# Prometheus Plugs [![Hex.pm](https://img.shields.io/hexpm/v/prometheus_plugs.svg?maxAge=2592000?style=plastic)](https://hex.pm/packages/prometheus_plugs)

Elixir Plug integration for [prometheus.erl](https://github.com/deadtrickster/prometheus.erl)

***TL;DR*** [Example app](https://github.com/deadtrickster/prometheus-plugs-example)

### Instrumentation

To instrument whole plug pipeline use `Prometheus.PlugPipelineInstrumenter`:

```elixir
defmodule MyApp.Endpoint.PipelineInstrumenter do
  use Prometheus.PlugPipelineInstrumenter
end
```

To instrument just a single plug use `Prometheus.PlugInstrumenter`:

```elixir
defmodule MyApp.CoolPlugInstrumenter do
  use Prometheus.PlugInstrumenter
end
```

Both modules implement plug interface and `Prometheus.PlugInstrumenter` generates proxy for specified plug so you'll need to replace instrumented plug with your instrumenter in pipeline.

Instrumenters configured via `:prometheus` app environment. Please consult respective modules documentation on
what options are available.

### Exporting

To export metric we first have to create a plug that will serve scraping requests.

```elixir
defmodule MyApp.MetricsExporter do
  use Prometheus.PlugExporter
```

Then we add exporter to MyApp pipeline:

```elixir
plug MyApp.MetricsExporter
```

You can configure path, export format and Prometheus registry via `:prometheus` app environment. For more information please see `Prometheus.PlugExporter` module documenataion.

## Documentation

Please find documentation on [hexdocs](https://hexdocs.pm/prometheus_plugs/index.html).

## Installation

The package can be installed as:

  1. Add prometheus_plug to your list of dependencies in `mix.exs`:

        def deps do
          [{:prometheus_plugs, "~> 0.7"}]
        end

  2. Ensure prometheus is started before your application:

        def application do
          [applications: [:prometheus]]
        end


## License

MIT