为 Pod 标签编写控制器

kubectl label my-pod my-label-key=my-label-value

mkdir label-operator && cd label-operator

# Feel free to change the domain and repo values.
operator-sdk init --domain=padok.fr --repo=github.com/busser/label-operator

operator-sdk create api --group=core --version=v1 --kind=Pod --controller=true --resource=false

func (r *PodReconciler) Reconcile(ctx context.Context, req ctrl.Request) (ctrl.Result, error) {
    _ = r.Log.WithValues("pod", req.NamespacedName)

    // your logic here

    return ctrl.Result{}, nil
}

func (r *PodReconciler) SetupWithManager(mgr ctrl.Manager) error {
    return ctrl.NewControllerManagedBy(mgr).
        // Uncomment the following line adding a pointer to an instance of the controlled resource as an argument
        // For().
        Complete(r)
}

package controllers

import (
    // other imports...
    corev1 "k8s.io/api/core/v1"
    // other imports...
)

func (r *PodReconciler) SetupWithManager(mgr ctrl.Manager) error {
    return ctrl.NewControllerManagedBy(mgr).
        For(&corev1.Pod{}).
        Complete(r)
}

// +kubebuilder:rbac:groups=core,resources=pods,verbs=get;list;watch;create;update;patch;delete
// +kubebuilder:rbac:groups=core,resources=pods/status,verbs=get;update;patch
// +kubebuilder:rbac:groups=core,resources=pods/finalizers,verbs=update

// +kubebuilder:rbac:groups=core,resources=pods,verbs=get;list;watch;update;patch

const (
    addPodNameLabelAnnotation = "padok.fr/add-pod-name-label"
    podNameLabel              = "padok.fr/pod-name"
)

// Reconcile handles a reconciliation request for a Pod.
// If the Pod has the addPodNameLabelAnnotation annotation, then Reconcile
// will make sure the podNameLabel label is present with the correct value.
// If the annotation is absent, then Reconcile will make sure the label is too.
func (r *PodReconciler) Reconcile(ctx context.Context, req ctrl.Request) (ctrl.Result, error) {
    log := r.Log.WithValues("pod", req.NamespacedName)

    /*
        Step 0: Fetch the Pod from the Kubernetes API.
    */

    var pod corev1.Pod
    if err := r.Get(ctx, req.NamespacedName, &pod); err != nil {
        log.Error(err, "unable to fetch Pod")
        return ctrl.Result{}, err
    }

    return ctrl.Result{}, nil
}

package controllers

import (
    // other imports...
    apierrors "k8s.io/apimachinery/pkg/api/errors"
    // other imports...
)

    /*
        Step 0: Fetch the Pod from the Kubernetes API.
    */

    var pod corev1.Pod
    if err := r.Get(ctx, req.NamespacedName, &pod); err != nil {
        if apierrors.IsNotFound(err) {
            // we'll ignore not-found errors, since we can get them on deleted requests.
            return ctrl.Result{}, nil
        }
        log.Error(err, "unable to fetch Pod")
        return ctrl.Result{}, err
    }

    /*
        Step 1: Add or remove the label.
    */

    labelShouldBePresent := pod.Annotations[addPodNameLabelAnnotation] == "true"
    labelIsPresent := pod.Labels[podNameLabel] == pod.Name

    if labelShouldBePresent == labelIsPresent {
        // The desired state and actual state of the Pod are the same.
        // No further action is required by the operator at this moment.
        log.Info("no update required")
        return ctrl.Result{}, nil
    }

    if labelShouldBePresent {
        // If the label should be set but is not, set it.
        if pod.Labels == nil {
            pod.Labels = make(map[string]string)
        }
        pod.Labels[podNameLabel] = pod.Name
        log.Info("adding label")
    } else {
        // If the label should not be set but is, remove it.
        delete(pod.Labels, podNameLabel)
        log.Info("removing label")
    }

    /*
        Step 2: Update the Pod in the Kubernetes API.
    */

    if err := r.Update(ctx, &pod); err != nil {
        log.Error(err, "unable to update Pod")
        return ctrl.Result{}, err
    }

    /*
        Step 2: Update the Pod in the Kubernetes API.
    */

    if err := r.Update(ctx, &pod); err != nil {
        if apierrors.IsConflict(err) {
            // The Pod has been updated since we read it.
            // Requeue the Pod to try to reconciliate again.
            return ctrl.Result{Requeue: true}, nil
        }
        if apierrors.IsNotFound(err) {
            // The Pod has been deleted since we read it.
            // Requeue the Pod to try to reconciliate again.
            return ctrl.Result{Requeue: true}, nil
        }
        log.Error(err, "unable to update Pod")
        return ctrl.Result{}, err
    }

    return ctrl.Result{}, nil
}

make run

kubectl run --image=nginx my-nginx

INFO    controllers.Pod no update required  {"pod": "default/my-nginx"}
INFO    controllers.Pod no update required  {"pod": "default/my-nginx"}
INFO    controllers.Pod no update required  {"pod": "default/my-nginx"}
INFO    controllers.Pod no update required  {"pod": "default/my-nginx"}

kubectl annotate pod my-nginx padok.fr/add-pod-name-label=true

INFO    controllers.Pod adding label    {"pod": "default/my-nginx"}