What causes "limiter: failed to store key %q: %w" in gofiber/fiber?

Unwrap the error to find the storage-specific cause (e.g. OOM, LOCK_WAIT_TIMEOUT).

limiter: failed to store key

Error message

limiter: failed to store key %q: %w

What it means

The companion write error to error 180: storage.SetWithContext failed when persisting the updated hit count and expiry. The *item is released back to the pool on failure. The wrapped storage error is preserved for diagnosis.

Solutions

Unwrap the error to find the storage-specific cause (e.g. OOM, LOCK_WAIT_TIMEOUT).
For Redis: raise maxmemory or switch to an eviction policy that suits limiter semantics (allkeys-lru), and confirm maxclients is above your peak concurrency.
Confirm the storage connection pool size >= expected concurrent limiter writes.
Shorten limiter Expiration to reduce storage churn if keys accumulate.
If context cancellation is the cause, ensure the request lifetime exceeds storage write latency.

Example fix

// before: default redis with noeviction, writes fail under load
redis.NewRaw(redis.Config{URL: redisURL})

// after: sized maxmemory and eviction
redis.NewRaw(redis.Config{URL: redisURL}) // plus redis.conf: maxmemory 256mb, maxmemory-policy allkeys-lru

Defensive patterns

Strategy: retry

Validate before calling

// Pre-flight: confirm storage write capacity.
if err := store.Set("healthcheck", []byte("ok"), time.Minute); err != nil {
  return fmt.Errorf("storage not writable: %w", err)
}

Try / catch

// On write failure, degrade gracefully (e.g. fail-open with a log) if business permits.
if errors.Is(err, storage.ErrWrite) {
  log.Printf("limiter write failed, failing open: %v", err)
}

Prevention

Choose a Redis maxmemory policy that admits limiter writes (e.g. allkeys-lru, not noeviction).
Size maxclients and the connection pool above peak concurrency.
Keep limiter Expiration short enough that the working set fits in memory.
Monitor storage write-error rate as a leading indicator.

When it happens

Trigger: Redis OOM (maxmemory exceeded with noeviction), MySQL deadlocks or lock-wait timeout, storage disk full (SQLite), connection pool exhausted, context cancelled mid-write, ACL/permission denied on the storage namespace.

Common situations: Rate-limiter writes are write-heavy (one Set per request that hits the limiter); a Redis maxmemory policy of noeviction will start rejecting writes once the limit is hit; storage backend restarted mid-request; network partition between app and storage.

Related errors

AI-assisted analysis of gofiber/fiber@a105acad6c (2026-08-11). Data as JSON: /api/errors/182b8e4d161b9ad9. Report an issue: GitHub.

Appendix: source

Thrown at middleware/limiter/manager.go:106

	it, ok := value.(*item)
	if !ok {
		return nil, fmt.Errorf("limiter: unexpected entry type %T for key %q", value, m.logKey(key))
	}

	return it, nil
}

// set data to storage or memory
func (m *manager) set(ctx context.Context, key string, it *item, exp time.Duration) error {
	if m.storage != nil {
		raw, err := it.MarshalMsg(nil)
		if err != nil {
			m.release(it)
			return fmt.Errorf("limiter: failed to marshal key %q: %w", m.logKey(key), err)
		}
		if err := m.storage.SetWithContext(ctx, key, raw, exp); err != nil {
			m.release(it)
			return fmt.Errorf("limiter: failed to store key %q: %w", m.logKey(key), err)
		}
		m.release(it)
		return nil
	}

	m.memory.Set(key, it, exp)
	return nil
}

func (m *manager) logKey(key string) string {
	if m.shouldRedactKeys {
		return redactedKey
	}
	return key
}

View on GitHub (pinned to a105acad6c)