Nginx HTTP Server - Fourth Edition

Limit connections

The mechanism induced by this module is a little more complex than regular ones. It allows you to define the maximum amount of simultaneous connections to the server for a specific zone.

The first step is to define the zone using the limit_conn_zone directive:

• Directive syntax is limit_conn_zone $variable zone=name:size;
• $variable is the variable that will be used to differentiate one client from another, typically $binary_remote_addr, the IP address of the client in binary format (more efficient than ASCII)
• name is an arbitrary name given to the zone
• size is the maximum size you allocate to the table storing session states

The following example defines zones based on the client IP addresses:

limit_conn_zone $binary_remote_addr ...