Suppose we have several identical nodes which are the application servers of some n-tier service. And suppose we use Apache ZooKeeper to keep all the config\'s of our distribute
Nginx has two methods of changing configuration:
HUP
signal to the master process results in "reload". Nginx starts a bunch of new workers and lets the old workers to shutdown gracefully, i.e. they finish existing requests. There is no interruption of service. This method of configuration change is very lightweight and quick, but has few limitations: you cannot change cache zones or re-compile Perl scripts.
USR2
signal, then WINCH
and then QUIT
to the master process result in "executable upgrade" and this sequence lets completely re-read whole configuration and even upgrade the Nginx executable. It reloads disk caches as well (which maybe time consuming). This method results in no interruption of service too.
Official documentation