Log shutdown after sync

functions.php

add_action( 'transition_post_status' , 'log_after_sync_on_shutdown');

function log_after_sync_on_shutdown(){
  add_action( 'shutdown' , 'log_message_priority_11' , 11 );
}

function log_message_priority_11( ) {
  _log('Message post from shutdown priority 11.');
}