ko is a little unknown gem, lost in the GitHub maze.
ko is widely used in knative development but somehow very little advocacy has been done around this tool.
It allows you to:
- build Go binaries
- containerize them and publish to a registry
- automatically update Kubernetes manifests to references the correct container image
All of this in one single command.
With a working Go environment a simple go get will give you ko:
go get github.com/google/go-containerregistry/cmd/ko
To specify the registry that you want to use, set the KO_DOCKER_REPO variable, for instance:
export KO_DOCKER_REPO=gcr.io/triggermesh
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/sebgoa/kodemo/cmd/hello
Then to start the build, containerization and deployment a single ko command is necessary.
ko apply -f config/
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-54557f6647-wsng6 1/1 Running 0 50s
$ kubectl port-forward pod/hello-world-54557f6647-wsng6 8080:8080 &
[1] 99038
$ curl localhost:8080
Handling connection for 8080
Hello world !
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/sebgoa/kodemo/cmd/hello
If you want to get started with ko, you can try the kodemo repository is a simple demo project. It has the following structure:
$ tree
.
├── LICENSE
├── README.md
├── cmd
│ └── hello
│ └── hello.go
└── config
└── deploy.yaml
You can certainly build your code locally:
go build cmd/hello/hello.go