Getting Started with kapp

Tiffany Jernigan

kapp (part of the open source Carvel suite) is a lightweight application-centric tool for deploying resources on Kubernetes. Being both explicit and application-centric it provides an easier way to deploy and view all resources created together regardless of what namespace they’re in. Being dependency-aware, it is able to wait for resources to be created, updated, or deleted, and provides a live status on the progress of the actions. Continue on to see how to get started with kapp.

Prerequisites

Before you get started you will need to do the following:

Create a Kubernetes cluster
Install kubectl locally
Install the kapp CLI via one of these options:
- Homebrew:
```
brew tap vmware-tanzu/carvel
brew install kapp
```
- GitHub releases: move the binary to /usr/local/bin or add it to your $PATH and run chmod +x to make it executable

Note: This guide uses kapp v0.37.0, and we suggest you download and install the same version to ensure the best experience as you follow through this guide.

Deploy App

Let’s go ahead and deploy our first application with kapp!

First Run

Create a namespace to use as a state namespace:
```
kubectl create namespace kapp-demo
```
The state namespace is the namespace kapp uses for state storage.

Create kapp-spring-petclinic.yaml file with a Spring PetClinic namespace, deployment, and service:

cat <<EOF > kapp-spring-petclinic.yaml
---
apiVersion: v1
kind: Namespace
metadata:
  name: spring-petclinic
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: spring-petclinic
  namespace: spring-petclinic
spec:
  selector:
    matchLabels:
      app: spring-petclinic
  replicas: 2
  template:
    metadata:
      labels:
        app: spring-petclinic
    spec:
      containers:
      - name: spring-petclinic
        image: springcommunity/spring-framework-petclinic
        ports:
        - name: http
          containerPort: 8080
---
apiVersion: v1
kind: Service
metadata:
  name: spring-petclinic
  namespace: spring-petclinic
  labels:
    app: spring-petclinic
spec:
  ports:
  - port: 80
    protocol: TCP
    targetPort: 8080
  selector:
    app: spring-petclinic
  type: ClusterIP
EOF

Here is where kapp gets involved. We will use it to create our deployment and service.
```
kapp deploy -n kapp-demo -a spring-petclinic -f kapp-spring-petclinic.yaml
```
This format is fairly similar to kubectl apply -f kapp-spring-petclinic.yaml, but it also has an application name. You can also provide a directory instead of a single file.

The next difference you will notice is it prompts you if you want to actually run the command. You can shortcut this by adding the -y flag.

It should give you an output similar to the following before hit y.
```
Target cluster 'https://35.247.3.14' (nodes: demo-default-pool-0f8526ab-rb7b, 2+)

Changes

Namespace         Name              Kind        Conds.  Age  Op      Op st.  Wait to    Rs  Ri
(cluster)         spring-petclinic  Namespace   -       -    create  -       reconcile  -   -  
spring-petclinic  spring-petclinic  Deployment  -       -    create  -       reconcile  -   -  
^                 spring-petclinic  Service     -       -    create  -       reconcile  -   -  

Op:      3 create, 0 delete, 0 update, 0 noop
Wait to: 3 reconcile, 0 delete, 0 noop
```
You can see that it’s creating the spring-petclinic namespace, deployment, and service inside that namespace.

Here is a more significant difference with kubectl. kapp will wait on the resources to become available before terminating and will also show the progress for each resource and tell you if it succeeded or failed. Don’t worry, I didn’t set you up for failure :).
Now that we have the deployment and service up, we can verify it’s working properly. First we can just take a look and see that they are up.
```
kubectl -n spring-petclinic get deployment,service spring-petclinic
```
And then we can create a container and curl the service from within it. We need to do this right now since the service type is ClusterIP (default) so we can’t see it from outside of the cluster itself.
```
kubectl run -it --rm --restart=Never curl --image=curlimages/curl spring-petclinic.spring-petclinic.svc.cluster.local
```

Looking At the App with kapp

Okay, so let’s use kapp instead to take a look at our application.

