rpk: generate pool of available ports for container start command

src/go/rpk/pkg/cli/cmd/container/start.go

@@ -175,28 +175,22 @@ func startCluster(
 		return err
 	}
 
-	// Start a seed node.
-	seedID := uint(0)
-	seedKafkaPort, err := vnet.GetFreePort()
-	if err != nil {
-		return err
-	}
-	seedProxyPort, err := vnet.GetFreePort()
-	if err != nil {
-		return err
-	}
-	seedSchemaRegPort, err := vnet.GetFreePort()
-	if err != nil {
-		return err
-	}
-	seedRPCPort, err := vnet.GetFreePort()
-	if err != nil {
-		return err
-	}
-	seedMetricsPort, err := vnet.GetFreePort()
+	reqPorts := n * 5 // we need 5 ports per node
+	ports, err := vnet.GetFreePortPool(int(reqPorts))
 	if err != nil {
 		return err
 	}
+
+	// Start a seed node.
+	var (
+		seedID            uint
+		seedKafkaPort     = ports[0]
+		seedProxyPort     = ports[1]
+		seedSchemaRegPort = ports[2]
+		seedRPCPort       = ports[3]
+		seedMetricsPort   = ports[4]
+	)
+
 	seedState, err := common.CreateNode(
 		c,
 		seedID,
@@ -236,26 +230,14 @@ func startCluster(
 	for nodeID := uint(1); nodeID < n; nodeID++ {
 		id := nodeID
 		grp.Go(func() error {
-			kafkaPort, err := vnet.GetFreePort()
-			if err != nil {
-				return err
-			}
-			proxyPort, err := vnet.GetFreePort()
-			if err != nil {
-				return err
-			}
-			schemaRegPort, err := vnet.GetFreePort()
-			if err != nil {
-				return err
-			}
-			rpcPort, err := vnet.GetFreePort()
-			if err != nil {
-				return err
-			}
-			metricsPort, err := vnet.GetFreePort()
-			if err != nil {
-				return err
-			}
+			var (
+				kafkaPort     = ports[0+5*id]
+				proxyPort     = ports[1+5*id]
+				schemaRegPort = ports[2+5*id]
+				rpcPort       = ports[3+5*id]
+				metricsPort   = ports[4+5*id]
+			)
+
 			args := []string{
 				"--seeds",
 				net.JoinHostPort(

src/go/rpk/pkg/cli/cmd/container/start_test.go

@@ -129,7 +129,8 @@ Please check your internet connection and try again.`,
 			expectedErrMsg: "Network create go boom",
 		},
 		{
-			name: "it should fail if inspecting the network fails",
+			name:  "it should fail if inspecting the network fails",
+			nodes: 1,
 			client: func(_ *testing.T) (common.Client, error) {
 				return &common.MockClient{
 					MockNetworkInspect: func(
@@ -147,7 +148,8 @@ Please check your internet connection and try again.`,
 			expectedErrMsg: "Can't inspect the network",
 		},
 		{
-			name: "it should fail if the network config is corrupted",
+			name:  "it should fail if the network config is corrupted",
+			nodes: 1,
 			client: func(_ *testing.T) (common.Client, error) {
 				return &common.MockClient{
 					MockNetworkInspect: func(
@@ -211,7 +213,8 @@ Please check your internet connection and try again.`,
 			expectedErrMsg: "Can't inspect",
 		},
 		{
-			name: "it should fail if creating the container fails",
+			name:  "it should fail if creating the container fails",
+			nodes: 1,
 			client: func(_ *testing.T) (common.Client, error) {
 				return &common.MockClient{
 					// NetworkInspect succeeds returning the

src/go/rpk/pkg/net/interfaces.go

@@ -45,7 +45,7 @@ func GetInterfacesByIps(addresses ...string) ([]string, error) {
 	return utils.GetKeys(nics), nil
 }
 
-func GetFreePort() (uint, error) {
+func getFreePort() (uint, error) {
 	addr, err := net.ResolveTCPAddr("tcp", "localhost:0")
 	if err != nil {
 		return 0, err
@@ -58,3 +58,15 @@ func GetFreePort() (uint, error) {
 	defer l.Close()
 	return uint(l.Addr().(*net.TCPAddr).Port), nil
 }
+
+func GetFreePortPool(n int) ([]uint, error) {
+	var ports []uint
+	for i := 0; i < n; i++ {
+		p, err := getFreePort()
+		if err != nil {
+			return nil, err
+		}
+		ports = append(ports, p)
+	}
+	return ports, nil
+}