Module ngx_stream_core_module

• Example Configuration
• Directives
• listen
• preread_buffer_size
• preread_timeout
• proxy_protocol_timeout
• resolver
• resolver_timeout
• server
• stream
• tcp_nodelay
• variables_hash_bucket_size
• variables_hash_max_size
• Embedded Variables

The ngx_stream_core_module module is available since version 1.9.0. This module is not built by default, it should be enabled with the --with-stream configuration parameter.

Example Configuration

worker_processes auto;

error_log /var/log/nginx/error.log info;

events {
    worker_connections  1024;
}

stream {
    upstream backend {
        hash $remote_addr consistent;

        server backend1.example.com:12345 weight=5;
        server 127.0.0.1:12345            max_fails=3 fail_timeout=30s;
        server unix:/tmp/backend3;
    }

    upstream dns {
       server 192.168.0.1:53535;
       server dns.example.com:53;
    }

    server {
        listen 12345;
        proxy_connect_timeout 1s;
        proxy_timeout 3s;
        proxy_pass backend;
    }

    server {
        listen 127.0.0.1:53 udp;
        proxy_responses 1;
        proxy_timeout 20s;
        proxy_pass dns;
    }

    server {
        listen [::1]:12345;
        proxy_pass unix:/tmp/stream.socket;
    }
}

Directives

Sets the address and port for the socket on which the server will accept connections. It is possible to specify just the port. The address can also be a hostname, for example:

listen 127.0.0.1:12345;
listen *:12345;
listen 12345;     # same as *:12345
listen localhost:12345;

IPv6 addresses are specified in square brackets:

listen [::1]:12345;
listen [::]:12345;

UNIX-domain sockets are specified with the “unix:” prefix:

listen unix:/var/run/nginx.sock;

The ssl parameter allows specifying that all connections accepted on this port should work in SSL mode.

The udp parameter configures a listening socket for working with datagrams (1.9.13).

The proxy_protocol parameter (1.11.4) allows specifying that all connections accepted on this port should use the PROXY protocol.

The listen directive can have several additional parameters specific to socket-related system calls.

backlog=number

sets the backlog parameter in the listen() call that limits the maximum length for the queue of pending connections (1.9.2). By default, backlog is set to -1 on FreeBSD, DragonFly BSD, and macOS, and to 511 on other platforms.

rcvbuf=size

sets the receive buffer size (the SO_RCVBUF option) for the listening socket (1.11.13).

sndbuf=size

sets the send buffer size (the SO_SNDBUF option) for the listening socket (1.11.13).

bind

this parameter instructs to make a separate bind() call for a given address:port pair. The fact is that if there are several listen directives with the same port but different addresses, and one of the listen directives listens on all addresses for the given port (*:port), nginx will bind() only to *:port. It should be noted that the getsockname() system call will be made in this case to determine the address that accepted the connection. If the ipv6only or so_keepalive parameters are used then for a given address:port pair a separate bind() call will always be made.

ipv6only=on|off

this parameter determines (via the IPV6_V6ONLY socket option) whether an IPv6 socket listening on a wildcard address [::] will accept only IPv6 connections or both IPv6 and IPv4 connections. This parameter is turned on by default. It can only be set once on start.

reuseport

this parameter (1.9.1) instructs to create an individual listening socket for each worker process (using the SO_REUSEPORT socket option), allowing a kernel to distribute incoming connections between worker processes. This currently works only on Linux 3.9+ and DragonFly BSD.

Inappropriate use of this option may have its security implications.

so_keepalive=on|off|[keepidle]:[keepintvl]:[keepcnt]

this parameter configures the “TCP keepalive” behavior for the listening socket. If this parameter is omitted then the operating system’s settings will be in effect for the socket. If it is set to the value “on”, the SO_KEEPALIVE option is turned on for the socket. If it is set to the value “off”, the SO_KEEPALIVE option is turned off for the socket. Some operating systems support setting of TCP keepalive parameters on a per-socket basis using the TCP_KEEPIDLE, TCP_KEEPINTVL, and TCP_KEEPCNT socket options. On such systems (currently, Linux 2.4+, NetBSD 5+, and FreeBSD 9.0-STABLE), they can be configured using the keepidle, keepintvl, and keepcnt parameters. One or two parameters may be omitted, in which case the system default setting for the corresponding socket option will be in effect. For example,

so_keepalive=30m::10

will set the idle timeout (TCP_KEEPIDLE) to 30 minutes, leave the probe interval (TCP_KEEPINTVL) at its system default, and set the probes count (TCP_KEEPCNT) to 10 probes.

Different servers must listen on different address:port pairs.

Specifies a size of the preread buffer.

Specifies a timeout of the preread phase.

Specifies a timeout for reading the PROXY protocol header to complete. If no entire header is transmitted within this time, the connection is closed.

Configures name servers used to resolve names of upstream servers into addresses, for example:

resolver 127.0.0.1 [::1]:5353;

An address can be specified as a domain name or IP address, and an optional port. If port is not specified, the port 53 is used. Name servers are queried in a round-robin fashion.

By default, nginx will look up both IPv4 and IPv6 addresses while resolving. If looking up of IPv6 addresses is not desired, the ipv6=off parameter can be specified.

By default, nginx caches answers using the TTL value of a response. The optional valid parameter allows overriding it:

resolver 127.0.0.1 [::1]:5353 valid=30s;

Before version 1.11.3, this directive was available as part of our commercial subscription.

Sets a timeout for name resolution, for example:

resolver_timeout 5s;

Before version 1.11.3, this directive was available as part of our commercial subscription.

Sets the configuration for a server.

Provides the configuration file context in which the stream server directives are specified.

Enables or disables the use of the TCP_NODELAY option. The option is enabled for both client and proxied server connections.

Sets the bucket size for the variables hash table. The details of setting up hash tables are provided in a separate document.

Sets the maximum size of the variables hash table. The details of setting up hash tables are provided in a separate document.

Embedded Variables

The ngx_stream_core_module module supports variables since 1.11.2.

$binary_remote_addr

client address in a binary form, value’s length is always 4 bytes for IPv4 addresses or 16 bytes for IPv6 addresses

$bytes_received

number of bytes received from a client (1.11.4)

$bytes_sent

number of bytes sent to a client

$connection

connection serial number

$hostname

host name

$msec

current time in seconds with the milliseconds resolution

$nginx_version

nginx version

$pid

PID of the worker process

$protocol

protocol used to communicate with the client: TCP or UDP (1.11.4)

$proxy_protocol_addr

client address from the PROXY protocol header, or an empty string otherwise (1.11.4)

The PROXY protocol must be previously enabled by setting the proxy_protocol parameter in the listen directive.

$proxy_protocol_port

client port from the PROXY protocol header, or an empty string otherwise (1.11.4)

The PROXY protocol must be previously enabled by setting the proxy_protocol parameter in the listen directive.

$remote_addr

client address

$remote_port

client port

$server_addr

an address of the server which accepted a connection

Computing a value of this variable usually requires one system call. To avoid a system call, the listen directives must specify addresses and use the bind parameter.

$server_port

port of the server which accepted a connection

$session_time

session duration in seconds with a milliseconds resolution (1.11.4);

$status

session status (1.11.4), can be one of the following:

200

session completed successfully

400

client data could not be parsed, for example, the PROXY protocol header

403

access forbidden, for example, when access is limited for certain client addresses

500

internal server error

502

bad gateway, for example, if an upstream server could not be selected or reached.

503

service unavailable, for example, when access is limited by the number of connections

$time_iso8601

local time in the ISO 8601 standard format

$time_local

local time in the Common Log Format