Resolve "Requesting information from the Controller via NBI takes very long"

Description

Related Issue

#230 (closed)

Motivation and Context

How Has This Been Tested?

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.

cli/adapter/PndAdapter.go

@@ -75,7 +75,8 @@ func (p *PndAdapter) GetDevice(ctx context.Context, identifier string) (*ppb.Get
 }
 
 // GetDevices requests all devices belonging to the PrincipalNetworkDomain
-// attached to this adapter.
+// attached to this adapter. The requested devices also contain their config
+// information as gNMI notifications.
 func (p *PndAdapter) GetDevices(ctx context.Context) (*ppb.GetOndListResponse, error) {
 	resp, err := api.GetDevices(ctx, p.endpoint, p.id.String())
 	if err != nil {
@@ -84,6 +85,17 @@ func (p *PndAdapter) GetDevices(ctx context.Context) (*ppb.GetOndListResponse, e
 	return resp, nil
 }
 
+// GetFlattenedDevices requests all devices belonging to the PrincipalNetworkDomain
+// attached to this adapter. The devices do not contain the config information
+// as gNMI notifications.
+func (p *PndAdapter) GetFlattenedDevices(ctx context.Context) (*ppb.GetFlattenedOndListResponse, error) {
+	resp, err := api.GetFlattenedDevices(ctx, p.endpoint, p.id.String())
+	if err != nil {
+		return nil, err
+	}
+	return resp, nil
+}
+
 // RemoveDevice removes a device from the controller
 func (p *PndAdapter) RemoveDevice(ctx context.Context, did uuid.UUID) (*ppb.DeleteOndResponse, error) {
 	resp, err := api.DeleteDevice(ctx, p.endpoint, p.id.String(), did.String())