Nginx Module Reference manual: HTTP Limit Zone module (http Limit Zone)

These modules are all compiled into Nginx by default unless a module is manually specified to be excluded in configure.

This module can limit the number of simultaneous connections for a session specified by an address or some special circumstances.
The following example:

Instructions

Limit_zone

Syntax: Limit_zone zone_http://www.aliyun.com/zixun/aggregation/11696.html ">name $variable memory_max_size
Default value: No
Working with Fields: HTTP
The instruction describes the session-state storage area.
The number of sessions is determined by the variable you specify, depending on the variable size and memory_max_size value used.
The following example:

The client's address will be used for the session, noting that the $BINARY_REMOTE_ADDR variable will be used to replace $REMOTE_ADDR.
The value of the $remote _addr variable can be 7 to 15 bytes long, so the size is specified as 32 or 64 bytes.
The value of the $binary _remote_addr variable is always 4 bytes long and is always 32 bytes in size.
32,000 sessions can theoretically be processed when the session-state storage area is 1M, with each session size of 32 bytes.

Limit_conn

Syntax: Limit_conn zone_name max_clients_per_ip
Default value: No
Working with fields: HTTP, server, location
instruction specifies the maximum number of simultaneous connections for a session, and requests exceeding this number are returned to the Service unavailable (503) code.
The following example:

This specifies that an address can only have one connection at a time.

Limit_conn_log_level

Syntax: Limit_conn_log_level Info | Notice | Warn | Error
Default value: Error
Working with fields: HTTP, server, location
Log level is recorded when the maximum number of connections is reached.