# `KubernetesProbes.Drainer`
[🔗](https://gitlab.com/pandosearch/kubernetes_probes/blob/v0.1.0/lib/kubernetes_probes/drainer.ex#L1)

Holds the k8s readiness-probe status and enforces a drain window on shutdown.

On `SIGTERM`, OTP walks the supervision tree in reverse start order and
terminates children in reverse order. This `GenServer` **must be the last
child** of your application supervisor so it terminates first. Its
`terminate/2` flips the `/probe/readiness` probe to 503 via `:persistent_term`
and sleeps for the drain window, giving Kubernetes time to stop routing
traffic and allowing in-flight requests to finish before other resources
(Repo, Endpoint, etc.) are torn down.

## Usage

    # lib/my_app/application.ex — last entry in children
    children = [
      MyApp.Repo,
      MyAppWeb.Endpoint,
      {KubernetesProbes.Drainer, otp_app: :my_app}
    ]

## Configuration

    # config/config.exs — production default
    config :my_app, KubernetesProbes.Drainer, wait: 20_000

    # config/dev.exs — avoid 20s hang on Ctrl-C
    config :my_app, KubernetesProbes.Drainer, wait: 100

    # config/test.exs — avoid slow suite teardown
    config :my_app, KubernetesProbes.Drainer, wait: 10

## Options

  * `:otp_app` — the OTP application to read configuration from (required).
  * `:wait` — drain window in milliseconds. Can be set via config (see above)
    or passed directly to override config: `{KubernetesProbes.Drainer, otp_app: :my_app, wait: 5_000}`.
    Defaults to `20_000`.

# `child_spec`

Returns a specification to start this module under a supervisor.

See `Supervisor`.

# `start_link`

# `status`

```elixir
@spec status() :: :running | :stopping
```

---

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