Resolve "Failed network element creation leads to the return of false error messages"

Typos in combination with copy paste resulted in the return of faulty error messages after cleaning up plugins in the addMne method of controller/northbound/server/networkelement.go.

Description

The clean up of plugins after something went wrong while creating a managed network element, has been moved into a defer function. So if an error is thrown and a plugin has already been created and started, the defer function will stop the plugin and remove the corresponding files.

Related Issue

#330

Motivation and Context

How Has This Been Tested?

Created network elements within the controller, that failed in the process.

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

controller/northbound/server/networkElement.go

@@ -24,6 +24,7 @@ import (
 	aGNMI "code.fbi.h-da.de/danet/gosdn/forks/goarista/gnmi"
 	"github.com/bufbuild/protovalidate-go"
 	"github.com/google/uuid"
+	"github.com/hashicorp/go-multierror"
 	"github.com/openconfig/gnmi/proto/gnmi"
 
 	"github.com/openconfig/ygot/ygot"
@@ -568,8 +569,18 @@ func (n *NetworkElementServer) AddList(ctx context.Context, request *mnepb.AddLi
 	}, nil
 }
 
-func (n *NetworkElementServer) addMne(ctx context.Context, name string, opt *tpb.TransportOption, requestPluginFunc func(uuid.UUID) (plugin.Plugin, error), pluginID uuid.UUID, pndID uuid.UUID, optionalNetworkElementID ...uuid.UUID) (uuid.UUID, error) {
-	var err error
+func (n *NetworkElementServer) addMne(ctx context.Context, name string, opt *tpb.TransportOption, requestPluginFunc func(uuid.UUID) (plugin.Plugin, error), pluginID uuid.UUID, pndID uuid.UUID, optionalNetworkElementID ...uuid.UUID) (mneId uuid.UUID, err error) {
+	var plugin plugin.Plugin
+	var mne networkelement.NetworkElement
+
+	defer func() {
+		if err != nil && plugin != nil {
+			// clean up plugin
+			if pErr := plugin.Remove(); pErr != nil {
+				err = multierror.Append(err, pErr)
+			}
+		}
+	}()
 
 	networkElementID := uuid.Nil
 	if len(optionalNetworkElementID) > 0 {
@@ -580,38 +591,29 @@ func (n *NetworkElementServer) addMne(ctx context.Context, name string, opt *tpb
 		requestPluginFunc = n.pluginService.RequestPlugin
 	}
 
-	plugin, err := requestPluginFunc(pluginID)
+	plugin, err = requestPluginFunc(pluginID)
 	if err != nil {
 		return uuid.Nil, err
 	}
 
-	mne, err := nucleus.NewNetworkElement(name, networkElementID, opt, pndID, plugin, conflict.Metadata{ResourceVersion: 0})
+	mne, err = nucleus.NewNetworkElement(name, networkElementID, opt, pndID, plugin, conflict.Metadata{ResourceVersion: 0})
 	if err != nil {
-		if pluginRmErr := plugin.Remove(); err != nil {
-			return uuid.Nil, pluginRmErr
-		}
 		return uuid.Nil, err
 	}
 
 	if mne.IsTransportValid() {
-		err := n.initialNetworkElementRootPathRequest(ctx, mne, plugin)
+		err = n.initialNetworkElementRootPathRequest(ctx, mne, plugin)
 		if err != nil {
 			return uuid.Nil, err
 		}
 
 		err = n.mneService.Add(mne)
 		if err != nil {
-			if pluginRmErr := plugin.Remove(); err != nil {
-				return uuid.Nil, pluginRmErr
-			}
 			return uuid.Nil, err
 		}
 
 		err = n.pluginService.Add(plugin)
 		if err != nil {
-			if pluginRmErr := plugin.Remove(); err != nil {
-				return uuid.Nil, pluginRmErr
-			}
 			if err := n.mneService.Delete(mne); err != nil {
 				return uuid.Nil, err
 			}
@@ -620,10 +622,8 @@ func (n *NetworkElementServer) addMne(ctx context.Context, name string, opt *tpb
 
 		n.networkElementWatchter.SubscribeToNetworkElement(mne, config.GetGnmiSubscriptionPaths(), nil)
 	} else {
-		if pluginRmErr := plugin.Remove(); err != nil {
-			return uuid.Nil, pluginRmErr
-		}
-		return uuid.Nil, fmt.Errorf("invalid transport data provided")
+		err = fmt.Errorf("invalid transport data provided")
+		return uuid.Nil, err
 	}
 
 	return mne.ID(), nil
@@ -632,17 +632,11 @@ func (n *NetworkElementServer) addMne(ctx context.Context, name string, opt *tpb
 func (n *NetworkElementServer) initialNetworkElementRootPathRequest(ctx context.Context, mne networkelement.NetworkElement, plugin plugin.Plugin) error {
 	resp, err := n.getPath(ctx, mne, "/")
 	if err != nil {
-		if pluginRmErr := plugin.Remove(); err != nil {
-			return pluginRmErr
-		}
 		return err
 	}
 
 	err = mne.ProcessResponse(resp)
 	if err != nil {
-		if pluginRmErr := plugin.Remove(); err != nil {
-			return pluginRmErr
-		}
 		return err
 	}
 	return nil