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Should Kubernetes have a DSL for configuration?

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.


Gareth Rushgrove

March 30, 2017

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  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

  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

  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

  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