Create only network that are used

- default network is only created if needed
- it's possible to override default network configuration

Signed-off-by: Vincent Demeester <vincent@sbr.pm>

cli/command/stack/deploy.go

@@ -122,7 +122,8 @@ func deployCompose(ctx context.Context, dockerCli *command.DockerCli, opts deplo
 
 	namespace := namespace{name: opts.namespace}
 
-	networks, externalNetworks := convertNetworks(namespace, config.Networks)
+	serviceNetworks := getServicesDeclaredNetworks(config.Services)
+	networks, externalNetworks := convertNetworks(namespace, config.Networks, serviceNetworks)
 	if err := validateExternalNetworks(ctx, dockerCli, externalNetworks); err != nil {
 		return err
 	}
@@ -135,6 +136,19 @@ func deployCompose(ctx context.Context, dockerCli *command.DockerCli, opts deplo
 	}
 	return deployServices(ctx, dockerCli, services, namespace, opts.sendRegistryAuth)
 }
+func getServicesDeclaredNetworks(serviceConfigs []composetypes.ServiceConfig) map[string]struct{} {
+	serviceNetworks := map[string]struct{}{}
+	for _, serviceConfig := range serviceConfigs {
+		if len(serviceConfig.Networks) == 0 {
+			serviceNetworks["default"] = struct{}{}
+			continue
+		}
+		for network := range serviceConfig.Networks {
+			serviceNetworks[network] = struct{}{}
+		}
+	}
+	return serviceNetworks
+}
 
 func propertyWarnings(properties map[string]string) string {
 	var msgs []string
@@ -181,18 +195,17 @@ func getConfigFile(filename string) (*composetypes.ConfigFile, error) {
 func convertNetworks(
 	namespace namespace,
 	networks map[string]composetypes.NetworkConfig,
+	servicesNetworks map[string]struct{},
 ) (map[string]types.NetworkCreate, []string) {
 	if networks == nil {
 		networks = make(map[string]composetypes.NetworkConfig)
 	}
 
-	// TODO: only add default network if it's used
-	networks["default"] = composetypes.NetworkConfig{}
-
 	externalNetworks := []string{}
 	result := make(map[string]types.NetworkCreate)
 
-	for internalName, network := range networks {
+	for internalName := range servicesNetworks {
+		network := networks[internalName]
 		if network.External.External {
 			externalNetworks = append(externalNetworks, network.External.Name)
 			continue