Changing to BindJetStream

Signed-off-by: Matthias Hanel <mh@synadia.com>

js.go

@@ -147,6 +147,9 @@ type js struct {
 	stc  chan struct{}
 	dch  chan struct{}
 	rr   *rand.Rand
+
+	// Assumes underlying objects exist and prevents additional lookups
+	bound bool
 }
 
 type jsOpts struct {
@@ -166,8 +169,9 @@ const (
 	defaultAccountCheck = 20 * time.Second
 )
 
-// JetStream returns a JetStreamContext for messaging and stream management.
-func (nc *Conn) JetStream(opts ...JSOpt) (JetStreamContext, error) {
+// BindJetStream returns a JetStreamContext for messaging and stream management that will NOT create
+// underlying objects like stream or durable. It assumes they exist already.
+func (nc *Conn) jetStream(opts ...JSOpt) (*js, error) {
 	js := &js{
 		nc: nc,
 		opts: &jsOpts{
@@ -181,26 +185,42 @@ func (nc *Conn) JetStream(opts ...JSOpt) (JetStreamContext, error) {
 			return nil, err
 		}
 	}
+	return js, nil
+}
 
+// BindJetStream returns a JetStreamContext for messaging and stream management that will NOT create
+// underlying objects like stream or durable. It assumes they exist already.
+func (nc *Conn) BindJetStream(opts ...JSOpt) (JetStreamContext, error) {
+	js, err := nc.jetStream(opts...)
+	if err != nil {
+		return nil, err
+	}
+	js.bound = true
+	return js, nil
+}
+
+// JetStream returns a JetStreamContext for messaging and stream management.
+func (nc *Conn) JetStream(opts ...JSOpt) (JetStreamContext, error) {
+	js, err := nc.jetStream(opts...)
+	if err != nil {
+		return nil, err
+	}
 	// If we have check recently we can avoid another account lookup here.
 	// We want these to be lightweight and created at will.
-	// The account check is permanently disabled when the api prefix is set to anything but default
-	if js.opts.pre == defaultAPIPrefix {
-		nc.mu.Lock()
-		now := time.Now()
-		checkAccount := now.Sub(nc.jsLastCheck) > defaultAccountCheck
-		if checkAccount {
-			nc.jsLastCheck = now
-		}
-		nc.mu.Unlock()
+	nc.mu.Lock()
+	now := time.Now()
+	checkAccount := now.Sub(nc.jsLastCheck) > defaultAccountCheck
+	if checkAccount {
+		nc.jsLastCheck = now
+	}
+	nc.mu.Unlock()
 
-		if checkAccount {
-			if _, err := js.AccountInfo(); err != nil {
-				if err == ErrNoResponders {
-					err = ErrJetStreamNotEnabled
-				}
-				return nil, err
+	if checkAccount {
+		if _, err := js.AccountInfo(); err != nil {
+			if err == ErrNoResponders {
+				err = ErrJetStreamNotEnabled
 			}
+			return nil, err
 		}
 	}
 
@@ -1033,6 +1053,9 @@ func (js *js) subscribe(subj, queue string, cb MsgHandler, ch chan *Msg, isSync
 
 	// Find the stream mapped to the subject if not bound to a stream already.
 	if o.stream == _EMPTY_ {
+		if js.bound {
+			return nil, fmt.Errorf("nats: a bound JS requires a stream name")
+		}
 		stream, err = js.lookupStreamBySubject(subj)
 		if err != nil {
 			return nil, err
@@ -1044,17 +1067,17 @@ func (js *js) subscribe(subj, queue string, cb MsgHandler, ch chan *Msg, isSync
 	// With an explicit durable name, then can lookup
 	// the consumer to which it should be attaching to.
 	consumer = o.cfg.Durable
-	if consumer == _EMPTY_ && o.noDurCreate {
-		return nil, fmt.Errorf("nats: NoCreate requires a durable name")
-	} else if consumer != _EMPTY_ && !o.noDurCreate {
+	if consumer == _EMPTY_ && js.bound {
+		return nil, fmt.Errorf("nats: a bound JS requires a durable name")
+	} else if consumer != _EMPTY_ && !js.bound {
 		// Only create in case there is no consumer already.
 		info, err = js.ConsumerInfo(stream, consumer)
 		if err != nil && err.Error() != "nats: consumer not found" {
 			return nil, err
 		}
 	}
 
-	if o.noDurCreate {
+	if js.bound {
 		attached = true
 		deliver = subj
 	} else if info != nil {
@@ -1359,8 +1382,6 @@ type subOpts struct {
 	mack bool
 	// For creating or updating.
 	cfg *ConsumerConfig
-	// Assert consumer exists and do not create it
-	noDurCreate bool
 }
 
 // ManualAck disables auto ack functionality for async subscriptions.
@@ -1386,15 +1407,6 @@ func Durable(name string) SubOpt {
 	})
 }
 
-// NoDurableCreate instructs the API to not create a durable.
-// If no durable name was provided, an error will be raised.
-func NoDurableCreate() SubOpt {
-	return subOptFn(func(opts *subOpts) error {
-		opts.noDurCreate = true
-		return nil
-	})
-}
-
 // DeliverAll will configure a Consumer to receive all the
 // messages from a Stream.
 func DeliverAll() SubOpt {