nginx-maxconn-module

nginx-maxconn-module provides directives to limit the number of simultaneous requests per user-defined key.

This module uses counter extension of yrmcds to count requests. External counting server enables us to count the requests consistently even if there are multiple nginx servers across multiple hosts.

Differences from limit_req

See #1.

Example configuration

server {
    # The address of yrmcds server to count requests.
    maxconn_server 127.0.0.1:11215;

    location / {
        # Limit requests up to 10 by their remote IP addresses.
        set $maxconn_key   $remote_addr;
        set $maxconn_limit 10;
        maxconn_acquire;

        # Specify the error page of 429 (Too Many Requests).
        error_page 429 /path/to/429.html;

        ...
    }

    location /foobar/ {
        # Limit requests by the pairs of the remote addrs and the request paths.
        set $maxconn_key   $remote_addr:$uri;
        set $maxconn_limit 6;
        maxconn_acquire;

        ...
    }
}

Directives

maxconn_server

Syntax: maxconn_server ADDR
Context: server

Specify the address of yrmcds server to count requests.

maxconn_acquire

Syntax: maxconn_acquire
Context: location

Send an Acquire command to increment the counter at yrmcds. If Acquire fails on Not acquired error, nginx returns "429 Too Many Client" to a client.

You need to define following variables before maxconn_acquire:

• $maxconn_key - the name of the counter to acquire.
• $maxconn_limit - the maximum value of the counter.

The incremented counter is automatically decremented at the end of the request.

maxconn_release

Syntax: maxconn_release
Context: location

Send a Release command to decrement the counter at yrmcds.

If Acquire command is not succeeded in the same request processing, this directive does nothing. Therefore, it is safe to execute maxconn_release without executing maxconn_acquire.

Install

Specify --add-module=/path/to/nginx-maxconn-module when you run ./configure.

Example:

./configure --add-module=/path/to/nginx-maxconn-module
make
make install

License

The BSD 2-Clause License.