k8s

Introduction

The library implements various handlers to more easier create/update/apply/patch/delete/get/list/watch k8s resources such as pods, deployments, etc, inside or outside k8s cluster. A program that uses the library and runs in a k8s pod meant to be inside k8s cluster. If you simply run examples in your pc/mac or server, it meant outside k8s cluster. Both of inside and outside k8s cluster are supported by the library.

There are three kind handler:

• k8s handler. Its a universal handler that simply invoke dynamic handler to create/update/patch/delete k8s resources and get/list k8s resources from listers instead of accessing the API server directly.
• dynamic handler. Its a universal handler that create/update/delete/patch/get/list k8s resources by the underlying dynamic client.
• typed handler such as deployment/pod handler. Its a typed handler that use typed client(clientset) to create/update/patch/delete/get/list typed resources(such as deployments, pods, etc.).

To create a handler for outside or inside cluster just call deployment.New(ctx, "", namespace). The New() function will find the kubeconfig file or the file pointed to by the variable KUBECONFIG. If neither is found, it will use the default kubeconfig filepath $HOME/.kube/config. New() will create a deployment handler for the outside cluster if kubeconfig is found . If no kubeconfig file is found, New() will create an in-cluster rest.Config to create the deployment handler.

The kubeconfig precedence is:

• kubeconfig variable passed.
• KUBECONFIG environment variable pointing at a file.
• $HOME/.kube/config if exists.
• In-cluster config if running in cluster.

The variable namespace is used to limit the scope of the handler. If namespace=test, the handler is only allowed to create/update/delete deployments in namespace/test. Of course, handler.WithNamespace(newNamespace) returns a new temporary handler that allowed to create/update/delete deployments in the new namespace, for examples:

namespace := "test"
newNamespace := "test-new"
// Inside cluster. the program run within k8s pod.
handler, _ := deployment.New(ctx, "", namespace)
// handler is only allowed to create/update/delete deployment in namespace/test.
handler.Create(filename)
// handler is only allowed to create/update/delete deployment in namespace/test-new.
handler.WithNamespace(newNamespace).Create(filename)
// handler is only allowed to create/update/delete deployment in namespace/test (not namespace/test-new).
handler.Create(filename)
handler.ResetNamespace(newNamespace)
// handler is only allowed to create/update/delete deployment in namespace/test-new (not namespace/test).
handler.Create(filename)

The namespace precedence is:

• namespace defined in yaml file or json file.

• namespace specified by WithNamespace() or MultiNamespace() method.

• namespace specified in New() or NewOrDie() funciton.

• namespace will be ignored if k8s resource is cluster scope.

• if namespace is empty, default to "default" namespace.

The library is used by another open source project that used to backup pv/pvc data attached by deployments/statefulsets/daemosnets/pods running in k8s cluster.

For furthermore examples of how to use this library, see examples.

Installation

go get github.com/forbearing/k8s@v0.12.4

Documents

k8s handler examples:

Its a universal handler that simply invoke dynamic handler to create/update/apply/patch/delete/watch k8s resources and get/list k8s resources from listers instead of accessing the API server directly.

• How to create k8s resources.
• How to update k8s resources.
• How to apply k8s resources.
• How to delete k8s resources.
• How to get k8s resources.
• How to list k8s resources.
• Howt to watch k8s resources.
• informer usage.

Dynamic handler examples:

Its a universal handler that create/update/apply/patch/delete/get/list/watch k8s resources by the underlying dynamic client.

• How to create k8s resources inside cluster or outside cluster.
• How to update k8s resources.
• How to apply k8s resources.
• How to patch k8s resource.
• How to delete k8s resources.
• How to get k8s resources.
• How to list k8s resources.
• How to watch a single k8s resources with specified kind.
• How to watch a single or multiple k8s resource with specified kind and selected by label.
• How to watch a single or multiple k8s resource with specified kind and selected by field.
• How to watch all k8s resources in the specified namespace.
• How to watch all k8s resources.
• dynamic informer usage.

