tutorial.md

kpack Tutorial

This tutorial will walk through creating a kpack builder resource and a image resource to build a docker image from source and allow kpack rebuild the image with updates.

Prerequisites

1. kpack is installed and available on a kubernetes cluster

   Follow these docs to install and setup kpack

2. kpack cli

   Get the kp cli from the github release

Tutorial

1. Create a secret with push credentials for the docker registry that you plan on publishing OCI images to with kpack.

   The easiest way to do that is with kubectl create secret docker-registry

   kubectl create secret docker-registry tutorial-registry-credentials \
       --docker-username=user \
       --docker-password=password \
       --docker-server=string \
       --namespace default

   Note: The docker server must be the registry prefix for its corresponding registry. For dockerhub this should be https://index.docker.io/v1/. For GCR this should be gcr.io. If you use GCR then the username can be _json_key and the password can be the JSON credentials you get from the GCP UI (under IAM -> Service Accounts create an account or edit an existing one and create a key with type JSON).

   Your secret create should look something like this:

   kubectl create secret docker-registry tutorial-registry-credentials \
       --docker-username=my-dockerhub-username \
       --docker-password=my-dockerhub-password \
       --docker-server=https://index.docker.io/v1/ \
       --namespace default

   Note: Learn more about kpack secrets with the kpack secret documentation

2. Create a service account that references the registry secret created above

   apiVersion: v1
   kind: ServiceAccount
   metadata:
     name: tutorial-service-account
     namespace: default
   secrets:
   - name: tutorial-registry-credentials
   imagePullSecrets:
   - name: tutorial-registry-credentials

   Apply that service account to the cluster

   kubectl apply -f service-account.yaml

3. Create a cluster store configuration

   A store resource is a repository of buildpacks packaged in buildpackages that can be used by kpack to build OCI images. Later in this tutorial you will reference this store in a Builder configuration.

   We recommend starting with buildpacks from the paketo project. The example below pulls in java and nodejs buildpacks from the paketo project.

   apiVersion: kpack.io/v1alpha2
   kind: ClusterStore
   metadata:
     name: default
   spec:
     sources:
     - image: gcr.io/paketo-buildpacks/java
     - image: gcr.io/paketo-buildpacks/nodejs

   Apply this store to the cluster

   kubectl apply -f store.yaml

   Note: Buildpacks are packaged and distributed as buildpackages which are docker images available on a docker registry. Buildpackages for other languages are available from paketo.

4. Create a cluster stack configuration

   A stack resource is the specification for a cloud native buildpacks stack used during build and in the resulting app image.

   We recommend starting with the paketo base stack as shown below:

   apiVersion: kpack.io/v1alpha2
   kind: ClusterStack
   metadata:
     name: base
   spec:
     id: "io.buildpacks.stacks.jammy"
     buildImage:
       image: "paketobuildpacks/build-jammy-base"
     runImage:
       image: "paketobuildpacks/run-jammy-base"

   Apply this stack to the cluster

   kubectl apply -f stack.yaml

5. Create a Builder configuration

   A Builder is the kpack configuration for a builder image that includes the stack and buildpacks needed to build an OCI image from your app source code.

   The Builder configuration will write to the registry with the secret configured in step one and will reference the stack and store created in step three and four. The builder order will determine the order in which buildpacks are used in the builder.

   apiVersion: kpack.io/v1alpha2
   kind: Builder
   metadata:
     name: my-builder
     namespace: default
   spec:
     serviceAccountName: tutorial-service-account
     tag: <DOCKER-IMAGE-TAG>
     stack:
       name: base
       kind: ClusterStack
     store:
       name: default
       kind: ClusterStore
     order:
     - group:
       - id: paketo-buildpacks/java
     - group:
       - id: paketo-buildpacks/nodejs

   • Replace <DOCKER-IMAGE-TAG> with a valid image tag that exists in the registry you configured with the --docker-server flag when creating a Secret in step #1. The tag should be something like: your-name/builder or gcr.io/your-project/builder

   Apply this builder to the cluster

   kubectl apply -f builder.yaml

6. Apply a kpack image resource

   An image resource is the specification for an OCI image that kpack should build and manage.

   We will create a sample image resource that builds with the builder created in step five.

