Health and Readiness Presets (`app`)

Purpose

Explicit opt-in registration of standard health and readiness HTTP endpoints. No implicit registration occurs during bootstrap — presets are side-effect free until the caller explicitly enables them.

API

err := application.EnableHealthReadinessPresets(app.HealthReadinessOptions{
    HealthPath: "/healthz",  // optional — defaults to /healthz
    ReadyPath:  "/readyz",   // optional — defaults to /readyz
    ReadyChecks: []app.ReadyCheck{
        func() error { return db.Ping() },
    },
})

Endpoint Behavior

`GET /healthz`

Returns 200 OK once presets are registered. Signals the service is alive.

`GET /readyz`

Returns 200 OK only when:

Bootstrap invariants pass (config and server wired).
All registered readiness checks return nil.

Returns 503 Service Unavailable when any invariant or check fails.

Readiness checks are evaluated synchronously and deterministically on each request.

Error Conditions

Condition	Error
`UseServer()` not called yet	`app.ErrServerNotReady`
Blank path	`app.ErrInvalidPresetOptions`
Health and ready paths are identical	`app.ErrInvalidPresetOptions`
Path conflicts with existing route	`app.ErrRouteConflict`

No partial registration occurs on error — all-or-nothing.

Non-Goals

No implicit preset registration inside UseServer().
No provider-specific dependency probes built in — readiness checks are caller-provided.

Health and Readiness Presets (app)