ko-demo

ko is a build/publish/deploy tool for go applications on Kubernetes

It allows you to:

• build Go binaries
• containerize them and publish to a registry
• automatically update Kubernetes manifests to references the correct container image

Prerequisite

run then outside this project root and $GOPATH

# go lang  build/publish/deploy tool
go get -u github.com/google/ko/cmd/ko

Local

You can certainly build/run your code locally:

Run

go run main.go

Test

curl http://localhost:8080

Deploy

Configure a Registry

To specify the registry that you want to use, set the KO_DOCKER_REPO variable, for instance:

to publish locally set: export KO_DOCKER_REPO=ko.local

export PROJECT_ID=ngx-starter-kit
export KO_DOCKER_REPO=gcr.io/${PROJECT_ID}

Usage

Write a Kubernetes manifest with an import path that is similar to a Go import path like:

apiVersion: apps/v1beta1
kind: Deployment
metadata:
  name: hello-world
spec:
---
template:
---
spec:
  containers:
    - name: hello-world
      image: github.com/xmlking/ko-demo

Deploying

Then to start the build, containerize and deploy a single ko command is necessary.

ko apply -f deploy/

# -P or --preserve-import-paths
ko apply -P -f deploy/

# Deploy to minikube w/o registry.
ko apply -L -f deploy/

# This is the same as above.
KO_DOCKER_REPO=ko.local ko apply -f deploy/

To deploy in a different namespace:

ko -n nondefault apply -f deploy/

You will see a Pod running and you will be able to call your Go function:

kubectl get pods
NAME                                            READY     STATUS      RESTARTS   AGE
hello-world-59868cf5f9-5gqhj                    1/1       Running     0          5s

kubectl port-forward pod/hello-world-59868cf5f9-5gqhj 8080:8080 &
[1] 99038

curl localhost:8080
Handling connection for 8080
Hello world !

Teardown

ko delete -f deploy/

Build/publish but do not deploy

If all you want to do is build the Go binary and publish an image to the registry then, with the Demo project cloned in your $GOPATH.

ko publish github.com/xmlking/ko-demo
# publish to local docker repo
ko resolve -L -f deploy/

Release Management

ko is also useful to help manageing releases

# publish to  docker repo ar KO_DOCKER_REPO
ko resolve -P -f deploy/ > release.yaml
# publish to local docker repo
ko resolve -P -L -f deploy/ > release.yaml

This will publish all of the binary components as container images to gcr.io/xmlking/... and create a release.yaml file containing all of the configuration for your application with inlined image references.

This resulting configuration may then be installed onto Kubernetes clusters via:

kubectl apply -f release.yaml

Run Docker

docker run -it -p 8080:8080  ko.local/github.com/xmlking/ko-demo
# test
curl http://localhost:8080