discourse/lib/demon/base.rb

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2013-11-01 18:57:50 -04:00
module Demon; end
# intelligent fork based demonizer
class Demon::Base
def self.start(count)
@demons ||= {}
count.times do |i|
(@demons["#{prefix}_#{i}"] ||= new(i)).start
end
end
def self.stop
return unless @demons
@demons.values.each do |demon|
demon.stop
end
end
def initialize(index)
@index = index
@pid = nil
@parent_pid = Process.pid
@monitor = nil
end
def pid_file
"#{Rails.root}/tmp/pids/#{self.class.prefix}_#{@index}.pid"
end
def stop
if @monitor
@monitor.kill
@monitor.join
@monitor = nil
end
if @pid
Process.kill("HUP",@pid)
@pid = nil
end
end
def start
if existing = already_running?
# should not happen ... so kill violently
Process.kill("TERM",existing)
end
return if @pid
if @pid = fork
write_pid_file
monitor_child
return
end
monitor_parent
establish_app
after_fork
end
def already_running?
if File.exists? pid_file
pid = File.read(pid_file).to_i
if alive?(pid)
return pid
end
end
nil
end
private
def monitor_child
@monitor ||= Thread.new do
while true
sleep 5
unless alive?(@pid)
STDERR.puts "#{@pid} died, restarting the process"
@pid = nil
start
end
end
end
end
def write_pid_file
FileUtils.mkdir_p(Rails.root + "tmp/pids")
File.open(pid_file,'w') do |f|
f.write(@pid)
end
end
def delete_pid_file
File.delete(pid_file)
end
def monitor_parent
Thread.new do
while true
unless alive?(@parent_pid)
Process.kill "QUIT", Process.pid
end
sleep 1
end
end
end
def alive?(pid)
begin
Process.getpgid(pid)
true
rescue Errno::ESRCH
false
end
end
def establish_app
Discourse.after_fork
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Signal.trap("HUP") do
begin
delete_pid_file
ensure
exit
end
end
# keep stuff simple for now
$stdout.reopen("/dev/null", "w")
$stderr.reopen("/dev/null", "w")
end
def after_fork
end
end