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#!/usr/bin/ruby |
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# restart-unicorn: Graceful restart for Unicorn |
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# depends on Linux's proc(5) |
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require 'scanf' |
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require 'timeout' |
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class ProcFS |
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PROC_DIR = '/proc' |
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# cf. proc(5) |
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PROC_STAT_FORMAT = [ |
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%w[pid %d], |
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%w[comm %s], |
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%w[state %c], |
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%w[ppid %d], |
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%w[pgrp %d], |
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%w[session %d], |
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] |
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STAT_PARAMS = PROC_STAT_FORMAT.map(&:first) |
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STAT_FORMAT = PROC_STAT_FORMAT.map(&:last).join(' ') |
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Stat = Struct.new(*STAT_PARAMS.map(&:to_sym)) |
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attr_reader :pid |
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STAT_PARAMS.each do |name| |
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next if method_defined?(name) |
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define_method(name) { stat && stat.send(name) } |
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end |
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def self.all |
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Dir.entries(PROC_DIR).grep(/\A\d+\z/).map {|pid| ProcFS.new(pid)} |
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end |
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def self.detect(options = {}, &block) |
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if timeout = options[:timeout] |
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Timeout.timeout(timeout) do |
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all.detect(&block) or (sleep 0.2 and redo) |
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end |
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else |
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all.detect(&block) |
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end |
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end |
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def initialize(pid) |
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@pid = pid.to_i |
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end |
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def stat |
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@stat ||= Stat.new(*read('stat').scanf(STAT_FORMAT)) |
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rescue |
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nil |
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end |
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def cmdline |
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@cmdline ||= read('cmdline').gsub(/\0/, ' ').strip |
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rescue |
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nil |
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end |
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private |
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def read(name) |
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File.read(File.join(PROC_DIR, @pid.to_s, name)) |
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end |
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end |
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if ARGV.size != 1 |
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puts "USAGE: #{File.basename($0)} PIDFILE" |
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exit |
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end |
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pid_file = ARGV.shift |
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shutdown_old_master_process = proc do |
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old_pid_file = pid_file + '.oldbin' |
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if File.exist?(old_pid_file) |
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Process.kill(:QUIT, File.read(old_pid_file).to_i) |
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File.unlink(old_pid_file) |
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end |
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end |
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# shutdown an old master process. (if exists) |
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shutdown_old_master_process.call |
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# find a current master process. |
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pid = File.read(pid_file).to_i |
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master_proccess = ProcFS.new(pid) |
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unless master_proccess.stat |
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STDERR.puts "Master process #{pid} is missing" |
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exit 1 |
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end |
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# send SIGUSR2 to the master. |
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Process.kill(:USR2, pid) |
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begin |
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# find a new master. |
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new_master_process = ProcFS.detect(:timeout => 5) do |process| |
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process.ppid == pid && process.cmdline =~ /\Aunicorn(?:_rails)? master/ |
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end |
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rescue Exception |
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# can't find a new master process. |
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STDERR.puts "#{$!.class}: #{$!.to_s}" |
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STDERR.puts "Can't find a new master process" |
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exit 1 |
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end |
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begin |
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# find a new worker process. |
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new_worker_process = ProcFS.detect(:timeout => 5) do |process| |
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process.ppid == new_master_process.pid && process.cmdline =~ /\Aunicorn(?:_rails)? worker/ |
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end |
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# wait for the worker to sleep. |
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timeout(60) do |
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count = 2 |
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begin |
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sleep 0.2 |
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stat = ProcFS.new(new_worker_process.pid).stat or raise "New worker process #{new_worker_process.pid} was died" |
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end until stat.state == 'S' && (count -= 1).zero? |
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end |
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# everything is ok. kill the old master process. |
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shutdown_old_master_process.call |
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rescue Exception |
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# something was failed. kill the new master process. |
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STDERR.puts "#{$!.class}: #{$!.to_s}" |
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STDERR.puts "Kill the new master process #{new_master_process.pid}" |
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Process.kill(:QUIT, new_master_process.pid) |
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exit 1 |
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end |
macks revised this gist