From f431ef4c9d6c80ed397322c6d6e7b9e5dc7e237f Mon Sep 17 00:00:00 2001
From: Jonathan Mercier-Ganady <jonathan.mercier.ganady@ably.com>
Date: Fri, 9 Oct 2020 10:34:15 +0100
Subject: [PATCH 1/2] Simplify GetListenPort

---
 server/server.go | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/server/server.go b/server/server.go
index b66993a4..25e8d20c 100644
--- a/server/server.go
+++ b/server/server.go
@@ -264,12 +264,7 @@ func (s *Server) IsRunning() bool {
 func (s *Server) GetListenPort() int {
 	s.mu.RLock()
 	defer s.mu.RUnlock()
-
-	if s.listener == nil {
-		return 0
-	}
-
-	return s.listener.Addr().(*net.TCPAddr).Port
+	return s.port
 }
 
 // recoverAndPersistState recovers any existing server metadata state from disk

From 2d5d2a8f0cf4c70413149421803a98dc36f8f440 Mon Sep 17 00:00:00 2001
From: Jonathan Mercier-Ganady <jonathan.mercier.ganady@ably.com>
Date: Fri, 9 Oct 2020 10:52:48 +0100
Subject: [PATCH 2/2] Use the listen port in case the connection port is 0 Note
 that this is using the server's listen port, not the listen host/port set in
 the configuration.

---
 server/metadata.go |  2 +-
 server/server.go   | 18 +++++++++++++++++-
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/server/metadata.go b/server/metadata.go
index 605ec1f7..0b1b1654 100644
--- a/server/metadata.go
+++ b/server/metadata.go
@@ -209,7 +209,7 @@ func (m *metadataAPI) brokerCache(serverIDs map[string]struct{}) ([]*client.Brok
 // argument is the expected number of peers to get a response from.
 func (m *metadataAPI) fetchBrokerInfo(ctx context.Context, numPeers int) ([]*client.Broker, *status.Status) {
 	// Add ourselves.
-	connectionAddress := m.config.GetConnectionAddress()
+	connectionAddress := m.getConnectionAddress()
 	brokers := []*client.Broker{{
 		Id:   m.config.Clustering.ServerID,
 		Host: connectionAddress.Host,
diff --git a/server/server.go b/server/server.go
index 25e8d20c..71cee0ba 100644
--- a/server/server.go
+++ b/server/server.go
@@ -267,6 +267,22 @@ func (s *Server) GetListenPort() int {
 	return s.port
 }
 
+// getConnectionAddress returns the connection address that should be used by
+// the server. It uses the port the server is currently listening to if the
+// connection port is 0, so that an OS-assigned port can be used as a connection
+// port.
+func (s *Server) getConnectionAddress() HostPort {
+	s.mu.RLock()
+	defer s.mu.RUnlock()
+
+	address := s.config.GetConnectionAddress()
+	if address.Port == 0 {
+		address.Port = s.port
+	}
+
+	return address
+}
+
 // recoverAndPersistState recovers any existing server metadata state from disk
 // to initialize the server then writes the metadata back to disk.
 func (s *Server) recoverAndPersistState() error {
@@ -814,7 +830,7 @@ func (s *Server) handleServerInfoRequest(m *nats.Msg) {
 		return
 	}
 
-	connectionAddress := s.config.GetConnectionAddress()
+	connectionAddress := s.getConnectionAddress()
 	data, err := proto.MarshalServerInfoResponse(&proto.ServerInfoResponse{
 		Id:   s.config.Clustering.ServerID,
 		Host: connectionAddress.Host,