nats-io/nats-server · error

bad service response type

Error message

bad service response type

What it means

ErrBadServiceType is returned when service latency tracking is being applied to a service whose response type is not Singleton. Latency tracking in nats-server only supports request-reply services with singleton responses; attaching it to a service export with a different response type (e.g. Stream/Chunked) is rejected.

Source

Thrown at server/errors.go:117

	// ErrAccountExists is returned when an account is attempted to be registered
	// but already exists.
	ErrAccountExists = errors.New("account exists")

	// ErrBadAccount represents a malformed or incorrect account.
	ErrBadAccount = errors.New("bad account")

	// ErrReservedAccount represents a reserved account that can not be created.
	ErrReservedAccount = errors.New("reserved account")

	// ErrMissingAccount is returned when an account does not exist.
	ErrMissingAccount = errors.New("account missing")

	// ErrMissingService is returned when an account does not have an exported service.
	ErrMissingService = errors.New("service missing")

	// ErrBadServiceType is returned when latency tracking is being applied to non-singleton response types.
	ErrBadServiceType = errors.New("bad service response type")

	// ErrBadSampling is returned when the sampling for latency tracking is not 1 >= sample <= 100.
	ErrBadSampling = errors.New("bad sampling percentage, should be 1-100")

	// ErrAccountValidation is returned when an account has failed validation.
	ErrAccountValidation = errors.New("account validation failed")

	// ErrAccountExpired is returned when an account has expired.
	ErrAccountExpired = errors.New("account expired")

	// ErrNoAccountResolver is returned when we attempt an update but do not have an account resolver.
	ErrNoAccountResolver = errors.New("account resolver missing")

	// ErrAccountResolverUpdateTooSoon is returned when we attempt an update too soon to last request.
	ErrAccountResolverUpdateTooSoon = errors.New("account resolver update too soon")

	// ErrAccountResolverSameClaims is returned when same claims have been fetched.
	ErrAccountResolverSameClaims = errors.New("account resolver no new claims")

View on GitHub (pinned to 3a66a489d2)

Solutions

1. Only enable latency tracking on services whose response type is Singleton
2. Change the service export to Singleton if request-reply latency tracking is desired
3. Remove the tracking call for non-singleton (streaming) services; latency sampling is unsupported for them
4. Guard the call by checking the export's response type before enabling tracking

Example fix

// before
acc.AddServiceImport(other, "stream.svc", "")
acc.TrackServiceExportWithSampling("stream.svc", "results", 50) // streaming respType
// after
acc.AddServiceImport(other, "req.svc", "") // Singleton response
err := acc.TrackServiceExportWithSampling("req.svc", "results", 50)

// confirm the export is Singleton before enabling latency tracking
if ea := acc.exports.services[svc]; ea == nil || ea.respType != Singleton {
	return fmt.Errorf("latency tracking requires Singleton response type for %q", svc)
}

func isSingletonService(acc *Account, svc string) bool {
	acc.mu.RLock(); defer acc.mu.RUnlock()
	if acc.exports == nil || acc.exports.services == nil { return false }
	ea := acc.exports.services[svc]
	return ea != nil && ea.respType == Singleton
}

if err := acc.TrackServiceExportWithSampling(svc, resp, 100); err != nil {
	if errors.Is(err, ErrBadServiceType) { /* skip tracking for streaming services */ }
}

When it happens

Trigger: Calling Account.TrackServiceExportWithSampling(service, respType, sampling) where the exported service's ea.respType is anything other than Singleton — e.g. a streaming response service — at server/accounts.go:1309.

Common situations: Developers enabling latency tracking on a service export that was configured for streaming/chunked responses; copy-pasting tracking setup between singleton and streaming services; upgrading code where a service changed response type but the tracking call was not updated.

Related errors

• service missing
• bad sampling percentage, should be 1-100
• account validation failed
• account expired
• account resolver missing

AI-assisted analysis of nats-io/nats-server@3a66a489d2 (2026-09-02). Data as JSON: /api/errors/4417419e30db3c58. Report an issue: GitHub.