How to debug a failing request — Intermediate

Misc / Other API testing & debugging

Trace the path: client → middleware → router → controller → service → database; read logs and status codes at each step.

Learn: When a request fails, resist random changes—follow the pipeline. Confirm the server port, route match, validation, service/SQL, then global error handler. Logs with request IDs from pino make this faster.

Supplementary examples

Temporary route-level log

router.post("/", (req, res, next) => {
  console.log("POST /users body", req.body);
  return controller.create(req, res, next);
});

Course example

// Typical order to inspect:
// 1. Server running? Correct PORT in .env?
// 2. Request URL and HTTP method match a route?
// 3. Validation middleware rejecting body? (400)
// 4. Service/SQL error? (500 + logs)
// 5. notFound if no route matched (404)

req.log.info({ params: req.params, body: req.body }, "debug");

Additional references & examples

Express.js guide
Routing, middleware order, and request/response lifecycle.
JSON formatter (online)
Pretty-print API responses when debugging (used in logging lessons).