2 min read | by Jordi Prats
Some kubernetes objects creates and manages other kubernetes objects in order to provide it's functionality. For example, the Deployment object creates a ReplicaSet that in turn creates the desired Pod objects. We can always track down this relationship using kubectl describe but using the tree krew plugin we can see the relationship in a visual way. We can install it like so:
$ kubectl krew install tree Once installed we can see the relationships of any objects by name, for example:
$ kubectl tree deploy pet2cattle NAMESPACE NAME READY REASON AGE kube-system Deployment/pet2cattle - 173d kube-system ├─ReplicaSet/pet2cattle-6459fd5cfd - 7d14h kube-system ├─ReplicaSet/pet2cattle-6958646f9 - 9d kube-system ├─ReplicaSet/pet2cattle-69f9f4c65d - 12d kube-system ├─ReplicaSet/pet2cattle-6f6b9648ff - 18d kube-system ├─ReplicaSet/pet2cattle-786fd7c9d6 - 11d kube-system ├─ReplicaSet/pet2cattle-798578ccc8 - 4d1h kube-system │ └─Pod/pet2cattle-798578ccc8-49pnx True 4d1h kube-system ├─ReplicaSet/pet2cattle-7dbbd9bf7f - 11d kube-system ├─ReplicaSet/pet2cattle-7f9895c54f - 18d kube-system ├─ReplicaSet/pet2cattle-946bcdb57 - 7d14h kube-system ├─ReplicaSet/pet2cattle-bf7575fbd - 13d kube-system └─ReplicaSet/pet2cattle-f94d49cb4 - 18d Here we can see that only one of the ReplicaSet has a pod, that's because all the other are revisions:
$ kubectl describe ReplicaSet/pet2cattle-798578ccc8 | grep revision deployment.kubernetes.io/revision: 124 $ kubectl describe ReplicaSet/pet2cattle-946bcdb57 | grep revision deployment.kubernetes.io/revision: 123 $ kubectl describe ReplicaSet/pet2cattle-6459fd5cfd | grep revision deployment.kubernetes.io/revision: 122 The old ReplicaSet are scaled down to 0 pods:
$ kubectl describe ReplicaSet/pet2cattle-f94d49cb4 | grep ^Repli Replicas: 0 current / 0 desired So just the active ReplicaSet has an active Pod on this moment.
We can also visualize other objects such as Service:
$ kubectl tree svc pet2cattle NAMESPACE NAME READY REASON AGE kube-system Service/pet2cattle - 173d kube-system └─EndpointSlice/pet2cattle-hzjn7 - 173d Or an Ingress, on this example we can see the Certificate objects that it's using:
$ kubectl tree ingresses.v1.networking.k8s.io pet2cattle-https NAMESPACE NAME READY REASON AGE kube-system Ingress/pet2cattle-https - 173d kube-system └─Certificate/k3s-p2c True Ready 173d kube-system ├─CertificateRequest/k3s-p2c-7zl4g True Issued 116d kube-system │ └─Order/k3s-p2c-7zl4g-3064267605 - 116d kube-system ├─CertificateRequest/k3s-p2c-98vv5 True Issued 37h kube-system │ └─Order/k3s-p2c-98vv5-3758948428 - 37h kube-system ├─CertificateRequest/k3s-p2c-flsnr True Issued 173d kube-system │ └─Order/k3s-p2c-flsnr-424107949 - 173d kube-system └─CertificateRequest/k3s-p2c-wwq4n True Issued 63d kube-system └─Order/k3s-p2c-wwq4n-3758948428 - 63d Posted on 14/06/2021