class Process::Daemon::Controller
This module contains functionality related to starting and stopping the @daemon, and code for processing command line input.
Constants
- STOP_ATTEMPTS
The number of attempts to stop the daemon using SIGTERM. On the last attempt, SIGKILL is used.
- STOP_PERIOD
How long to wait between checking the daemon process when shutting down:
- 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.
Public Class Methods
‘options` specifies where to write textual output describing what is going on.
# 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
Public Instance Methods
This function is called from the daemon executable. It processes ARGV and checks whether the user is asking for ‘start`, `stop`, `restart`, `status`.
# 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
The pid of the daemon if it is available. The pid may be invalid if the daemon has crashed.
# File lib/process/daemon/controller.rb, line 158 def pid ProcessFile.recall(@daemon) end
# 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
Fork a child process, detatch it and run the daemon code.
# 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} ===" $stderr.flush end end end
This function starts the daemon process in the background.
# File lib/process/daemon/controller.rb, line 99 def start @output.puts Rainbow("Starting #{@daemon.name} daemon...").blue case self.status when :running @output.puts Rainbow("Daemon already running!").blue return when :stopped # We are good to go... else @output.puts Rainbow("Daemon in unknown state! Will clear previous state and continue.").red ProcessFile.clear(@daemon) end spawn sleep 0.1 timer = TIMEOUT pid = ProcessFile.recall(@daemon) while pid == nil and timer > 0 # Wait a moment for the forking to finish... @output.puts Rainbow("Waiting for daemon to start (#{timer}/#{TIMEOUT})").blue sleep 1 # If the @daemon has crashed, it is never going to start... break if @daemon.crashed? pid = ProcessFile.recall(@daemon) timer -= 1 end end
Prints out the status of the daemon
# File lib/process/daemon/controller.rb, line 134 def status ProcessFile.status(@daemon) end
Stops the daemon process. This function initially sends SIGINT. It waits STOP_PERIOD
and checks if the daemon is still running. If it is, it sends SIGTERM, and then waits a bit longer. It tries STOP_ATTEMPTS
times until it basically assumes the daemon is stuck and sends SIGKILL.
# File lib/process/daemon/controller.rb, line 172 def stop @output.puts Rainbow("Stopping #{@daemon.name} daemon...").blue # Check if the pid file exists... unless File.file?(@daemon.process_file_path) @output.puts Rainbow("Pid file not found. Is the daemon running?").red return end pid = ProcessFile.recall(@daemon) # Check if the @daemon is already stopped... unless ProcessFile.running(@daemon) @output.puts Rainbow("Pid #{pid} is not running. Has daemon crashed?").red @daemon.tail_log($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
Private Instance Methods
Returns true if the process was stopped.
# File lib/process/daemon/controller.rb, line 215 def stop_by_interrupt(pgid) running = true # Interrupt the process group: Process.kill("INT", pgid) (@stop_timeout / STOP_PERIOD).ceil.times do if running = ProcessFile.running(@daemon) sleep STOP_PERIOD end end return !running end
# File lib/process/daemon/controller.rb, line 230 def stop_by_terminate_or_kill(pgid) # TERM/KILL loop - if the daemon didn't die easily, shoot it a few more times. (STOP_ATTEMPTS+1).times do |attempt| break unless ProcessFile.running(@daemon) # SIGKILL gets sent on the last attempt. signal_name = (attempt < STOP_ATTEMPTS) ? "TERM" : "KILL" @output.puts Rainbow("Sending #{signal_name} to process group #{pgid}...").red Process.kill(signal_name, pgid) # We iterate quickly to start with, and slow down if the process seems unresponsive. timeout = STOP_PERIOD + (attempt.to_f / STOP_ATTEMPTS) * STOP_WAIT_FACTOR @output.puts Rainbow("Waiting for #{timeout.round(1)}s for daemon to terminate...").blue sleep(timeout) end end