   The example included here utilizes the Spring Pet Clinic sample app. We encourage you to substitute it with your own application.

   Create an image resource:

   apiVersion: kpack.io/v1alpha2
   kind: Image
   metadata:
     name: tutorial-image
     namespace: default
   spec:
     tag: <DOCKER-IMAGE-TAG>
     serviceAccountName: tutorial-service-account
     builder:
       name: my-builder
       kind: Builder
     source:
       git:
         url: https://github.com/spring-projects/spring-petclinic
         revision: 3be289517d320a47bb8f359acc1d1daf0829ed0b

   • Replace <DOCKER-IMAGE-TAG> with a valid image tag that exists in the registry you configured with the --docker-server flag when creating a Secret in step #1. Something like: your-name/app or gcr.io/your-project/app
   • If you are using your application source, replace source.git.url & source.git.revision.

   Note: To use a private git repo follow the instructions in secrets

   Apply that image resource to the cluster

   kubectl apply -f image.yaml

   You can now check the status of the image resource.

   kubectl -n default get images

   You should see that the image resource has an unknown READY status as it is currently building.

    NAME                  LATESTIMAGE   READY
    tutorial-image                      Unknown
   

   You can tail the logs for image that is currently building using the kp cli

   kp build logs tutorial-image -n default
   

   Once the image resource finishes building you can get the fully resolved built OCI image with kubectl get

   kubectl -n default get image tutorial-image
   

   The output should look something like this:

   NAMESPACE   NAME                  LATESTIMAGE                                        READY
   default     tutorial-image        index.docker.io/your-project/app@sha256:6744b...   True
   

   The latest OCI image is available to be used locally via docker pull and in a kubernetes deployment.

7. Run the built app locally

   Download the latest OCI image available in step #6 and run it with docker.

   docker run -p 8080:8080 <latest-image-with-digest>

   You should see the java app start up:

       
              |\      _,,,--,,_
             /,`.-'`'   ._  \-;;,_
    _______ __|,4-  ) )_   .;.(__`'-'__     ___ __    _ ___ _______
    |       | '---''(_/._)-'(_\_)   |   |   |   |  |  | |   |       |
    |    _  |    ___|_     _|       |   |   |   |   |_| |   |       | __ _ _
    |   |_| |   |___  |   | |       |   |   |   |       |   |       | \ \ \ \
    |    ___|    ___| |   | |      _|   |___|   |  _    |   |      _|  \ \ \ \
    |   |   |   |___  |   | |     |_|       |   | | |   |   |     |_    ) ) ) )
    |___|   |_______| |___| |_______|_______|___|_|  |__|___|_______|  / / / /
    ==================================================================/_/_/_/
    
    :: Built with Spring Boot :: 2.2.2.RELEASE
   

8. kpack rebuilds

   We recommend updating the kpack image resource with a CI/CD tool when new commits are ready to be built.

   Note: You can also provide a branch or tag as the spec.git.revision and kpack will poll and rebuild on updates!

   We can simulate an update from a CI/CD tool by updating the spec.git.revision on the image resource used in step #6.

   If you are using your own application please push an updated commit and use the new commit sha. If you are using Spring Pet Clinic you can update the revision to: 4e1f87407d80cdb4a5a293de89d62034fdcbb847.

   Edit the image resource with:

   kubectl -n default edit image tutorial-image 
   

   You should see kpack schedule a new build by running:

   kubectl -n default get builds
   

   You should see a new build with

   NAME                                IMAGE                                          SUCCEEDED
   tutorial-image-build-1-8mqkc       index.docker.io/your-name/app@sha256:6744b...   True
   tutorial-image-build-2-xsf2l                                                       Unknown
   

   You can tail the logs for the image with the kp cli used in step #6.

   kp build logs tutorial-image -n default -b 2
   

   Note: This second build should be notably faster because the buildpacks are able to leverage the cache from the previous build.

9. Next steps

   The next time new buildpacks are added to the store, kpack will automatically rebuild the builder. If the updated buildpacks were used by the tutorial image resource, kpack will automatically create a new build to rebuild your OCI image.

   Now you can configure kpack to sign your images with cosign with the instructions in kpack with Cosign Tutorial.