reconcile_bad

reconcile_good.go

// controller/sidecar_controller.go

func (r *SidecarReconciler) Reconcile(
	ctx context.Context, req ctrl.Request) (ctrl.Result, error) {

	// STEP 1: get the deployment object
	deployment := &appsv1.Deployment{}
	err := r.Get(ctx, req.NamespacedName, deployment)
	if err != nil {
		return ctrl.Result{}, err
	}

	// STEP 2: reconcile (BAD WAY TO WRITE CODE)

	labels := deployment.GetLabels()

	sidecar := &corev1.Container{
		Name:    sidecarName,
		Image:   sidecarImage,
		Command: []string{"sleep"},
		Args:    []string{"36000"},
	}

	desiredDeployment := deployment.DeepCopy()
	containers := deployment.Spec.Template.Spec.Containers
	// check if inject label present
	if labels[sidecarInjectLabel] == "true" {

		// add sidecar
		containers = append(containers, *sidecar)
		desiredDeployment.Spec.Template.Spec.Containers = containers

		// update
		err := r.Update(ctx, desiredDeployment)
		if err != nil {
			return ctrl.Result{}, err
		}
		return ctrl.Result{}, nil
	}
	for i, container := range containers {
		if container.Name == sidecarName &&
			container.Image == sidecarImage {

			// remove sidecar
			desiredContainers := append(containers[:i], containers[i+1:]...)
			desiredDeployment.Spec.Template.Spec.Containers = desiredContainers

			// update
			err := r.Update(ctx, desiredDeployment)
			if err != nil {
				return ctrl.Result{}, err
			}
			return ctrl.Result{}, nil
		}
	}
	return ctrl.Result{}, nil
}