How to display column using a fraction format (i.e. X/Y) for CR

[googs1025]

For a custom resource object, I want to use the kubectl method (X/Y) to display the Ready field. I tried it and it shows empty.

// +genclient
...
//+kubebuilder:printcolumn:name="Ready",type="string",JSONPath=".status.readyReplicas + '/' + .spec.replicas",description="Ratio of ready replicas to desired replicas."
//+kubebuilder:printcolumn:name="UP-TO-DATE",type="string",JSONPath=".status.updatedReplicas",description="Number of groups that have been updated (ready or not)."
//+kubebuilder:printcolumn:name="Age",JSONPath=".metadata.creationTimestamp",type=date,description="Age is the time LeaderWorkerSet was created."

// LeaderWorkerSet is the Schema for the leaderworkersets API
type LeaderWorkerSet struct {
	...
}

root@VM-0-8-ubuntu:/home/ubuntu/lws/config/samples# kubectl get lws
NAME                     READY   UP-TO-DATE   AGE
leaderworkerset-sample           3            6s

My expectation is 3/3. like this

root@VM-0-8-ubuntu:/home/ubuntu/lws/config/samples# kubectl get lws
NAME                     READY   UP-TO-DATE   AGE
leaderworkerset-sample    3/3       3            6s

[googs1025]

#2285
I found similar questions, but they don't seem to be solved

[camilamacedo86]

Could you please explain what is not answer?
Did you tried the example?
what are you facing ?
What do you expected instead?

[camilamacedo86]

Can you try to do like JSONPath={.spec.ready}/{.spec.total}` and see if that will output as you expected?

[googs1025]

// +genclient
//+kubebuilder:object:root=true
//+kubebuilder:subresource:status
//+kubebuilder:subresource:scale:specpath=.spec.replicas,statuspath=.status.replicas,selectorpath=.status.hpaPodSelector
//+kubebuilder:resource:shortName={lws}
//+kubebuilder:printcolumn:name="Ready",type="string",JSONPath=`{.status.readyReplicas}/{.spec.replicas}`,description="Ratio of ready replicas to desired replicas."
//+kubebuilder:printcolumn:name="UP-TO-DATE",type="string",JSONPath=".status.updatedReplicas",description="Number of groups that have been updated (ready or not)."
//+kubebuilder:printcolumn:name="Age",JSONPath=".metadata.creationTimestamp",type=date,description="Age is the time LeaderWorkerSet was created."

// LeaderWorkerSet is the Schema for the leaderworkersets API
type LeaderWorkerSet struct {
        metav1.TypeMeta   `json:",inline"`
        metav1.ObjectMeta `json:"metadata,omitempty"`

        Spec   LeaderWorkerSetSpec   `json:"spec,omitempty"`
        Status LeaderWorkerSetStatus `json:"status,omitempty"`
}

When I use it, the following error occurs

root@VM-0-8-ubuntu:/home/ubuntu/lws# make uninstall
make: go: Permission denied
test -s /home/ubuntu/lws/bin/controller-gen && /home/ubuntu/lws/bin/controller-gen --version | grep -q v0.16.2 || \
GOBIN=/home/ubuntu/lws/bin go install sigs.k8s.io/controller-tools/cmd/controller-gen@v0.16.2
/home/ubuntu/lws/bin/controller-gen \
	rbac:roleName=manager-role output:rbac:artifacts:config=config/rbac \
	crd:generateEmbeddedObjectMeta=true output:crd:artifacts:config=config/crd/bases \
	webhook output:webhook:artifacts:config=config/webhook \
	paths="./..."
/home/ubuntu/lws/bin/kustomize build config/crd | kubectl delete --ignore-not-found=false -f -
customresourcedefinition.apiextensions.k8s.io "leaderworkersets.leaderworkerset.x-k8s.io" deleted
root@VM-0-8-ubuntu:/home/ubuntu/lws# make install
make: go: Permission denied
test -s /home/ubuntu/lws/bin/controller-gen && /home/ubuntu/lws/bin/controller-gen --version | grep -q v0.16.2 || \
GOBIN=/home/ubuntu/lws/bin go install sigs.k8s.io/controller-tools/cmd/controller-gen@v0.16.2
/home/ubuntu/lws/bin/controller-gen \
	rbac:roleName=manager-role output:rbac:artifacts:config=config/rbac \
	crd:generateEmbeddedObjectMeta=true output:crd:artifacts:config=config/crd/bases \
	webhook output:webhook:artifacts:config=config/webhook \
	paths="./..."
/home/ubuntu/lws/bin/kustomize build config/crd | kubectl create -f -
The CustomResourceDefinition "leaderworkersets.leaderworkerset.x-k8s.io" is invalid: spec.additionalPrinterColumns[0].JSONPath: Invalid value: "{.status.readyReplicas}/{.spec.replicas}": must be a simple json path starting with .
make: *** [Makefile:187: install] Error 1

[camilamacedo86]

Looking at must be a simple json path starting with . then it might not work in this way.
We would need to raise an issue for controller-tools (controller-gen - https://github.com/kubernetes-sigs/controller-tools ) to see if we can add the support for it.

However, can you try to sort it out with:

• include a computed field that directly holds the desired value, like readyReplicasRatio, and then reference that field in the kubebuilder:printcolumn and let us know if that worked out?

Something like

 //+kubebuilder:printcolumn:name="Ready",type="string",JSONPath=".status.readyReplicasRatio",description="desc"

And add the value in the reconciliation like

leaderWorkerSet.Status.ReadyReplicasRatio = fmt.Sprintf(“%d/%d”, leaderWorkerSet.Status.ReadyReplicas, leaderWorkerSet.Spec.Replicas)

We are looking forward to know if that will works.

[googs1025]

Thank you for continuously researching my question! That's really great. Yes, as you mentioned, using the approach you provided can achieve this goal. However, in terms of design, adding such a field just for display purposes is clearly not a good design practice. This kind of display format like (X/Y) is, in my opinion, very useful and there will likely be many projects that could benefit from it. This should be a feature that needs to be implemented.

[camilamacedo86]

Closing this one since an issue was open for controller-tools: kubernetes-sigs/controller-tools#1051
Where it has been discussed and seems that the RFE would need to be added to the https://github.com/kubernetes/apiserver