Request ID Middleware

requestId() assigns a unique ID to each request, makes it available as req.id, and echoes it in the response header. If the incoming request already carries the header, that value is reused instead of generating a new one.

Coming from Express?

Works like express-request-id. Same passthrough behaviour for upstream-supplied IDs.

Basic usage

import { requestId } from "bunway";

app.use(requestId());

app.get("/info", (req, res) => {
  res.json({ requestId: (req as any).id });
});

Every response gets X-Request-Id: <uuid>.

Reusing an upstream ID

If the caller sends X-Request-Id, that value is reused:

// Incoming: X-Request-Id: my-trace-id
// req.id === "my-trace-id"
// Response: X-Request-Id: my-trace-id

Useful for distributed tracing — the ID propagates end-to-end without any extra code.

Custom header name

app.use(requestId({ header: "X-Trace-Id" }));

Custom generator

app.use(requestId({ generator: () => `req-${Date.now()}` }));

Suppress response header

app.use(requestId({ setHeader: false }));
// req.id is set, but no header is written to the response

Options reference

Option	Type	Default	Description
header	string	"X-Request-Id"	Header to read from the request and write to the response.
generator	() => string	crypto.randomUUID	Function that produces a new ID when none is present.
setHeader	boolean	true	Write the ID into the response header.

For type details see RequestIdOptions in the API Reference.