lib/process/daemon/controller.rb
# Copyright, 2014, by Samuel G. D. Williams. <http://www.codeotaku.com>
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
require 'rainbow'
module Process
class Daemon
# Daemon startup timeout
TIMEOUT = 5
# This module contains functionality related to starting and stopping the @daemon, and code for processing command line input.
class Controller
# `options[:output]` specifies where to write textual output describing what is going on.
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
# This function is called from the daemon executable. It processes ARGV and checks whether the user is asking for `start`, `stop`, `restart`, `status`.
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
# Fork a child process, detatch it and run the daemon code.
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.
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
def status
ProcessFile.status(@daemon)
end
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
# The pid of the daemon if it is available. The pid may be invalid if the daemon has crashed.
def pid
ProcessFile.recall(@daemon)
end
# How long to wait between checking the daemon process when shutting down:
STOP_PERIOD = 0.1
# The number of attempts to stop the daemon using SIGTERM. On the last attempt, SIGKILL is used.
STOP_ATTEMPTS = 5
# The factor which controls how long we sleep between attempts to kill the process. Only applies to processes which don't stop immediately.
STOP_WAIT_FACTOR = 3.0
# 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.
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
# Returns true if the process was stopped.
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
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
end
end
end