Should Kubernetes have a DSL for configuration?

Slides used for the introduction to my Birds of a Feather session at KubeCon EU in Berlin. A discussion of various approaches to using programming languages to configure Kubernetes rather than writing the raw data.

Transcript

1. (without introducing more risk) Should Kubernetes have a DSL? Puppet Gareth Rushgrove Alternative configuration options for K8
2. (without introducing more risk) @garethr
3. (without introducing more risk) Gareth Rushgrove
4. (without introducing more risk) What we’ll cover This session
5. - Setting the scene - Open discussion - Summary Gareth Rushgrove
6. (without introducing more risk) The argument Why not (only) YAML
7. Gareth Rushgrove Brian Grant, Google, Kubernetes Config SIG “We've had a few complaints that YAML is ugly, error prone, hard to read, etc. Are there any other alternatives we might want to support?
8. Gareth Rushgrove
9. (without introducing more risk) Gareth Rushgrove API wire format as user interface template: metadata: labels: app: guestbook tier: frontend spec: containers: - name: php-redis image: gcr.io/google_samples/gb-frontend:v4 resources: requests: cpu: 100m memory: 100Mi env:
10. The language to represent the data should be a simple, data-only format such as JSON or YAML, and programmatic modification of this data should be done in a real programming language Gareth Rushgrove Borg, Omega, and Kubernetes, ACM Queue, Volume 14, issue 1 http://queue.acm.org/detail.cfm?id=2898444 “
11. The reality is probably closer to most people hand writing YAML files Gareth Rushgrove
12. Code allows us to - Avoid repetition - Combine external inputs - Enforce correctness - Introduce abstractions Gareth Rushgrove
13. (without introducing more risk) Configuration language for JSON data Jsonnet
14. (without introducing more risk) jsonnet.org
15. (without introducing more risk) kubernetes examples
16. (without introducing more risk) kubecfg
17. (without introducing more risk) Gareth Rushgrove Jsonnet template $ cat squid.jsonnet local squid = { namespace:: "squid", squid_service: kube.Service("proxy") { metadata+: { namespace: $.namespace }, target_pod: $.squid.spec.template, port: 80, }, squid_data: kube.PersistentVolumeClaim("proxy") { metadata+: { namespace: $.namespace },
18. (without introducing more risk) A REPL for Kubernetes Kubeplay
19. (without introducing more risk) errordeveloper/kubeplay
20. (without introducing more risk) Gareth Rushgrove A REPL for Kubernetes $ ./kubeplay kubeplay (namespace="*")> pods # list pods in the cluster <list-of-pods> kubeplay (namespace="*")> @pod = _.any # pick a random pod from the list kubeplay (namespace="*")> puts @pod.to_json # output the pod definition { "metadata": { ... }, "spec": { ... "containers": [ {
21. (without introducing more risk) Gareth Rushgrove Ruby based DSL @metadata = replicasets("*/").to_ruby.items.map do |k,v| v.metadata end @metadata.each do |i| puts "Name:\t#{i.name}" puts "Labels:\t#{i.labels}" puts end
22. (without introducing more risk) Declarative Domain Specific Language Puppet
23. (without introducing more risk) garethr/garethr-kubernetes
24. (without introducing more risk) Gareth Rushgrove Puppet DSL kubernetes_pod { 'sample-pod': ensure => present, metadata => { namespace => 'default', }, spec => { containers => [{ name => 'container-name', image => 'nginx', }] }, }
25. (without introducing more risk) More Domain Specific Language Terraform
26. (without introducing more risk) maxmanuylov/terraform-provider-kubernetes
27. (without introducing more risk) Gareth Rushgrove Terraform provider resource "kubernetes_resource" "mypod" { # Required, must link on the corresponding "kubernetes_cluster" data s cluster = "${data.kubernetes_cluster.main.cluster}" collection = "pods" name = "mypod" labels { a = "b" } }
28. (without introducing more risk) A compiled typed JVM language for config Kotlin DSL
29. (without introducing more risk) k8-kotlin-dsl
30. (without introducing more risk) Gareth Rushgrove Ingress in Kotlin import com.fkorotkov.kubernetes.* import io.fabric8.kubernetes.api.model.IntOrString import io.fabric8.kubernetes.client.DefaultKubernetesClient fun main(args: Array<String>) { val client = DefaultKubernetesClient().inNamespace("default") client.extensions().ingresses().createOrReplace( ingress { metadata { name = "example-ingress" } spec { backend {
31. (without introducing more risk) A scala language for kubernetes config Skuber
32. (without introducing more risk) Skuber
33. (without introducing more risk) Gareth Rushgrove RC in Scala import skuber._ import skuber.json.format._ val nginxSelector = Map("app" -> "nginx") val nginxContainer = Container("nginx",image="nginx").exposePort(80) val nginxController= ReplicationController("nginx",nginxContainer,nginxSelector) .withReplicas(5) val nginxService = Service("nginx") .withSelector(nginxSelector) .exposeOnNodePort(30001 -> 80) import scala.concurrent.ExecutionContext.Implicits.global
34. (without introducing more risk) Useful parts of potential solutions Notable mentions
35. (without introducing more risk) JSON Schema
36. (without introducing more risk) Open API/Swagger
37. (without introducing more risk) Discussion And thanks for listening