What causes "cache: failed to delete key %q: %w" in gofiber/fiber?

Check the wrapped error for permission (ACL) vs connectivity vs cancellation causes.

cache: failed to delete key

Error message

cache: failed to delete key %q: %w

What it means

Returned by manager.del when the external Storage's DeleteWithContext fails. Deletion is invoked during cache invalidation/eviction and during cleanup paths; failure here leaves a stale or orphaned entry in the backend.

Solutions

Check the wrapped error for permission (ACL) vs connectivity vs cancellation causes.
Ensure the configured Storage credentials have DEL permission.
Rely on TTL/expiration to eventually purge entries if explicit delete fails; do not fail the user request over a cleanup delete.
Verify connection pool health if deletes fail under load.

Example fix

// before: surfacing delete failure from invalidation
if err := manager.del(ctx, key); err != nil {
    return err
}

// after: invalidation is best-effort; TTL is the safety net
if err := manager.del(ctx, key); err != nil {
    log.Warn("cache delete failed; entry will expire via TTL:", err)
}

Defensive patterns

Strategy: try-catch

Validate before calling

func storageDeletable(ctx context.Context, s fiber.Storage) error {
    if err := s.SetWithContext(ctx, "__dprobe__", []byte("x"), time.Second); err != nil {
        return err
    }
    return s.DeleteWithContext(ctx, "__dprobe__")
}

Try / catch

// Cache deletes are best-effort; TTL is the backstop.
if err := manager.del(ctx, key); err != nil {
    log.Warn("cache delete failed; entry will expire via TTL:", err)
}

Prevention

Grant the Storage credentials DEL permission.
Keep TTLs short enough that failed deletes self-heal.
Do not block request handling on cache invalidation.

When it happens

Trigger: Any path calling manager.del (cache invalidation, MaxBytes eviction cleanup, store-error cleanup) against a Storage backend whose DeleteWithContext errors: backend down, network error, permission/ACL denial on DEL, context cancellation.

Common situations: Redis ACL missing the DEL permission; backend transient outage during an eviction; client disconnect during invalidation; storage driver connection pool exhausted under churn.

Related errors

AI-assisted analysis of gofiber/fiber@a105acad6c (2026-08-11). Data as JSON: /api/errors/23f067e76f113559. Report an issue: GitHub.

Appendix: source

Thrown at middleware/cache/manager.go:201

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

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

// delete data from storage or memory
func (m *manager) del(ctx context.Context, key string) error {
	if m.storage != nil {
		if err := m.storage.DeleteWithContext(ctx, key); err != nil {
			return fmt.Errorf("cache: failed to delete key %q: %w", m.logKey(key), err)
		}
		return nil
	}

	m.memory.Delete(key)
	return nil
}

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

View on GitHub (pinned to a105acad6c)