond_to? task
  return send(task, opts, wait) unless %[start run].include? task

  # start & run:
  options = default_options
  opts.unshift(task.to_s)
  options[:ARGV] = opts
  # This additional degree of separation below was introduced so the Daemons
  # package doesn't kill the parent process in workflows.
  pid = fork { launch_daemon_proc(options) }
  Process.wait(pid) if wait
  pid
end

declare_alive() click to toggle source

Tell the world that you're alive.

# File lib/miga/common/with_daemon.rb, line 54
def declare_alive
  if active?
    raise "Trying to declare alive an active daemon, if you think this is a"          " mistake please remove #{alive_file} or try again in 1 minute"
  end
  @declare_alive_pid = fork { declare_alive_loop }
  sleep(1) # <- to wait for the process check
end

declare_alive_loop(pid = Process.ppid) click to toggle source

Loop checking if the process with PID pid is still alive. By default, the parent process. Do not use directly, use declare_alive instead. Returns a symbol indicating the reason to stop:

:no_home Daemon's home does not exist
:no_process_alive Process is not currently running
:termination_file Found termination file

# File lib/miga/common/with_daemon.rb, line 71
def declare_alive_loop(pid = Process.ppid)
  i = -1
  loop do
    i += 1
    return :no_home unless Dir.exist? daemon_home
    return :no_process_alive unless process_alive? pid

    write_alive_file if i % 30 == 0
    return :termination_file if termination_file? pid

    sleep(1)
  end
end

default_options() click to toggle source

Returns Hash containing the default options for the daemon.

# File lib/miga/common/with_daemon.rb, line 115
def default_options
  {
    dir_mode: :normal, dir: daemon_home, multiple: false, log_output: true,
    stop_proc: :terminate
  }
end

in_loop() click to toggle source

One loop, returns a boolean indicating if the execution should continue

# File lib/miga/common/with_daemon.rb, line 187
def in_loop
  if loop_i.nil?
    declare_alive
    daemon_first_loop
    @loop_i = -1
  end
  @loop_i += 1
  daemon_loop
end

last_alive() click to toggle source

When was the daemon last seen active?

# File lib/miga/common/with_daemon.rb, line 40
def last_alive
  self.class.last_alive(daemon_home)
end

launch_daemon_proc(options) click to toggle source

Pass daemon options to Daemons. Do not use directly, use daemon instead.

# File lib/miga/common/with_daemon.rb, line 169
def launch_daemon_proc(options)
  Daemons.run_proc("#{daemon_name}", options) { while in_loop; end }
end

output_file() click to toggle source

# File lib/miga/common/with_daemon.rb, line 22
def output_file
  File.join(daemon_home, "#{daemon_name}.output")
end

pid_file() click to toggle source

# File lib/miga/common/with_daemon.rb, line 18
def pid_file
  File.join(daemon_home, "#{daemon_name}.pid")
end

process_alive?(pid) click to toggle source

Check if the process with PID pid is still alive, call terminate otherwise.

# File lib/miga/common/with_daemon.rb, line 92
def process_alive?(pid)
  Process.kill(0, pid)
  true
rescue Errno::ESRCH, Errno::EPERM, Errno::ENOENT
  terminate
  false
end

run(opts = [], wait = true) click to toggle source

Initializes the daemon on top with opts

# File lib/miga/common/with_daemon.rb, line 181
def run(opts = [], wait = true)
  daemon(:run, opts, wait)
end

start(opts = [], wait = true) click to toggle source

Initializes the daemon with opts

# File lib/miga/common/with_daemon.rb, line 175
def start(opts = [], wait = true)
  daemon(:start, opts, wait)
end

status(opts = [], wait = true) click to toggle source

Returns the status of the daemon with opts

# File lib/miga/common/with_daemon.rb, line 159
def status(opts = [], wait = true)
  if active?
    say "Running with pid #{File.size?(pid_file) ? File.read(pid_file) : '?'}"
  else
    say 'Not running'
  end
end

stop(opts = [], wait = true) click to toggle source

Stops the daemon with opts

# File lib/miga/common/with_daemon.rb, line 146
def stop(opts = [], wait = true)
  if active?
    say 'Sending termination message'
    FileUtils.touch(terminate_file)
    sleep(0.5) while active? if wait
    File.unlink(pid_file) if File.exist?(pid_file)
  else
    say 'No running instances'
  end
end

terminate() click to toggle source

Declares a daemon termination. Do not use, directly, use stop instead.

# File lib/miga/common/with_daemon.rb, line 199
def terminate
  unless declare_alive_pid.nil?
    Process.kill(9, declare_alive_pid)
    @declare_alive_pid = nil
  end
  File.rename(alive_file, terminated_file) if File.exist? alive_file
end

terminate_file() click to toggle source

# File lib/miga/common/with_daemon.rb, line 26
def terminate_file
  File.join(daemon_home, 'terminate-daemon')
end

terminated_file() click to toggle source

# File lib/miga/common/with_daemon.rb, line 34
def terminated_file
  self.class.terminated_file(daemon_home)
end

termination_file?(pid) click to toggle source

Check if a termination file exists and terminate process with PID pid if it does. Do not kill any process if pid is nil

# File lib/miga/common/with_daemon.rb, line 103
def termination_file?(pid)
  return false unless File.exist? terminate_file

  say 'Found termination file, terminating'
  File.unlink(terminate_file)
  terminate
  Process.kill(9, pid) unless pid.nil?
  true
end

write_alive_file() click to toggle source

# File lib/miga/common/with_daemon.rb, line 85
def write_alive_file
  File.open(alive_file, 'w') { |fh| fh.print Time.now.to_s }
end