fix(consumer): remove old nsqd connections if addresses change

consumer.go

@@ -33,9 +33,9 @@ type Handler interface {
 // HandlerFunc is a convenience type to avoid having to declare a struct
 // to implement the Handler interface, it can be used like this:
 //
-// 	consumer.AddHandler(nsq.HandlerFunc(func(m *Message) error {
-// 		// handle the message
-// 	}))
+//	consumer.AddHandler(nsq.HandlerFunc(func(m *Message) error {
+//		// handle the message
+//	}))
 type HandlerFunc func(message *Message) error
 
 // HandleMessage implements the Handler interface
@@ -220,8 +220,7 @@ func (r *Consumer) conns() []*Conn {
 // The logger parameter is an interface that requires the following
 // method to be implemented (such as the the stdlib log.Logger):
 //
-//    Output(calldepth int, s string) error
-//
+//	Output(calldepth int, s string) error
 func (r *Consumer) SetLogger(l logger, lvl LogLevel) {
 	r.logGuard.Lock()
 	defer r.logGuard.Unlock()
@@ -266,8 +265,7 @@ func (r *Consumer) getLogLevel() LogLevel {
 // of the following interfaces that modify the behavior
 // of the `Consumer`:
 //
-//    DiscoveryFilter
-//
+//	DiscoveryFilter
 func (r *Consumer) SetBehaviorDelegate(cb interface{}) {
 	matched := false
 
@@ -312,7 +310,7 @@ func (r *Consumer) getMaxInFlight() int32 {
 // ChangeMaxInFlight sets a new maximum number of messages this comsumer instance
 // will allow in-flight, and updates all existing connections as appropriate.
 //
-// For example, ChangeMaxInFlight(0) would pause message flow
+// # For example, ChangeMaxInFlight(0) would pause message flow
 //
 // If already connected, it updates the reader RDY state for each connection.
 func (r *Consumer) ChangeMaxInFlight(maxInFlight int) {
@@ -513,13 +511,33 @@ retry:
 	if discoveryFilter, ok := r.behaviorDelegate.(DiscoveryFilter); ok {
 		nsqdAddrs = discoveryFilter.Filter(nsqdAddrs)
 	}
+
+	var successfulNsqdAddrs []string
 	for _, addr := range nsqdAddrs {
 		err = r.ConnectToNSQD(addr)
 		if err != nil && err != ErrAlreadyConnected {
 			r.log(LogLevelError, "(%s) error connecting to nsqd - %s", addr, err)
 			continue
 		}
+		successfulNsqdAddrs = append(successfulNsqdAddrs, addr)
 	}
+
+	// in the event that there are new nsqd addresses, remove the old connections from the connections map
+	for addr := range r.connections {
+		if !inAddrs(successfulNsqdAddrs, addr) {
+			delete(r.connections, addr)
+		}
+	}
+}
+
+func inAddrs(addrs []string, addr string) bool {
+	for _, a := range addrs {
+		if addr == a {
+			return true
+		}
+	}
+
+	return false
 }
 
 // ConnectToNSQDs takes multiple nsqd addresses to connect directly to.
@@ -1109,7 +1127,7 @@ func (r *Consumer) stopHandlers() {
 // AddHandler sets the Handler for messages received by this Consumer. This can be called
 // multiple times to add additional handlers. Handler will have a 1:1 ratio to message handling goroutines.
 //
-// This panics if called after connecting to NSQD or NSQ Lookupd
+// # This panics if called after connecting to NSQD or NSQ Lookupd
 //
 // (see Handler or HandlerFunc for details on implementing this interface)
 func (r *Consumer) AddHandler(handler Handler) {
@@ -1120,7 +1138,7 @@ func (r *Consumer) AddHandler(handler Handler) {
 // takes a second argument which indicates the number of goroutines to spawn for
 // message handling.
 //
-// This panics if called after connecting to NSQD or NSQ Lookupd
+// # This panics if called after connecting to NSQD or NSQ Lookupd
 //
 // (see Handler or HandlerFunc for details on implementing this interface)
 func (r *Consumer) AddConcurrentHandlers(handler Handler, concurrency int) {