本文主要讲解kubernetes的client的深入了解，最佳实践等等。

kubernetes集群三步安装

How to access a kubernetes cluster

  • CLI: kubectl
  • UI: dashboard
  • Access rest api
    • kubectl proxy ; curl localhost:8001/api/v1/namespaces/pods
  • Programmatic access
    • client-go
    • other clients (open api)
      • java
      • python

Contents of client-go

  • Different client
    • clientset
      • config
        • out of cluster
          • kube-config
          • auth plugin(cloud)
        • in cluster
          • rest.InClusterConfig() (serviceaccount)
      • use:
        • clientset.Core(“namespace”).Pods().Create(pod)
    • dynamic client
    • restclient
  • writing controllers
    • workqueue
    • informer

Clients

Clientset

Get

get

go 
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type GetOptions struct {	
	// - if unset, then the result is returned from remote storage based on quorum-read flag;
	// - if it's 0, then we simply return what we currently have in cache, no guarantee;
	// - if set to non zero, then the result is at least as fresh as given rv.
	ResourceVersion string 	
}

List

list

  • ListOptions.ResourceVersion has the same meaning as GetOptions.ResourceVersion
  • Informer uses it

Watch

  • starts watching from opt.ResourceVersion
  • best practice: always set the ResourceVersion
  • api server will time out a watch 5-10 min
    go 
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    options :=api.ListOptions{ResourceVersion:"0"}
list,err :=r.listerWatcher.List(options)
resourceVersion = listMetaInterface.GetResourceVersion()
options = api.ListOptions{
   ResourceVersion : resourceVersion,
}
w,err :=r.listerWatcher.Watch(options)

Update && UpdateStatus

  • optimistic concurrency via cap (compare and swap)

Patch

  • merge
  • safe for unknown fields
  • retry 5 times at server
  • best practice: always set the origina uid in the patch
    • namespace+name is not unique across time

Delete

  • DeleteOptions.Preconditions
    • uid : namespace+name is not unique across time
  • DeleteOptions.PropagationPolicy
    • Orphan : not delete dependents resource,only delete current controller.
    • Background: delete current controller,other dependents resource gc delete.
    • Foreground: delete current controller must be delete dependents resource.

Dynamic client

  • example
    • ret,err:=client.Reource(resource,namespace).Get(name)
    • ret is of type map[string]interface{}
    • structured access to ObjectMet, e.g., ret.GetUID()
  • used extensively in pkg/controller/<namespace,garbagecontrollector>
  • crd
  • only support json, json < protobuf

RESTClient

  • example
    • var ret v1.Pod err:= c.rest.Get().Resource(“pods”).Namespace(namespace).Do().Into(&ret)
    • ret is typed
    • DoRaw() return byte[]
  • base of clientset and dynamic client
  • supports json and proto
  • need to satisfy the api machinery