We can take a look at everything we have running with kapp using the following command:
```
kapp list -A
```
If you didn’t run anything else prior, we should just see Spring PetClinic. You will notice here kapp uses kapp-demo as the state namespace. This is separate from the spring-petclinic namespace(s) used in the deployment/service.
```
Target cluster 'https://35.247.3.14' (nodes: demo-default-pool-0f8526ab-rb7b, 2+)

Apps in namespace 'kapp-demo'

Name              Namespaces             Lcs    Lca
spring-petclinic  spring-petclinic       false  22h

Lcs: Last Change Successful
Lca: Last Change Age

1 apps
```
If we didn’t have kapp and wanted to see all of the resources for this application, we could try running kubectl -n spring-petclinic get all. But there are a few issues here. First, get all doesn’t actually get all resource types. Second, we might have multiple applications running in this namespace. We would need something like a label to be able to filter on. kapp does this for you. Let’s take a look at the deployment and service.
```
kubectl -n spring-petclinic get deployment,service spring-petclinic --show-labels
```
To see all of the resources kapp created for the app, we use kapp inspect:
```
kapp -n kapp-demo inspect -a spring-petclinic
```
We can also look at logs, which is especially useful if something fails after the pods are up. kapp logs will show all pod logs in the app.
```
kapp -n kapp-demo logs -a spring-petclinic
```

Update App

Well, now we want to make it so we can share our app with other people without them needing to be in the cluster.

Let’s make a change to the YAML file and try running it again.

To reach the service externally, we can change the service type from itClusterIP to type LoadBalancer in kapp-spring-petclinic.yaml.

And then let’s run our kapp command again, but with -c to see a diff of the changes.

kapp deploy -n kapp-demo -a spring-petclinic -c -f kapp-spring-petclinic.yaml

This time our output should look like this where we see the change is that the service is being updated.

Target cluster 'https://35.247.3.14' (nodes: demo-default-pool-0f8526ab-rb7b, 2+)

@@ update service/spring-petclinic (v1) namespace: spring-petclinic @@
  ...
53, 53       kapp.k14s.io/app: "1627000710481082000"
54     -   type: ClusterIP
    54 +   type: LoadBalancer
55, 55   status:
56, 56     loadBalancer: {}

Changes

Namespace         Name              Kind     Conds.  Age  Op      Op st.  Wait to    Rs  Ri
spring-petclinic  spring-petclinic  Service  -       3h   update  -       reconcile  ok  -

Op:      0 create, 0 delete, 1 update, 0 noop
Wait to: 1 reconcile, 0 delete, 0 noop

Now if we run kubectl get, we should see an EXTERNAL_IP for the service.
```
kubectl -n spring-petclinic get svc
```
You can use curl, or you can open that IP in your browser which will look like the following:

Congrats, you did it!

To see what else you can do, run the following or go to the docs.
```
kapp -h
```

Cleanup

Now, if you want, you can delete what was created in this guide.

To delete the app you can run the following command. Make sure it is wanting to only delete what you are trying to delete before agreeing.

kapp delete -n kapp-demo -a spring-petclinic

Mine looks like the following:

Target cluster 'https://35.247.3.14' (nodes: demo-default-pool-0f8526ab-rb7b, 2+)

Changes

Namespace         Name                               Kind        Conds.  Age  Op      Op st.  Wait to  Rs  Ri
(cluster)         spring-petclinic                   Namespace   -       3h   delete  -       delete   ok  -
spring-petclinic  spring-petclinic                   Deployment  2/2 t   3h   delete  -       delete   ok  -
^                 spring-petclinic                   Endpoints   -       3h   -       -       delete   ok  -
^                 spring-petclinic                   Service     -       3h   delete  -       delete   ok  -
^                 spring-petclinic-7bbb794698        ReplicaSet  -       3h   -       -       delete   ok  -
^                 spring-petclinic-7bbb794698-h89vr  Pod         4/4 t   3h   -       -       delete   ok  -
^                 spring-petclinic-7bbb794698-x4gbk  Pod         4/4 t   3h   -       -       delete   ok  -

Op:      0 create, 3 delete, 0 update, 4 noop
Wait to: 0 reconcile, 7 delete, 0 noop

Delete namespace:
```
kubectl delete namespace kapp-demo
```

Learn More

To learn more, here are some resources:

On This Page

Getting Started with kapp

Tiffany Jernigan

Prerequisites

Deploy App

First Run

Looking At the App with kapp

Update App

Cleanup

Learn More