Apply a local package
Topics
Because kpt packages are composed of resource configuration, they can be
applied with kubectl apply -R -f DIR. However, kpt includes the
next-generation apply commands developed out of the Kubernetes cli-utils
repository as the kpt live apply command.
Kpt live apply provides additional functionality beyond what is provided by
kubectl apply, such as communicating back resource status and pruning
resources for deleted configuration.
Steps
- Fetch a remote package
- Initialize the package inventory template
- Apply to a cluster
- Print the live resources
- Prune resources
Fetch a remote package
Command
export SRC_REPO=https://github.com/GoogleContainerTools/kpt.git
kpt pkg get $SRC_REPO/package-examples/helloworld-set@v0.5.0 helloworld
Grab a remote package to apply to a cluster.
Output
fetching package /package-examples/helloworld-set from https://github.com/GoogleContainerTools/kpt to helloworld
Initialize the package inventory template
The kpt version of apply uses a ConfigMap map to keep track of previously applied resources so they can be pruned later if the configuration for them is deleted. The kpt live init command will generate an inventory template (which is just a normal ConfigMap manifest with a special annotation) used by kpt live apply to generate an actual ConfigMap in the cluster which we refer to as an inventory object.
The inventory template must be created for a package to be applied using
kpt live apply.
Init Command
kpt live init helloworld
Init Output
namespace: default is used for inventory object
Initialized: helloworld/inventory-template.yaml
Inventory template
apiVersion: v1
kind: ConfigMap
metadata:
...
name: inventory
labels:
# DANGER: Do not change the value of this label.
# Changing this value will cause a loss of continuity
# with previously applied inventory objects. Set deletion
# and pruning functionality will be impaired.
cli-utils.sigs.k8s.io/inventory-id: 060da2f6-dc0e-4425-a286-9a4acbad063d
A ConfigMap with the cli-utils.sigs.k8s.io/inventory-id label has been
created, and will be used by apply to generate a history of previously
applied resources. This file should be checked into git along with the
rest of the package, but otherwise ignored by users.
Apply to a cluster
Apply Command
kpt live apply helloworld --reconcile-timeout=2m
Apply the resources to the cluster and block until the changes have been fully rolled out – e.g. until the Pods are running.
Apply Output
configmap/inventory-17c4dd3c created
service/helloworld-gke created
deployment.apps/helloworld-gke created
3 resource(s) applied. 3 created, 0 unchanged, 0 configured
configmap/inventory-2911da3b is Current: Resource is always ready
service/helloworld-gke is Current: Service is ready
deployment.apps/helloworld-gke is InProgress: Available: 0/5
deployment.apps/helloworld-gke is InProgress: Available: 2/5
deployment.apps/helloworld-gke is Current: Deployment is available. Replicas: 5
resources failed to the reached Current status
0 resource(s) pruned
Apply prints the status of the resources as it waits for all changes to be rolled out.
Print the live resources
Display the resources in the cluster using kubectl.
Print Command
kubectl get configmaps,deploy,services
Print Output
NAME DATA AGE
configmap/inventory-28c4kc3c 2 2m47s
NAME READY UP-TO-DATE AVAILABLE AGE
deployment.apps/helloworld-gke 5/5 5 5 2m47s
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
service/helloworld-gke NodePort 10.48.2.143 <none> 80:32442/TCP 2m47s
service/kubernetes ClusterIP 10.48.0.1 <none> 443/TCP 19m
Command: tree
kubectl get all -o yaml | kpt cfg tree
The output of kubectl can also be piped to kpt cfg tree to summarize the resources.
Output: tree
.
├── [Resource] Deployment default/helloworld-gke
│ └── [Resource] ReplicaSet default/helloworld-gke-5bf95f8869
│ ├── [Resource] Pod default/helloworld-gke-5bf95f8869-mm7sq
│ ├── [Resource] Pod default/helloworld-gke-5bf95f8869-ng8kh
│ ├── [Resource] Pod default/helloworld-gke-5bf95f8869-nlh4r
│ ├── [Resource] Pod default/helloworld-gke-5bf95f8869-phx85
│ └── [Resource] Pod default/helloworld-gke-5bf95f8869-v4259
├── [Resource] Service default/helloworld-gke
└── [Resource] Service default/kubernetes
Prune resources
Resources can be deleted from the cluster by deleting the corresponding resource configuration.
Prune Command
rm helloworld/deploy.yaml
kpt live apply helloworld/ --reconcile-timeout=2m
Apply uses the previously created inventory objects (ConfigMaps) to calculate the set of resources to prune (delete) after applying. In this case the Deployment.
Prune Output
service/helloworld-gke is Current: Service is ready
resources failed to the reached Current status
deployment.apps/helloworld-gke pruned
configmap/inventory-2911da3b pruned
2 resource(s) pruned
Print the live resources after pruning
kubectl get deploy
No resources found in default namespace.