I need to watch (and wait) until a POD is deleted. I need to this is because I need to start a second pod (with the same name) immediately after the first one has been deleted.
This is what I'm trying:
func (k *k8sClient) waitPodDeleted(ctx context.Context, resName string) error {
watcher, err := k.createPodWatcher(ctx, resName)
if err != nil {
return err
}
defer watcher.Stop()
for {
select {
case event := <-watcher.ResultChan():
if event.Type == watch.Deleted {
k.logger.Debugf("The POD \"%s\" is deleted", resName)
return nil
}
case <-ctx.Done():
k.logger.Debugf("Exit from waitPodDeleted for POD \"%s\" because the context is done", resName)
return nil
}
}
}
The problem with this approach is that when I get the Deleted event, is when the POD receives the event for deletion, but not when it is actually deleted. Doing some extra tests I ended debugging the process with this code:
case event := <-watcher.ResultChan():
if event.Type == watch.Deleted {
pod := event.Object.(*v1.Pod)
k.logger.Debugf("EVENT %s PHASE %s MESSAGE %s", event.Type, pod.Status.Phase, pod.Status.Message)
}
The log result for this is:
2022-02-15T08:21:51 DEBUG EVENT DELETED PHASE Running MESSAGE
2022-02-15T08:22:21 DEBUG EVENT DELETED PHASE Running MESSAGEI'm getting two Deleted events. The first one right away I send the delete command. The last one when the pod is effectively deleted from the cluster.
My questions are:
The usecase I'm trying to solve: In my application there is a feature to replace a tool with another with different options. The feature needs to delete the pod that contains the tool and relaunch it with another set of options. In this scenario I need to wait for the pod deletion so I can start it again.
Thanks in advance!
As I said in the comments, the real problem was the watcher I was creating to watch the pod I want to get deleted. In the watcher I was creating a LabelSelector that was selecting two pods instead of one. This is the complete solution, including the watcher.
func (k *k8sClient) createPodWatcher(ctx context.Context, resName string) (watch.Interface, error) {
labelSelector := fmt.Sprintf("app.kubernetes.io/instance=%s", resName)
k.logger.Debugf("Creating watcher for POD with label: %s", labelSelector)
opts := metav1.ListOptions{
TypeMeta: metav1.TypeMeta{},
LabelSelector: labelSelector,
FieldSelector: "",
}
return k.clientset.CoreV1().Pods(k.cfg.Kubernetes.Namespace).Watch(ctx, opts)
}
func (k *k8sClient) waitPodDeleted(ctx context.Context, resName string) error {
watcher, err := k.createPodWatcher(ctx, resName)
if err != nil {
return err
}
defer watcher.Stop()
for {
select {
case event := <-watcher.ResultChan():
if event.Type == watch.Deleted {
k.logger.Debugf("The POD \"%s\" is deleted", resName)
return nil
}
case <-ctx.Done():
k.logger.Debugf("Exit from waitPodDeleted for POD \"%s\" because the context is done", resName)
return nil
}
}
}
func (k *k8sClient) waitPodRunning(ctx context.Context, resName string) error {
watcher, err := k.createPodWatcher(ctx, resName)
if err != nil {
return err
}
defer watcher.Stop()
for {
select {
case event := <-watcher.ResultChan():
pod := event.Object.(*v1.Pod)
if pod.Status.Phase == v1.PodRunning {
k.logger.Infof("The POD \"%s\" is running", resName)
return nil
}
case <-ctx.Done():
k.logger.Debugf("Exit from waitPodRunning for POD \"%s\" because the context is done", resName)
return nil
}
}
}