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

Resolve the underlying backend issue identified by the wrapped error.

cache: failed to store raw key %q: %w

Error message

cache: failed to store raw key %q: %w

What it means

Thrown at middleware/cache/manager.go:188 by manager.setRaw() when storage.SetWithContext fails on the raw-bytes write path (used for cached bodies / ETag-stamped payloads). Same cause class as error 146 but for raw entries.

Source

Thrown at middleware/cache/manager.go:188

			return fmt.Errorf("cache: 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("cache: failed to store key %q: %w", m.logKey(key), err)
		}
		m.release(it)
		return nil
	}

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

// 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)

View on GitHub (pinned to 9a4c7e57fe)

Solutions

Resolve the underlying backend issue identified by the wrapped error.
Cap the size of cached bodies via the cache config / upstream response size to avoid hitting backend value-size limits.
Tune storage write timeout and pool to be resilient to brief outages.
Ensure the per-request context outlives the storage SET to avoid spurious ctx-cancellation errors.
Log and degrade gracefully via a custom ErrorHandler instead of returning 500 to the client.

Example fix

// before
store := redis.New()

// after: bound body size + explicit eviction policy
store := redis.New(redis.Config{
    URL: os.Getenv("REDIS_URL"),
})
app.Use(cache.New(cache.Config{
    Storage: store,
    MaxBytes: 1 << 20, // skip caching bodies > 1MB to avoid storage pressure
}))

Defensive patterns

Strategy: try-catch

Validate before calling

// Validate the backend accepts the largest raw value you intend to cache.
big := make([]byte, maxBodyBytes)
if err := store.SetWithContext(ctx, "__probe_big__", big, time.Second); err != nil {
    log.Fatalf("storage rejects raw payload size: %v", err)
}

Try / catch

if err := m.storage.SetWithContext(ctx, key, raw, exp); err != nil {
    log.Printf("raw cache write failed for %q: %v", key, err)
    return err
}

Prevention

Cap cached body size via the cache config / upstream to avoid storage value-size limits.
Probe write capability with a realistically-sized payload at startup.
Tune storage write timeout to fit the request lifetime.
Degrade to uncached serving on raw-write failure rather than 500-ing.

When it happens

Trigger: A raw cache write (body bytes) hits a failing Storage backend: out of memory, connection lost, ctx cancelled, or quota exceeded.

Common situations: Redis maxmemory-policy under load; disk full on persistent backends; ctx cancellation from client disconnect; transient network error to the storage host.

Related errors

AI-assisted analysis of gofiber/fiber@9a4c7e57fe (2026-08-04). Data as JSON: /data/errors/f70e1e0427619fe5.json. Report an issue: GitHub.