nginx-metrics-graphite

This is a Lua plugin for the Nginx web server that automatically collects and submits several important Nginx metrics to Graphite suitable for visualisation with e.g. Grafana.

In constrast to commercial and proprietary solutions such as Luameter or NGINX Plus with it's ngx_http_status_module, this plugin is open source software while featuring more and additional metrics compared to those available via the open source ngx_http_stub_status_module.

This plugin takes inspiration from other Nginx metric libraries like nginx-lua-prometheus but differs fundamentally in the metrics submission handling by. In certain intervals it automatically pushes metrics to the configured Graphite (i.e. Carbon) host using pure Lua code instead of exposing them via a separate web page for polling.

The metrics collection happens on every request for which the user configures a suitable log_by_lua direcitve and towards server-wide global counters (finer granularity might be added later). The counters are realized using a single shared dictionary across all Nginx worker threads which has constant memory usage (128 KiB currently, may be reduced further).

Collected metrics in this prototype implementation:

• number of requests
• average request duration
• accumulated request sizes over all requests
• accumulated response sizes over all requests
• HTTP status code classes (1xx, 2xx, 3xx, 4xx, 5xx)
• HTTP methods (GET, HEAD, PUT, POST, DELETE, OPTIONS, others)

Caveats

A short metric submission interval might cause blocking on the Nginx worker threads since the shared dictionary storing all counters has to be locked.

Intermittent network errors while communicating with Graphite might leed to permanent loss of metric information.

Install

• Install nginx-extra (includes Lua support) on Debian Jessie

• Clone the nginx-metrics-graphite repository to /opt/nginx-metrics-graphite

• Add the following config to top-level http block:

  resolver x.y.z.w; # DNS resolver IP address needed
  
  lua_shared_dict metrics_graphite 128k;
  lua_package_path ";;/opt/nginx-metrics-graphite/?.lua";
  init_by_lua 'metrics_graphite = require("metrics_graphite").init("graphite.example.net", 300, "my.node.nginx_metrics.prefix")';
  init_worker_by_lua 'metrics_graphite:worker()';
  

• Instrument the http block or any server or location beneath it using log_by_lua 'metrics_graphite:log()';