# `Rheo.Telemetry.Metrics`
[🔗](https://github.com/thanos/rheo/blob/v1.0.0/lib/rheo/telemetry/metrics.ex#L3)

Optional `Telemetry.Metrics` definitions for Rheo (v0.10+ / ADR 027).

Requires `{:telemetry_metrics, "~> 1.0"}` (or compatible) in the host app.
Wire into LiveDashboard, PromEx, or any reporter that accepts metric specs.

These are counters / summaries over existing `[:rheo, …]` events — they do
not change settle semantics. Alert thresholds stay in the host.

## Host wiring

Append `metrics/0` to your app's metric list (Phoenix Telemetry module,
PromEx plugin, or a custom reporter):

    defmodule MyAppWeb.Telemetry do
      use Supervisor
      import Telemetry.Metrics

      def start_link(arg) do
        Supervisor.start_link(__MODULE__, arg, name: __MODULE__)
      end

      @impl true
      def init(_arg) do
        children = [
          {:telemetry_poller, measurements: [], period: 10_000}
        ]

        Supervisor.init(children, strategy: :one_for_one)
      end

      def metrics do
        [
          # … host metrics …
        ] ++ Rheo.Telemetry.Metrics.metrics()
      end
    end

LiveDashboard (when the reporter uses that module):

    live_dashboard "/dashboard",
      metrics: MyAppWeb.Telemetry,
      additional_pages: [rheo: Rheo.LiveDashboard.Page]

See `Rheo.Telemetry` for the underlying event names.

# `metrics`

```elixir
@spec metrics() :: [Telemetry.Metrics.t()]
```

Canonical Rheo metric definitions for host reporters.

## Returns

A list of `Telemetry.Metrics` structs covering create / lease / dead-letter
counters and append / fetch / ack duration summaries.

## Examples

    iex> length(Rheo.Telemetry.Metrics.metrics()) > 0
    true

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