gofiber/fiber · error

failed to read response

Error message

failed to read response: %w

What it means

Returned by idempotency.maybeWriteCachedResponse when cfg.Storage.GetWithContext fails while looking up a cached response by key. The wrapped %w is the storage backend's error (Redis, MySQL, MongoDB, etc.). The fastpath or locked-path lookup aborts and the error bubbles up through the handler.

Solutions

1. Check storage connectivity and credentials (Redis ping, DB ping).
2. Ensure the Storage instance is properly configured (pool size, timeouts, TLS).
3. Decide on a failure policy: fail the request (current behavior) or fall back to memory storage with the caveat that idempotency is per-process.
4. Add health checks/alerts on the storage backend.

When it happens

Trigger: A non-safe request carries a valid X-Idempotency-Key and the configured Storage.GetWithContext returns a non-nil error — Redis connection lost, DB query timeout, malformed connection string, or context cancellation. Fires both on the pre-lock fastpath and post-lock re-check.

Common situations: Shared/distributed storage (Redis, MySQL) outage or network partition, storage credentials rotated but app not restarted, storage TTL/connection pool exhausted, or the request context cancelled by client disconnect mid-lookup.

Related errors

• cache: failed to delete key
• cache: failed to reload key
• cache: failed to restore heap index for key
• failed to save response
• failed to lock

AI-assisted analysis of gofiber/fiber@a105acad6c (2026-08-11). Data as JSON: /api/errors/1ce68bbd8ba6b10c. Report an issue: GitHub.

Appendix: source

Thrown at middleware/idempotency/idempotency.go:72

		}
		return key
	}

	// Snapshot the configured names so later mutation of the caller's slice
	// cannot change an already-constructed handler. Matching uses
	// utils.EqualFold, so no lowercased copies are needed and comparing
	// against the canonical-case names fasthttp reports stays allocation-free.
	keepResponseHeaders := slices.Clone(cfg.KeepResponseHeaders)

	shouldKeepHeader := func(header string) bool {
		return slices.ContainsFunc(keepResponseHeaders, func(keep string) bool {
			return utils.EqualFold(header, keep)
		})
	}

	maybeWriteCachedResponse := func(c fiber.Ctx, key string) (bool, error) {
		if val, err := cfg.Storage.GetWithContext(c, key); err != nil {
			return false, fmt.Errorf("failed to read response: %w", err)
		} else if val != nil {
			var res response
			if _, err := res.UnmarshalMsg(val); err != nil {
				return false, fmt.Errorf("failed to unmarshal response: %w", err)
			}

			_ = c.Status(res.StatusCode)

			for header, vals := range res.Headers {
				for _, val := range vals {
					c.RequestCtx().Response.Header.Add(header, val)
				}
			}

			if len(res.Body) != 0 {
				if err := c.Send(res.Body); err != nil {
					return true, err
				}

View on GitHub (pinned to a105acad6c)