Scaling StatefulSet filtered using label selectors

[bhavin192]

Is your enhancement related to a problem? Please describe

I'm trying scale a StatefulSet by selecting it using its labels. For example, kubectl allows following:

$ kubectl scale statefulset -l release=yb,app.kubernetes.io/name=yb-tserver --replicas=4
statefulset.apps/yb-yugabyte-yb-tserver scaled

But when we filter StatefulSets with label selectors, the scale() method is not there.

Describe the solution you'd like

I'm thinking of something similar like this:

client
    .apps()
    .statefulSets()
    .withLabel("release", "yb")
    .withLabel(appLabel, "yb-tserver")
    .scale(4);

Describe alternatives you've considered

So far I have tried using list(), and then getting the first StatefulSet out of it. But when I tried to load the StatefulSet into client, the scale() method was not present. So, I had to use the metadata.name.

StatefulSet sts =
    client
	.apps()
	.statefulSets()
	.withLabel("release", "yb")
	.withLabel(appLabel, "yb-tserver")
	.list()
	.getItems()
	.get(0);

// This was not possible (should I create a separate issue for this?)
client.resource(sts).scale(4);

// I had to do this instead
client
    .apps()
    .statefulSets()
    .withName(sts.getMetadata().getName())
    .scale(4);

Additional context

When kubectl finds multiple StatefulSets filtered the label selectors, it just scales all of them.

$ kubectl scale statefulset -l release=yb --replicas=4
statefulset.apps/yb-yugabyte-yb-master scaled
statefulset.apps/yb-yugabyte-yb-tserver scaled

[shawkins]

// This was not possible (should I create a separate issue for this?)
client.resource(sts).scale(4);

That won't be possible because we don't know the type of Resource to return. At a minimum you'd have to specify
client.resource(sts, RollableScalableResource.class).scale(4); - and then you'd have to cast to RollableScalableResource<StatefulSet>

Alternatively fabric8 6 will support:

client.apps().statefulSets().withItem(sts).scale(4);

@manusa @rohanKanojia is resource a better method name than withItem here?

For now you would do something like:

var statefulSets = client.apps().statefulSets();
statefulSets
  .withLabel("release", "yb")
  .withLabel(appLabel, "yb-tserver")
  .list().getItems()
  .forEach(s -> statefulSets.withName(s.getName()).scale(4));

I think we can easily make that better with an enhancement that would add a resourceList or similar method that would return a List of the Resource subclasses:

var statefulSets = client.apps().statefulSets();
statefulSets
  .withLabel("release", "yb")
  .withLabel(appLabel, "yb-tserver")
  .resourceList().forEach(s -> s.scale(4));

[bhavin192]

That won't be possible because we don't know the type of Resource to return. At a minimum you'd have to specify
client.resource(sts, RollableScalableResource.class).scale(4); - and then you'd have to cast to RollableScalableResource

Alternatively fabric8 6 will support:

client.apps().statefulSets().withItem(sts).scale(4);

Right, that makes sense. This new method seems to be useful.

Thank you for the forEach idea, that gives us same behavior as kubectl scale. forEach didn't come to my mind as I'm not much used to writing Java 😄

Does it makes sense to add an example for this in the docs/examples directory (I can add it if we agree to do so).

[shawkins]

Does it makes sense to add an example for this in the docs/examples directory (I can add it if we agree to do so).

Yes, an example would be good. Then either this issue or a new one could be for adding a resourceList method to clean this up a bit.

[shawkins]

a resources method was added with #3973

client.apps().statefulSets()
  .withLabel("release", "yb")
  .withLabel(appLabel, "yb-tserver")
  .resources()
  .forEach(s -> s.scale(4));

[bhavin192]

That's great, thanks! I have been away for a while, I will send PR for docs/example entry next week. With my PR we can close this issue.