cliflags: deprecate using without --sql-addr

Release note (backward-incompatible change): Using a single TCP port
listener for both RPC (node-node) and SQL client connections is now
deprecated. This capability will be removed in the next version of
CockroachDB. Deployments are invited to perform either one of the
following changes:

- (preferred:) keep port 26257 for SQL, and allocate a new port,
  e.g. 36257, for node-node RPC connections. For example:

       --listen-addr=:36257 --sql-addr=:26257 \
       --join=othernode:36257,othernode:26257

  This will become the default configuration in the next version
  of CockroachDB.

  When using this mode of operation, care should be taken to
  use a `--join` flag that include both the old and new
  port numbers for other nodes, so that no network partition
  occurs during the upgrade.

- (optional:) keep port 26257 for RPC, and allocate a new port,
  e.g. 36257, for SQL connections. For example:

      --listen-addr=:26257 --sql-addr=:36257

  When using this mode of operation, the `--join` flags do not
  need to be modified. However, SQL client apps or the SQL
  load balancer configuration (when in use) should be updated
  to use the new SQL port number.

pkg/cli/cliflags/flags.go

@@ -443,8 +443,6 @@ in a later version.`,
 The address/hostname and port to listen on for intra-cluster
 communication, for example --listen-addr=myhost:26257 or
 --listen-addr=:26257 (listen on all interfaces).
-Unless --sql-addr is also specified, this address is also
-used to accept SQL client connections.
 <PRE>
 
 </PRE>
@@ -462,7 +460,15 @@ example [::1]:26257 or [fe80::f6f2:::]:26257.
 If --advertise-addr is left unspecified, the node will also announce
 this address for use by other nodes. It is strongly recommended to use
 --advertise-addr in cloud and container deployments or any setup where
-NAT is present between cluster nodes.`,
+NAT is present between cluster nodes.
+<PRE>
+
+</PRE>
+Unless --sql-addr is also specified, this address is also
+used to accept SQL client connections. Using --listen-addr
+to specify the SQL address without --sql-addr is a deprecated
+feature.
+`,
 	}
 
 	ServerHost = FlagInfo{
@@ -515,8 +521,6 @@ forwarding is set up on an intermediate firewall/router.`,
 		Description: `
 The hostname or IP address to bind to for SQL clients, for example
 --sql-addr=myhost:26257 or --sql-addr=:26257 (listen on all interfaces).
-If left unspecified, the address specified by --listen-addr will be
-used for both RPC and SQL connections.
 <PRE>
 
 </PRE>
@@ -536,7 +540,14 @@ to use the same port number but separate host addresses.
 
 </PRE>
 An IPv6 address can also be specified with the notation [...], for
-example [::1]:26257 or [fe80::f6f2:::]:26257.`,
+example [::1]:26257 or [fe80::f6f2:::]:26257.
+<PRE>
+
+</PRE>
+If --sql-addr is left unspecified, the address specified by
+--listen-addr will be used for both RPC and SQL connections.
+This default behavior is deprecated; we recommend always
+setting --sql-addr.`,
 	}
 
 	SQLAdvertiseAddr = FlagInfo{

pkg/cli/flags.go

@@ -1046,7 +1046,7 @@ func extraServerFlagInit(cmd *cobra.Command) error {
 		serverSQLPort = serverListenPort
 	}
 	serverCfg.SQLAddr = net.JoinHostPort(serverSQLAddr, serverSQLPort)
-	serverCfg.SplitListenSQL = fs.Lookup(cliflags.ListenSQLAddr.Name).Changed
+	serverCfg.SplitListenSQL = changed(fs, cliflags.ListenSQLAddr.Name)
 
 	// Fill in the defaults for --advertise-sql-addr, if the flag exists on `cmd`.
 	advSpecified := changed(fs, cliflags.AdvertiseAddr.Name) ||

pkg/cli/start.go

@@ -1076,17 +1076,23 @@ func expandTabsInRedactableBytes(s redact.RedactableBytes) (redact.RedactableByt
 func hintServerCmdFlags(ctx context.Context, cmd *cobra.Command) {
 	pf := cliflagcfg.FlagSetForCmd(cmd)
 
+	sqlAddrSpecified := pf.Lookup(cliflags.ListenSQLAddr.Name).Changed
+	if !sqlAddrSpecified {
+		log.Ops.Shoutf(ctx, severity.WARNING,
+			"Running a server without --sql-addr, with a combined RPC/SQL listener, is deprecated.\n"+
+				"This feature will be removed in the next version of CockroachDB.")
+	}
+
 	listenAddrSpecified := pf.Lookup(cliflags.ListenAddr.Name).Changed || pf.Lookup(cliflags.ServerHost.Name).Changed
 	advAddrSpecified := pf.Lookup(cliflags.AdvertiseAddr.Name).Changed || pf.Lookup(cliflags.AdvertiseHost.Name).Changed
-
 	if !listenAddrSpecified && !advAddrSpecified {
 		host, _, _ := net.SplitHostPort(serverCfg.AdvertiseAddr)
 		log.Ops.Shoutf(ctx, severity.WARNING,
 			"neither --listen-addr nor --advertise-addr was specified.\n"+
 				"The server will advertise %q to other nodes, is this routable?\n\n"+
 				"Consider using:\n"+
-				"- for local-only servers:  --listen-addr=localhost\n"+
-				"- for multi-node clusters: --advertise-addr=<host/IP addr>\n", host)
+				"- for local-only servers:  --listen-addr=localhost:26258 --sql-addr=localhost:26257\n"+
+				"- for multi-node clusters: --listen-addr=:26258 --sql-addr=:26257 --advertise-addr=<host/IP addr>\n", host)
 	}
 }