nats-io/nats-server · error

config required

Error message

config required

What it means

Guard inside newMemStoreWithMode: the StreamConfig pointer passed to create a JetStream memory store is nil, so the store cannot determine retention, limits, or subject filters. Callers are newMemStore and setupStore, so this indicates a stream being created without a config.

Source

Thrown at server/memstore.go:64

	ageChk      *time.Timer // Timer to expire messages.
	ageChkRun   bool        // Whether message expiration is currently running.
	ageChkTime  int64       // When the message expiration is scheduled to run.
	recovering  bool        // Timers, schedules, TTLs etc won't fire while set.
	consumers   []ConsumerStore
	receivedAny bool
	ttls        *thw.HashWheel
	scheduling  *MsgScheduling
	sdm         *SDMMeta
	sources     map[string]*StreamSourceState
}

func newMemStore(cfg *StreamConfig) (*memStore, error) {
	return newMemStoreWithMode(cfg, false)
}

func newMemStoreWithMode(cfg *StreamConfig, recovering bool) (*memStore, error) {
	if cfg == nil {
		return nil, fmt.Errorf("config required")
	}
	if cfg.Storage != MemoryStorage {
		return nil, fmt.Errorf("memStore requires memory storage type in config")
	}
	ms := &memStore{
		msgs:       make(map[uint64]*StoreMsg),
		fss:        stree.NewSubjectTree[SimpleState](),
		maxp:       cfg.MaxMsgsPer,
		cfg:        *cfg,
		recovering: recovering,
	}
	// Only create a THW if we're going to allow TTLs.
	if cfg.AllowMsgTTL {
		ms.ttls = thw.NewHashWheel()
	}
	if cfg.AllowMsgSchedules {
		ms.scheduling = newMsgScheduling(ms.runMsgScheduling)
		ms.scheduling.paused = recovering

View on GitHub (pinned to 3a66a489d2)

Solutions

1. Ensure StreamConfig is fully populated before calling newMemStore/setupStore
2. Validate stream creation requests at the API layer so a nil config never reaches the store constructor

When it happens

Trigger: Thrown at server/memstore.go:64 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/254301aa7178f84a. Report an issue: GitHub.