# `PromEx.Plugins.PlugCowboy`
[🔗](https://github.com/akoutmos/prom_ex/blob/master/lib/prom_ex/plugins/plug_cowboy.ex#L2)

This plugin captures HTTP request metrics emitted by Plug.Cowboy.

This plugin exposes the following metric group:
- `:plug_cowboy_http_event_metrics`

## Plugin options

- `routers`: **Required** This is a list with the full module names of your Routers (e.g MyAppWeb.Router).
  Phoenix and Plug routers are supported. When the Phoenix dependency is present in your project, a list of Phoenix Routers is expected. Otherwise a list of Plug.Router modules must be provided
- `event_prefix`: **Optional**, allows you to set the event prefix for the Telemetry events.
- `metric_prefix`: This option is OPTIONAL and is used to override the default metric prefix of
`[otp_app, :prom_ex, :plug_cowboy]`. If this changes you will also want to set `plug_cowboy_metric_prefix`
in your `dashboard_assigns` to the snakecase version of your prefix, the default
`plug_cowboy_metric_prefix` is `{otp_app}_prom_ex_plug_cowboy`.

- `duration_unit`: This is an OPTIONAL option and is a `Telemetry.Metrics.time_unit()`. It can be one of:
  `:second | :millisecond | :microsecond | :nanosecond`. It is `:millisecond` by default.

To use plugin in your application, add the following to your PromEx module:

```
defmodule WebApp.PromEx do
  use PromEx, otp_app: :web_app

  @impl true
  def plugins do
    [
      ...
      {PromEx.Plugins.PlugCowboy, routers: [MyApp.Router]}
    ]
  end

  @impl true
  def dashboards do
    [
      ...
      {:prom_ex, "plug_cowboy.json"}
    ]
  end
end
```

To ignore certain paths, pass a list of routes using the `:ignore_routes` option

```
defmodule WebApp.PromEx do
  use PromEx, otp_app: :web_app

  @impl true
  def plugins do
    [
      ...
      {PromEx.Plugins.PlugCowboy, routers: [MyApp.Router], ignore_routes: ["/metrics"]}
    ]
  end

  @impl true
  def dashboards do
    [
      ...
      {:prom_ex, "plug_cowboy.json"}
    ]
  end
end
```

---

*Consult [api-reference.md](api-reference.md) for complete listing*