gofiber/fiber · error

failed to save response

Error message

failed to save response: %w

What it means

Returned when cfg.Storage.SetWithContext fails while persisting the freshly computed response under the idempotency key for cfg.Lifetime. The wrapped %w is the storage backend's error. The handler executed, but the response could not be cached, so subsequent retries with the same key will re-execute the handler (no idempotency guarantee until a later write succeeds).

Solutions

1. Check storage health, capacity, and connectivity.
2. If the response is large, raise backend limits or exclude big payloads from caching via Next.
3. Decide whether to surface the failure to the client (current behavior) or log-and-continue.
4. Monitor SetWithContext error rate to detect capacity/availability issues.

When it happens

Trigger: After the request handler completes and the response is marshaled, Storage.SetWithContext(key, bs, Lifetime) returns a non-nil error — Redis/DB write failure, connection broken, value too large for the backend, or context cancellation.

Common situations: Storage backend full (Redis maxmemory eviction disabled), network partition during write, marshaled payload exceeds backend size limits, client disconnect cancelling the request context, or storage credentials revoked mid-flight.

Related errors

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

AI-assisted analysis of gofiber/fiber@a105acad6c (2026-08-11). Data as JSON: /api/errors/cfcc13b6c9f52b3d. Report an issue: GitHub.

Appendix: source

Thrown at middleware/idempotency/idempotency.go:180

				// Filter
				res.Headers = make(map[string][]string)
				for h, vals := range headers {
					if shouldKeepHeader(h) {
						res.Headers[h] = vals
					}
				}
			}
		}

		// Marshal response
		bs, err := res.MarshalMsg(nil)
		if err != nil {
			return fmt.Errorf("failed to marshal response: %w", err)
		}

		// Store response
		if err := cfg.Storage.SetWithContext(c, key, bs, cfg.Lifetime); err != nil {
			return fmt.Errorf("failed to save response: %w", err)
		}

		_ = c.Locals(localsKeyWasPutToCache, true)

		return nil
	}
}

View on GitHub (pinned to a105acad6c)