Controlling nginx

nginx can be controlled with signals. The process ID of the master process is written to the file /usr/local/nginx/logs/nginx.pid by default. This name may be changed at configuration time, or in nginx.conf using the pid directive.

The master process supports the following signals:

• TERM, INT fast shutdown

• QUIT graceful shutdown

• HUP

  changing configuration, keeping up with a changed time zone (only for FreeBSD and Linux), starting new worker processes with a new configuration, graceful shutdown of old worker processes

• USR1 re-opening log files

• USR2 upgrading an executable file

• WINCH graceful shutdown of worker processes

Individual worker processes can be controlled with signals as well, though it is not required. The supported signals are:

• TERM, INT fast shutdown

• QUIT graceful shutdown

• USR1 re-opening log files

• WINCH

  abnormal termination for debugging (requires debug_points to be enabled)

Updating Configuration and Upgrading Nginx

Updating NGINX configuration is a very simple, lightweight, and reliable operation. It typically just means running the nginx –s reload command, which checks the configuration on disk and sends the master process a SIGHUP signal.

When the master process receives a SIGHUP, it does two things:

1. Reloads the configuration and forks a new set of worker processes. These new worker processes immediately begin accepting connections and processing traffic (using the new configuration settings).

2. Signals the old worker processes to gracefully exit. The worker processes stop accepting new connections. As soon as each current HTTP request completes, the worker process cleanly shuts down the connection (that is, there are no lingering keepalives). Once all connections are closed, the worker processes exit.

References

• http://nginx.org/en/docs/control.html