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[BETA!] log-zmq: ZeroMQ logger module for NGINX

Installation

You can install this module in any RHEL-based distribution, including, but not limited to:

  • RedHat Enterprise Linux 7, 8, 9
  • CentOS 7, 8, 9
  • AlmaLinux 8, 9
  • Rocky Linux 8, 9
  • Amazon Linux 2 and Amazon Linux 2023
yum -y install https://extras.getpagespeed.com/release-latest.rpm
yum -y install nginx-module-log-zmq

Enable the module by adding the following at the top of /etc/nginx/nginx.conf:

load_module modules/ngx_http_log_zmq_module.so;

This document describes nginx-module-log-zmq v0 released on Nov 28 2021.

Production stability is not guaranteed.

ZeroMQ logger module for nginx.

ZeroMQ, \zero-em-queue\, is a protocol for messages exchange. It's a easy way to communicate using any language or platform via inproc, IPC, TCP, TPIC or multicast. It's asynchronous and only requires a small library.

Status

This module is already production ready.

Description

This is a nginx logger module integrated with ZeroMQ library.

nginx-log-zmq provides a very efficient way to log data for one or more PUB/SUB subscribers, over one or more different endpoints. This can be useful for data gathering and processing.

The message format can be the same as the tradicional log format which gives a interesting way to tail data via the network or exploring other text formats like JSON. As with the traditional log, it's possible to use nginx variables updated each request.

All messages are sent asynchronously and do not block the normal behaviour of the nginx server. As expected, the connections are resilient to network failures.

Synopsis

    http {
        # simple message to an IPC endpoint with 4 threads and 1000 queue elements

        log_zmq_server main "/tmp/main.ipc" ipc 4 1000;
        log_zmq_endpoint  main "/topic/";

        log_zmq_format main '{"remote_addr":"$remote_addr"}'

        # send messages to a subscriber listening at 127.0.0.1:5556

        log_zmq_server secondary 127.0.0.1:5556 tcp 4 1000;

        # set secondary endpoint
        log_zmq_endpoint secondary "/endpoint/";

        # set format using multiline
        log_zmq_format secondary '{"request_uri":"$request_uri",'
                                   '{"status":"$status"}';


        server {

            location /status {
                # mute all messages from log_zmq for this location

                log_zmq_off all;
            }

            location /endpoint {
                # mute main messages from log_zmq for this location

                log_zmq_off main;
            }
        }
    }

Directives

log_zmq_server

syntax: log_zmq_server <definition_name> <address> <ipc|tcp> <threads> <queue size>

default: no

context: http

Configures a server (PUB/SUB subscriber) to connect to.

The following options are required:

definition_name <name> - the name that nginx will use to identify this logger instance.

address <path>|<ipaddress>:<port> - the subscriber's address. If you are using the IPC protocol, you should specify the <path> for the unix socket. If you are using the TCP protocol, you should specify the <ipaddress> and <port> where your ZeroMQ subscriber is listening.

protocol <ipc|tcp> - the protocol to be used for communication.

threads <integer> - the number of I/O threads to be used.

queue_size <integer> - the maximum queue size for messages waiting to be sent.

log_zmq_endpoint

syntax: log_zmq_endpoint <definition_name> "<topic>"

default: no

context: http

Configures the topic for the ZeroMQ messages.

definition_name <name> - the name that nginx will use to identify this logger instance.

topic <topic> - the topic for the messages. This is a string (which can be a nginx variable) prepended to every sent message. For example, if you send the message "hello" to the "/talk:" topic, the message will end up as "/talk:hello".

Example:

http {
    log_zmq_server main "/tmp/example.ipc" 4 1000;

    # send a message for for an topic based on response status
    log_zmq_endpoint main "/remote/$status";
}

log_zmq_format

syntax: log_zmq_format <definition_name> "<format>"

default: no

context: http

Configures the ZeroMQ message format.

definition_name <name> - the name that nginx will use to identify this logger instance.

format <format> - the format for the messages. This defines the actual messages sent to the PUB/SUB subscriber. It follows the sames rules as the standard log_format directive. It is possible to use nginx variables here, and also to break it over multiple lines.

http {
    log_zmq_format main '{"line1": value,'
                          '{"line2": value}';
}

log_zmq_off

syntax: log_zmq_off <definition_name>|all

default: no

context: location

Turn off ZeroMQ logging in the current context.

definition_name <name> the name of the logger instance to be muted. If the special all name is used, all logger instances are muted.

GitHub

You may find additional configuration tips and documentation for this module in the GitHub repository for nginx-module-log-zmq.