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