Cloud Native Ambassador Day - Extending Kubernetes

Cloud Native Ambassador Day - Extending Kubernetes

Extending Kubernetes: Abstract: When somebody asks me why Kubernetes got so much traction the answer is always the same: “its extendibility”. You can run it everywhere, almost all cloud providers or bare metal providers can deliver a managed or integrated distribution of Kubernetes. This is because it acts as a pluggable API gateway to manage your infrastructure across providers. As a developer or infrastructure operator having the ability to write the best integration your company or team needs is a huge plus. During this talk, Gianluca will show you the different integration points you can use to extend Kubernetes such as shared informers, controller, kubectl plugin. Concepts are generically applicable to Kubernetes, code will mainly be in Go.


Gianluca Arbezzano

October 14, 2020


  1. Extending Kubernetes The superpower behind the Kubernetes API Gianluca Arbezzano

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  2. apiVersion: batch/v1 kind: Job metadata: name: hello spec: template: #

    This is the pod template spec: containers: - name: hello image: busybox command: ['sh', '-c', 'echo "Hello, Kubernetes!" && sleep 3600'] restartPolicy: OnFailure # The pod template ends here Example coming from Gianluca Arbezzano - -
  3. Kubernetes is a declarative framework If you use it just

    as end tool you are missing its real value
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  5. k-proxy kubelet sched sched sched Control Plane Node etcd Kubernetes

    cluster api api api c-c-m c-c-m c-c-m c-m c-m c-m Node Node k-proxy kubelet kubelet k-proxy Control plane Scheduler sched Cloud controller manager (optional) c-c-m Controller manager c-m kubelet kubelet kube-proxy k-proxy (persistence store) etcd etcd Node API server api from Gianluca Arbezzano - -
  6. from SlideShare: Moby CRI Containerd Gianluca Arbezzano - -
  7. How you justify Kubernetes Gianluca Arbezzano - -

  8. Play your own game. That's why services have their own

    API. Gianluca Arbezzano - -
  9. You know yourself, your team and your product. Build around

    your requirement Gianluca Arbezzano - -
  10. Who am I? Software Engineer at Equinix Metal (Packet) Open

    Source maintainer for Kubernetes, Docker, TestContainer Docker Captain and CNCF Ambassador When not coding I grow vegetables I am active on Twitter as @gianarb
  11. Kubernetes follows the same rule, if kubectl is not enough

    because you have an half way workflow that you like, or the kubectl makes your solution hard to maintain, it is OK to build something by yourself. Gianluca Arbezzano - -
  12. There different ways to extend Kubernetes, here a couple: .

    A kubectl plugin. . Via Client-GO or any other SDK. . Custom Resource Definition. . Aggregation layer Gianluca Arbezzano - -
  13. Let's start with kubectl . It is by far the

    most flexible and easy way to extend Kubernetes. You have to deliver an executable in your $PATH that starts with kubectl-* . Gianluca Arbezzano - -
  14. Examples: A binary called kubectl-ns can be executed as kubectl

    ns A binary called kubectl-profefe can be executed as kubectl profefe Gianluca Arbezzano - -
  15. kubectl-profefe Profefe is an open source project to do continuous

    profiling of application using pprof, such as Golang. cron job application runtime/pprof net/http/pprof pull Storage developer profefe-collector query push GET /debug/pprof/profile Gianluca Arbezzano - -
  16. I wrote a project called profefe/kube-profefe that acts as a

    bridge between profefe and Kubernetes. . It serves a binary called kprofefe , it can run as Kubernetes cronjob and it collects profiles targeting application running in Kubernetes. . kubectl-profefe helps you to interact with profefe and Kubernetes. Gianluca Arbezzano - -
  17. $ kubectl profefe --help It is a kubectl plugin that

