nats-io/nats-server · error

memstore is nil

Error message

memstore is nil

What it means

Nil-receiver guard in memStore.ConsumerStore: the method was invoked on a nil *memStore, meaning the stream store was never created or has been torn down before a consumer was attached to it.

Source

Thrown at server/memstore.go:2594

func (ms *memStore) isClosed() bool {
	ms.mu.RLock()
	defer ms.mu.RUnlock()
	return ms.msgs == nil
}

type consumerMemStore struct {
	mu     sync.Mutex
	ms     StreamStore
	name   string
	cfg    ConsumerConfig
	state  ConsumerState
	closed bool
}

func (ms *memStore) ConsumerStore(name string, _ time.Time, cfg *ConsumerConfig) (ConsumerStore, error) {
	if ms == nil {
		return nil, fmt.Errorf("memstore is nil")
	}
	if ms.isClosed() {
		return nil, ErrStoreClosed
	}
	if cfg == nil || name == _EMPTY_ {
		return nil, fmt.Errorf("bad consumer config")
	}
	o := &consumerMemStore{ms: ms, name: name, cfg: *cfg}
	ms.AddConsumer(o)
	return o, nil
}

func (ms *memStore) AddConsumer(o ConsumerStore) error {
	ms.mu.Lock()
	ms.consumers = append(ms.consumers, o)
	ms.mu.Unlock()
	return nil
}

View on GitHub (pinned to 3a66a489d2)

Solutions

1. Check that the stream store was successfully created before adding consumers
2. Tear down consumers before closing/deleting the stream store

When it happens

Trigger: Thrown at server/memstore.go:2594 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of nats-io/nats-server@3a66a489d2 (2026-09-02). Data as JSON: /api/errors/d804bbfe9b2790fd. Report an issue: GitHub.