linux - How can a runit' service restart return instantly? -

i have runit service use run rails app using unicorn.

its restart command uses signal (usr2) handle zero-downtime restart. basically, waits until new process ready before old ones die.

this causes long (40 seconds) restart time, in service myservice restart doesn't return until end.

while can give runit longer timeout (which do), want make restart fire-and-forget kind of action it'll return instantly (or after usr2 signal fired, without waiting complete.

the entire logic taken multiple blog posts zero-downtime rails deployments unicorn restarts:

• https://gist.github.com/czarneckid/4639793
• https://gist.github.com/jeanmertz/8996796
• https://nulogy.com/who-we-are/company-blog/articles/zero-downtime-deployments-with-chef-nginx-and-unicorn/

this runit script (generated chef):

#!/bin/bash # # file managed chef, using <%= node.name %> cookbook. # editing file hand highly discouraged! #  exec 2>&1  # # since unicorn creates new pid on restart/reload, needs little # love manage runit. instead of managing unicorn directly, # trap signal calls service , redirect them unicorn directly. #   runit_pid=$$ application_name=<%= @options[:application_name] %> application_path=<%= file.join(@options[:path], 'current') %> bundle_cmd="<%= @options[:bundle_command] ? "#{@options[:bundle_command]} exec" : '' %>" unicorn_cmd=<%= @options[:unicorn_command] ? @options[:unicorn_command] : 'unicorn' %> unicorn_conf=<%= @options[:unicorn_config_path] ? @options[:unicorn_config_path] : file.join(@options[:path], 'current', 'config', 'unicorn.rb') %> rails_env=<%= @options[:rails_env] %> cur_pid_file=<%= @options['pid'] ? @options['pid'] : file.join(@options[:path], 'current', 'shared', 'pids', "#{@options[:application_name]}.pid") %> env_path=<%= @options[:env_dir] %> old_pid_file=$cur_pid_file.oldbin  echo "runit service restarted (pid: $runit_pid)"  function is_unicorn_alive {   set +e   if [ -n $1 ] && kill -0 $1 >/dev/null 2>&1;     echo "yes"   fi   set -e }  if [ -e $old_pid_file ];   old_pid=$(cat $old_pid_file)   echo "old master detected (pid: $old_pid), waiting quit"   while [ -n "$(is_unicorn_alive $old_pid)" ];     sleep 5   done fi  if [ -e $cur_pid_file ];   cur_pid=$(cat $cur_pid_file)   if [ -n "$(is_unicorn_alive $cur_pid)" ];     echo "detected running unicorn instance (pid: $cur_pid)"     running=true   fi fi  function start {   unset action   if [ $running ];     restart   else     echo 'starting new unicorn instance'     cd $application_path      exec chpst -e $env_path $bundle_cmd $unicorn_cmd -c $unicorn_conf -e $rails_env     sleep 3     cur_pid=$(cat $cur_pid_file)   fi }  function stop {   unset action   echo 'initializing graceful shutdown'   kill -quit $cur_pid    while [ -n "$(is_unicorn_alive $cur_pid)" ];     echo '.'     sleep 2   done    echo 'unicorn stopped, exiting runit process'   kill -9 $runit_pid }  function restart {   unset action   echo "restart request captured, swapping old master (pid: $cur_pid) new master usr2"   kill -usr2 $cur_pid    sleep 2   echo 'restarting runit service capture new master pid'   exit }  function alarm {   unset action   echo 'unicorn process interrupted' }  trap 'action=stop' stop term kill trap 'action=restart' quit usr2 int trap 'action=alarm' alrm  [ $running ] || action=start  if [ $action ];   echo "performing \"$action\" action , going sleep mode until new signal captured" elif [ $running ];   echo "going sleep mode until new signal captured" fi  if [ $action ] || [ $running ];   while true;     [ "$action" == 'start' ] && start     [ "$action" == 'stop' ] && stop     [ "$action" == 'restart' ] && restart     [ "$action" == 'alarm' ] && alarm     sleep 2   done fi 

this super weird way use runit, move reload logic control/h script , use sv hup (or since doesn't seem more sending usr2 sv 2). main run script shouldn't involved.