    you can use to retrieve and manage profiles in Go. Available Commands: capture Capture gathers profiles for a pod or a set of them. If can filter by namespace and via label selector. get Display one or many resources help Help about any command load Load a profile you have locally to profefe Flags: -A, --all-namespaces If present, list the requested object(s) across all namespaces --as string Username to impersonate for the operation --as-group stringArray Group to impersonate for the operation, this flag can be repeated to specify multiple groups. --cluster string The name of the kubeconfig cluster to use --context string The name of the kubeconfig context to use -f, --filename strings identifying the resource. -h, --help help for kubectl-profefe --insecure-skip-tls-verify If true, the server's certificate will not be checked for validity. This will make your HTTPS connections insecure --kubeconfig string Path to the kubeconfig file to use for CLI requests. -n, --namespace string If present, the namespace scope for this CLI request -l, --selector string Selector (label query) to filter on, supports '=', '==', and '!='.(e.g. -l key1=value1,key2=value2) Use "kubectl-profefe [command] --help" for more information about a command. Gianluca Arbezzano - -
  18. Links about kubectl plugins: "My experience with Krew to manage

    kubectl plugins" "kubectl flags in your plugin" Gianluca Arbezzano - -
  19. Client GO and other SDKs Kubernetes API works as any

    other API. There are client libraries that you can use in many languages or it works via HTTP, and all the languages have an HTTP client available. Gianluca Arbezzano - -
  20. Not all the languages are the same There are official

    supported an unofficial libraries available out there. Go, Javascript, Haskell, Python, Java, Dotnet are supported by the Kubernetes community, you can check out the actual documentation. All of them are in different state, Golang is well done. Gianluca Arbezzano - -
  21. kprofefe the binary I told you about before uses the

    client-go library to do a couple of things: Retrieve pods filtered according to label section or/and per namespace in order to get the right targets for profefe It uses the annotations for a particular pod in order to figure out where the pprof server runs (the right port and path) Gianluca Arbezzano - -
  22. Get pods // GetSelectedPods returns all the pods with the

    profefe annotation enabled // filtered by the selected labels func GetSelectedPods(clientset kubernetes.Interface, namespace string, listOpt metav1.ListOptions) ([]v1.Pod, error) { target := []v1.Pod{} pods, err := clientset.CoreV1().Pods(namespace).List(listOpt) if err != nil { return target, err } for _, pod := range pods.Items { enabled, ok := pod.Annotations[ProfefeEnabledAnnotation] if ok && enabled == "true" && pod.Status.Phase == v1.PodRunning { target = append(target, pod) } } return target, nil } Gianluca Arbezzano - -
  23. Port forward programmatically func PortForwardAPod(req PortForwardAPodRequest) error { path :=

    fmt.Sprintf("/api/v1/namespaces/%s/pods/%s/portforward", req.Pod.Namespace, req.Pod.Name) hostIP := strings.TrimLeft(req.RestConfig.Host, "htps:/") transport, upgrader, err := spdy.RoundTripperFor(req.RestConfig) if err != nil { return err } dialer := spdy.NewDialer( upgrader, &http.Client{Transport: transport}, http.MethodPost, &url.URL{Scheme: "https", Path: path, Host: hostIP}) fw, err := portforward.New( dialer, []string{fmt.Sprintf("%d:%d", req.LocalPort, req.PodPort)}, req.StopCh, req.ReadyCh, req.Streams.Out, req.Streams.ErrOut) if err != nil { return err } return fw.ForwardPorts() } Repository: gianarb/kube-port-forward
  24. Custom Resource Definition (CRD) Terraform has the concept of modules.

    A Terraform module is a bridge between an external resource and Terraform. A CRD is the same, but with Kubernetes. Gianluca Arbezzano - -
  25. Custom Resource Definition (CRD) Native resources: Pod, Services, Deployment, StatefulSet,

    Ingress... Gianluca Arbezzano - -
  26. AWS Controllers for Kubernetes: Elastic Load Balancer, S3 bucket, CloudFormation

    Stack. Checkout: ACK Gianluca Arbezzano - -
  27. None
  28. client api-se kube crd-cont Gianluca Arbezzano - -

  29. Why you should write a CRD? Your team uses Kubernetes

    a lot, they know how to use the kubectl and client-go. You can make available for them external services like DNS management or a binary/image repository with an user experience they already know. Gianluca Arbezzano - -
  30. Kubernetes gives you a bunch of useful features that you

    can leverage: . Authentication . Authorization . Audit Logs . Event System . CLI (kubectl) and client libraries Gianluca Arbezzano - -
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  32. Thank you Any question? Reach out to me via Twitter

    @gianarb. Gianluca Arbezzano - -