Get first element of a map when using kubectl get ... -o template - kubectl

Question

I have a service and I would like to get an IP from its spec, using -o go-template I can do it that way:
kubectl get service webapp1-loadbalancer-svc -o go-template='{{(index .status.loadBalancer.ingress 0).ip}}'
This returns the IP of the first ingress in the load balancer which is what I want.
However, instead of using -o go-template, I would like to use -o template. I have tried multiple commands but I am unable to do so. The closest thing I have working is:
kubectl get service webapp1-loadbalancer-svc -o template={{.status.loadBalancer.ingress}}
But this returns the map [map[ip:172.17.0.28]], not just the IP. Everything I have tried to get the IP in the same command is returning errors while executing the template.
Is there a way to obtain the IP from the map using one kubectl command using -o template instead of -o go-template?

Answer 1

Kubectl supports JSONPath template.
Using JsonPath you can retrieve service cluster IP or other details as below.
ubuntu#k8s-master:~$ kubectl get all -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
pod/nginx 1/1 Running 0 129m 192.168.85.226 k8s-node01 <none> <none>
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR
service/kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 2d2h <none>
service/nginx ClusterIP 10.96.184.196 <none> 80/TCP 11m run=nginx
ubuntu#k8s-master:~$ kubectl get service nginx -o jsonpath='{.spec.clusterIP}'
10.96.184.196
Using JsonPath Works well with LoadBlancer type as well .. hope this is what you want to work with.
$ kubectl get all -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
pod/nginx 1/1 Running 0 133m 192.168.85.226 k8s-node01 <none> <none>
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR
service/kubernetes ClusterIP 10.96.0.1 <none> 443/TCP 2d2h <none>
service/nginx LoadBalancer 10.100.165.17 <pending> 80:30852/TCP 5s run=nginx
ubuntu#k8s-master:~$
10.100.165.17ubuntu#k8s-master:~$ kubectl get service nginx -o jsonpath='{.spec.type}'
LoadBalancer
ubuntu#k8s-master:~$ kubectl get service nginx -o jsonpath='{.spec.clusterIP}'
10.100.165.17
So when you extract PORTs it also return a map as below
$ kubectl get service nginx -o jsonpath='{.spec.ports}'
[map[nodePort:30852 port:80 protocol:TCP targetPort:80]]
you can extract the nodePort, port and targetPort each as as below
$ kubectl get service nginx -o jsonpath='{.spec.ports[].targetPort}'
80
ubuntu#k8s-master:~$ kubectl get service nginx -o jsonpath='{.spec.ports[].nodePort}'
30852
ubuntu#k8s-master:~$ kubectl get service nginx -o jsonpath='{.spec.ports[].port}'
80
Hope above examples will help you fix your query
I think you should be able to do by this command when using jsonpath.
kubectl get service webapp1-loadbalancer-svc -o jsonpath={{.status.loadBalancer.ingress[].ip}}