Note: Skaffold now includes a ko builder. When you use the ko builder, you do not need to provide a custom build shell script or install the ko binary.

This example shows how the custom builder can be used to build artifacts with ko.

• building a single Go file app with ko
• tagging using the tagPolicy (sha256), to mimic the behavior of ko
• deploying a single container pod using kubectl

For this tutorial to work, you will need to have Skaffold and a Kubernetes cluster set up. To learn more about how to set up Skaffold and a Kubernetes cluster, see the getting started docs.

This tutorial will demonstrate how Skaffold can build a simple Hello World Go application with ko and deploy it to a Kubernetes cluster.

First, clone the Skaffold repo and navigate to the custom example for sample code:

git clone https://github.com/GoogleContainerTools/skaffold.git

cd skaffold/examples/custom

Take a look at the build.sh file, which uses ko to containerize source code:

#!/usr/bin/env bash
set -Eefuo pipefail

if ! [ -x "$(go env GOPATH)/bin/ko" ]; then
    pushd "$(mktemp -d)"
    curl -L https://github.com/ko-build/ko/archive/v0.13.0.tar.gz | tar --strip-components 1 -zx
    go build -o "$(go env GOPATH)"/bin/ko .
    popd
fi

output=$("$(go env GOPATH)"/bin/ko publish --local --preserve-import-paths --tags= . | tee)
ref=$(echo "$output" | tail -n1)

docker tag "$ref" "$IMAGE"
if [[ "${PUSH_IMAGE}" == "true" ]]; then
    echo "Pushing $IMAGE"
    docker push "$IMAGE"
else
    echo "Not pushing $IMAGE"
fi

and the skaffold config, which configures image ko://github.com/GoogleContainerTools/skaffold/examples/custom to build with build.sh:

apiVersion: skaffold/v4beta5
kind: Config
build:
  artifacts:
  - image: ko://github.com/googlecontainertools/skaffold/examples/custom
    custom:
      buildCommand: ./build.sh
      dependencies:
        paths:
        - "**/*.go"
        - go.*
        - .ko.yaml
  tagPolicy:
    sha256: {}

The k8s/pod.yaml manifest file uses the same image reference:

apiVersion: v1
kind: Pod
metadata:
  name: getting-started-custom
spec:
  containers:
  - name: getting-started-custom
    image: ko://github.com/googlecontainertools/skaffold/examples/custom

For more information about how this works, see the Skaffold custom builder documentation.

Now, use Skaffold to deploy this application to your Kubernetes cluster:

skaffold run --tail --default-repo <your repo>

With this command, Skaffold will build the github.com/googlecontainertools/skaffold/examples/custom artifact with ko and deploy the application to Kubernetes. You should be able to see Hello, World! printed every second in the Skaffold logs.

To clean up your Kubernetes cluster, run:

skaffold delete