gofiber/fiber · error

failed to read response: %w

Error message

failed to read response: %w

What it means

Returned by maybeWriteCachedResponse (idempotency.go:71-72) when cfg.Storage.GetWithContext fails while trying to load a previously cached response for the idempotency key. This is a backend/storage failure, not a cache miss (a miss returns nil,nil).

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 9a4c7e57fe)

Solutions

1. Verify Storage connectivity and credentials at startup (ping/healthcheck).
2. Increase request timeout or storage operation timeout so GetWithContext doesn't race the context.
3. Use a more resilient Storage (cluster mode, retries inside the driver).
4. Consider a local in-memory Storage fallback so a remote outage degrades rather than fails.

Example fix

// before
app.Use(idempotency.New()) // in-memory only, fine, but...

// after — robust shared storage with healthcheck at boot
store := redis.New()
if err := store.Ping(); err != nil { log.Fatal(err) }
app.Use(idempotency.New(idempotency.Config{Storage: store}))

// startup connectivity check
store := redis.New()
ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
defer cancel()
if _, err := store.GetWithContext(ctx, "__hc__"); err != nil {
    log.Fatalf("storage unreachable: %v", err)
}

// fail open on transient read failures (idempotency is best-effort)
// wrap your handler so storage errors do not surface as 500

When it happens

Trigger: Configured Storage (Redis, MySQL, MongoDB, etc.) is unreachable, returns a network error, or the request context is cancelled/timed out before GetWithContext returns. Fires on the fast path before locking (line 119) and again after locking (line 135 — wrapped as [171]).

Common situations: Redis connection dropped; storage query exceeded the request deadline; misconfigured storage DSN; storage pod restarted mid-request; TLS handshake to storage failing intermittently.

Related errors

• cache: failed to get key %q from storage: %w
• cache: failed to get raw key %q from storage: %w
• cache: failed to store key %q: %w
• cache: failed to store raw key %q: %w
• failed to save response: %w

AI-assisted analysis of gofiber/fiber@9a4c7e57fe (2026-08-04). Data as JSON: /data/errors/1ce68bbd8ba6b10c.json. Report an issue: GitHub.