csfrancis · July 28, 2016 18:49 · Jul 28, 2016
diff --git a/foo.rb b/foo.rb
@@ -0,0 +1,133 @@
+#!/usr/bin/env ruby
+
+NGINX_PID_FILE = "/var/run/nginx.pid"
+NGINX_OLD_PID_FILE = "/var/run/nginx.pid.oldbin"
+NGINX_CONF_FILE = "/etc/nginx/nginx.conf"
+NGINX_BIN = "/usr/sbin/nginx"
+LD_OVERRIDES = "/etc/nginx/ld-overrides"
+DEFAULT_NGINX_WORKERS = 2
+
+def with_term_color(color, eol: true)
+  @has_colors ||= `tput colors`.to_i > 0 ? true : false
+  $stdout.print "#{color}" if @has_colors
+  yield
+  $stdout.print "\e[0m" if @has_colors
+  $stdout.print "\n" if eol
+end
+
+def error(msg, should_exit: true)
+  with_term_color("\e[0;31m") { $stdout.print(msg) }
+  exit 1 if should_exit
+end
+
+def warning(msg)
+  with_term_color("\e[0;32m") { $stdout.print(msg) }
+end
+
+def with_timeout(seconds, timeout: 90, error_message: "error", warning_message: nil, exit_on_error: true)
+  count = 0
+  timeout.times do |i|
+    sleep 1
+    $stdout.print "."
+    count += 1
+    break if yield i
+  end
+
+  if count == timeout
+    if warning_message
+      warning(warning_message)
+    else
+      error(error_message, should_exit: exit_on_error)
+    end
+  else
+    $stdout.puts " done."
+  end
+end
+
+def get_child_processes(pid)
+  `pgrep -P #{pid}`.split.map{ |p| Integer(p) }
+end
+
+def get_process_cmdline(pids)
+  pids = [pids] unless pids.class == Array
+  pids.map do |pid|
+    begin
+      IO.read("/proc/#{pid}/cmdline").strip
+    rescue Errno::ENOENT
+      ""
+    end
+  end
+end
+
+def get_nginx_master_pid
+  Integer(IO.read(NGINX_PID_FILE).chomp)
+end
+
+def get_nginx_config_value(key)
+  match = File.read(NGINX_CONF_FILE).match(/#{key}\s+(\S+);/)
+  match.captures.first if match
+end
+
+def get_num_workers(pid)
+  get_process_cmdline(get_child_processes(pid)).count { |p| p.start_with? "nginx: worker process" }
+end
+
+def test_nginx_config
+  ld_library_path = ""
+  if Dir.exist? LD_OVERRIDES
+    ld_library_path = "LD_LIBRARY_PATH=#{LD_OVERRIDES} "
+  end
+
+  $stdout.print("Testing nginx configuration .. ")
+  unless system("#{ld_library_path}#{NGINX_BIN} -c #{NGINX_CONF_FILE} -t > /dev/null 2>&1")
+    error "nginx configuration is invalid!"
+  end
+  $stdout.puts("done.")
+end
+
+def spawn_new_nginx_master(master_pid)
+  $stdout.print "Spawning new nginx master .."
+  Process.kill("USR2", master_pid)
+  old_master_pid = master_pid
+  with_timeout 20, error_message: "timed out waiting for new master to spawn!" do
+    if File.exist?(NGINX_OLD_PID_FILE) && File.exist?(NGINX_PID_FILE)
+      new_pid = get_nginx_master_pid
+      error("error spawning new master - old master still running.") if new_pid == old_master_pid
+    end
+    # Check if the new master process has spawned with correct number of workers
+    expected_workers = Integer(get_nginx_config_value('worker_processes')) || DEFAULT_NGINX_WORKERS
+    get_num_workers(get_nginx_master_pid) == expected_workers
+  end
+end
+
+def shutdown_nginx_workers(old_master_pid)
+  $stdout.print "Shutting down workers on master .."
+  Process.kill("WINCH", old_master_pid)
+  with_timeout 90, warning_message: "not all workers shut down on time - killing stragglers." do
+    get_process_cmdline(get_child_processes(old_master_pid)).all? { |p| p.start_with? "nginx: master process" }
+  end
+
+  %w(TERM KILL).each do |sig|
+    sleep 0.1
+    workers = get_child_processes(old_master_pid).select { |p| get_process_cmdline(p)[0].start_with? "nginx: worker process" }
+    workers.each do |pid|
+      warning "Sending #{pid} #{sig}."
+      Process.kill(sig, pid) rescue Errno::ESRCH
+    end
+  end
+end
+
+def shutdown_old_nginx_master(master_pid)
+  $stdout.print "Waiting for old master to shut down .."
+  Process.kill("QUIT", master_pid)
+  with_timeout 10, error_message: "timed out waiting for old master to shut down!" do
+    ! File.exist? NGINX_OLD_PID_FILE
+  end
+end
+
+master_pid = get_nginx_master_pid
+test_nginx_config
+spawn_new_nginx_master(master_pid)
+shutdown_nginx_workers(master_pid)
+shutdown_old_nginx_master(master_pid)
+
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