This is a Lua plugin for the Nginx web server that automatically collects and submits several important Nginx metrics to [Graphite](https://graphiteapp.org/) suitable for visualisation with e.g. [Grafana](http://grafana.org/).
In constrast to commercial and proprietary solutions such as [Luameter](https://luameter.com/) or [NGINX Plus](https://www.nginx.com/products/) with it's [ngx_http_status_module](http://nginx.org/en/docs/http/ngx_http_status_module.html), 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](http://nginx.org/en/docs/http/ngx_http_stub_status_module.html). (Yea, [other web servers](https://redmine.lighttpd.net/projects/1/wiki/Docs_ModStatus) deliver more information by default...)
This plugin takes inspiration from other Nginx metric libraries like [nginx-lua-prometheus](https://github.com/knyar/nginx-lua-prometheus) but differs fundamentally in the metrics submission handling. In certain intervals it automatically pushes metrics to the configured instance(s) of [Carbon](https://github.com/graphite-project/carbon/) using pure Lua code instead of exposing them via a separate web page for HTTP polling. For that is uses the Graphite plaintext protocol over TCP establishing a new connection for every push.
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:
Intermittent network errors while communicating with Graphite might leed to permanent loss of metric information. The communication happens in clear text and thus needs a secure separate network or other means.
