requestId()

Give every request a stable id so you can correlate log lines, across the request and across services.

Use case

When something goes wrong in production, you need to follow a single request through every log line it produced. A request id is that thread: attach it to each log, return it to the client, and a support ticket ("error, id abc123") points straight at the relevant logs.

How it works

It reuses an incoming X-Request-Id header if present (so an id set by your proxy or an upstream service carries through), otherwise it generates a UUID. It sets req.id for your handlers and echoes the id back in the X-Request-Id response header. Then it calls next(). There are no options.

Configuration

No options. Register it first, so every subsequent middleware, handler, and error can include req.id.

Example

Notes

Put requestId at (or near) the top of the chain, above errorHandler is fine since the id is set on req immediately, so the error log can reference it. Pass req.id into any downstream service call to extend the trace across process boundaries.

Next: timeout.