Handle unknown instance ID during a config apply operation

internal/resource/resource_service.go

@@ -158,6 +158,10 @@ func (r *ResourceService) ApplyConfig(ctx context.Context, instanceID string) er
 	var instance *mpi.Instance
 	operator := r.instanceOperators[instanceID]
 
+	if operator == nil {
+		return fmt.Errorf("no instance operator found for instance %s", instanceID)
+	}
+
 	for _, resourceInstance := range r.resource.GetInstances() {
 		if resourceInstance.GetInstanceMeta().GetInstanceId() == instanceID {
 			instance = resourceInstance

internal/resource/resource_service_test.go

@@ -240,29 +240,40 @@ func TestResourceService_ApplyConfig(t *testing.T) {
 	ctx := context.Background()
 
 	tests := []struct {
+		instanceID  string
 		reloadErr   error
 		validateErr error
 		expected    error
 		name        string
 	}{
 		{
 			name:        "Test 1: Successful reload",
+			instanceID:  protos.GetNginxOssInstance([]string{}).GetInstanceMeta().GetInstanceId(),
 			reloadErr:   nil,
 			validateErr: nil,
 			expected:    nil,
 		},
 		{
 			name:        "Test 2: Failed reload",
+			instanceID:  protos.GetNginxOssInstance([]string{}).GetInstanceMeta().GetInstanceId(),
 			reloadErr:   fmt.Errorf("something went wrong"),
 			validateErr: nil,
 			expected:    fmt.Errorf("failed to reload NGINX %w", fmt.Errorf("something went wrong")),
 		},
 		{
 			name:        "Test 3: Failed validate",
+			instanceID:  protos.GetNginxOssInstance([]string{}).GetInstanceMeta().GetInstanceId(),
 			reloadErr:   nil,
 			validateErr: fmt.Errorf("something went wrong"),
 			expected:    fmt.Errorf("failed validating config %w", fmt.Errorf("something went wrong")),
 		},
+		{
+			name:        "Test 4: Unknown instance ID",
+			instanceID:  "unknown",
+			reloadErr:   nil,
+			validateErr: nil,
+			expected:    fmt.Errorf("no instance operator found for instance unknown"),
+		},
 	}
 
 	for _, test := range tests {
@@ -283,8 +294,7 @@ func TestResourceService_ApplyConfig(t *testing.T) {
 			}
 			resourceService.resource.Instances = instances
 
-			reloadError := resourceService.ApplyConfig(ctx,
-				protos.GetNginxOssInstance([]string{}).GetInstanceMeta().GetInstanceId())
+			reloadError := resourceService.ApplyConfig(ctx, test.instanceID)
 			assert.Equal(t, test.expected, reloadError)
 		})
 	}