HTTP ops helpers

Small helpers in serenade-http for request correlation, probes, and drain. They stay framework-owned (Serenade Middleware / AsyncMiddleware), not a Tower stack.

Request id

use serenade_http::{AsyncHttpKernel, AsyncRequestIdMiddleware, Request, Response, request_id};

let mut kernel = AsyncHttpKernel::from_sync(|request: &mut Request| {
    let _id = request_id(request);
    Ok(Response::text(200, "ok"))
});
kernel.push_middleware(AsyncRequestIdMiddleware);

• Header: x-request-id (inbound propagate, outbound echo)
• Attribute: _serenade_request_id (String)
• Empty inbound values are ignored; a new id is generated

Sync kernels use RequestIdMiddleware the same way.

Health / readiness

use serenade_http::{HealthMiddleware, HttpKernel, Readiness, Request, Response};

let readiness = Readiness::new();
let mut kernel = HttpKernel::new(|_request: &mut Request| Ok(Response::text(200, "app")));
kernel.push_middleware(HealthMiddleware::new(readiness.clone()));

Path	Meaning	Response
/healthz	Liveness	200 + ok
/readyz	Readiness	200 + ready, or 503 + not ready

Flip readiness.mark_not_ready() before draining traffic so load balancers stop sending new work.

Async: AsyncHealthMiddleware.

Graceful shutdown recipe

1. readiness.mark_not_ready() (fail /readyz).
2. Stop the HTTP listener:
   • Actix: bind_server → server.handle().stop(true).await, then await the server
   • Axum: bind_server → ShutdownHandle::shutdown(), then await_bound
3. Run application Kernel::shutdown() (bundle teardown) after the listener is down.

The HTTP adapters do not call Kernel::shutdown themselves: that type lives in serenade-kernel and stays optional at the adapter edge.