Module ngx_stream_limit_conn_module

The ngx_stream_limit_conn_module module (1.9.3) is used to limit the number of connections per the defined key, in particular, the number of connections from a single IP address.

stream {
    limit_conn_zone $binary_remote_addr zone=addr:10m;

    ...

    server {

        ...

        limit_conn           addr 1;
        limit_conn_log_level error;
    }
}

Sets the shared memory zone and the maximum allowed number of connections for a given key value. When this limit is exceeded, the server will close the connection. For example, the directives

limit_conn_zone $binary_remote_addr zone=addr:10m;

server {
    ...
    limit_conn addr 1;
}

allow only one connection per an IP address at a time.

When several limit_conn directives are specified, any configured limit will apply.

These directives are inherited from the previous configuration level if and only if there are no limit_conn directives defined on the current level.

limit_conn_dry_run off;

Enables the dry run mode. In this mode, the number of connections is not limited, however, in the shared memory zone, the number of excessive connections is accounted as usual.

limit_conn_log_level error;

Sets the desired logging level for cases when the server limits the number of connections.

Sets parameters for a shared memory zone that will keep states for various keys. In particular, the state includes the current number of connections. The key can contain text, variables, and their combinations (1.11.2). Connections with an empty key value are not accounted. Usage example:

limit_conn_zone $binary_remote_addr zone=addr:10m;

Here, the key is a client IP address set by the $binary_remote_addr variable. The size of $binary_remote_addr is 4 bytes for IPv4 addresses or 16 bytes for IPv6 addresses. The stored state always occupies 32 or 64 bytes on 32-bit platforms and 64 bytes on 64-bit platforms. One megabyte zone can keep about 32 thousand 32-byte states or about 16 thousand 64-byte states. If the zone storage is exhausted, the server will close the connection.

$limit_conn_status

keeps the result of limiting the number of connections (1.17.6): PASSED, REJECTED, or REJECTED_DRY_RUN