Deployment handler examples:

Its a typed handler that use typed client(clientset) to create/update/apply/patch/delete/get/list/watch typed resources(such as deployments, pods, etc.).

• How to create deployment resources inside cluster or outside cluster.
• How to update deployment resources inside cluster or outside cluster.
• How to apply deployment resources.
• How to patch deployment resources.
• How to delete deployment resources.
• How to get deployment resources.
• How to list deployment resources.
• How to watch a single deployment resources.
• How to watch a single or multiple deployment resources selected by label.
• How to watch a single or multiple deployment resources selected by field.
• How to watch all deployment resources in the specified namespace.
• How to watch all deployment resources.
• How to change the number of deployment replicas.
• Deployment informer.
• More usage for informer.
• Deployment tools.
  • GetPods(): get all pods ownerd by a deployment
  • GetRS(): get all replicaset ownerd by a deployment
  • GetPVC()/GetPV(): Get PVC/PV mounted by a deployment
  • IsReady(): check if a deployment is ready/available/rollout update finished.
  • WaitReady(): block here until a deployment is ready/available/rollout update finished.

Pod handler examples:

• How to execute command within pod.
• How to port-forward a local port to pod.
• How to get pod logs

More examples:

• ApplyF()/DeleteF() apply/delete various k8s resource from a yaml file.
• Check whether the k8s resources has the specifed label, Get/Set/Remove labels of k8s resources
• Check whether the k8s resources has the specifed annotation, Get/Set/Remove labels of k8s annotations
• Find k8s resource's GroupVersionKind from yaml file, json file, bytes data, map[string]interface{}, etc.
• Find k8s resource's GroupVersionResources from yaml file, json file, bytes data, map[string]interface{}, etc.
• Check if the k8s resource is namespace scope from yaml file, json file, bytes data, map[string]interface{}, etc.

TODO

• https://github.com/kubernetes/kubectl/tree/master/pkg
• Simplify the use of client-go informer, lister
• create/delete/update/delete/get ... all kinds of k8s resources by dyanmic client.
• Support crate/update/delete/get... Event resources
• Support crate/update/delete/get... Endpoint resources
• Support crate/update/delete/get... EndpointSlice resources
• Support crate/update/delete/get... LimitRange resources
• Support crate/update/delete/get... PriorityClass resources
• Support crate/update/delete/get... ResourceQuota resources
• Support crate/update/delete/get... Lease resources
• Add variables: GVK, GVR, Kind, Group, Version, Resource.
• signal handler
• Finalizers
• controller and owner
• UpdateStatus: update Deployment/StatefulSet... status
• UpdateScale: scale Deployment/StatefulSet...
• DeleteCollection
• Leader Election
• Recoder
• Replace interface{} -> any
• fack client
• EnvTest
• healthz
• metrics
• port-forward for pod, deployment and service
• proxy
• all handler support Patch() method to patch k8s resource.
• operators refer to https://sdk.operatorframework.io/docs/building-operators/golang/references/client/
• Has/Get/GetAll/Set/Remove/RemoveAll Labels and Annotations
• Add MultiNamespace() method to create/update/delete k8s resource in multi namespaces at once.
• k8s handler create/update/delete/apply k8s resource by the underling dynamic but get/list from listers.
• create/update/delete/apply muitlple k8s resource at once.
• Admission Webhook: validating admission webhook, mutating admission webhook.
• AutoVersion() find appropriate resource version for your kubernetes cluster and return a dynamic.Handler to create/update/apply/patch/delete/get/list/watch current k8s object, for example: cronjob version is v1beta1 in k8s v1.19.x.
• ForVersion()
• Create()/Update()/Apply() support metav1.Object
• Typed handler and dynamc handler add function NewWithOptions() and NewWithOptionsOrDie() to create new Handler with custom options, such like QPS, Burst, RateLimter that defined in rest.Config, etc.