Overview
根據Kuberneter文件對Controller的描述，Controller在kubernetes中是負責協調的元件，根據設計模式可知，controller會不斷的你的物件（如Pod）從當前狀態與期望狀態同步的一個過程。當然Controller會監聽你的實際狀態與期望狀態。
Writing Controllers
package main
import (
"flag"
"fmt"
"os"
"time"
v1 "k8s.io/api/core/v1"
"k8s.io/apimachinery/pkg/fields"
utilruntime "k8s.io/apimachinery/pkg/util/runtime"
"k8s.io/apimachinery/pkg/util/wait"
"k8s.io/client-go/kubernetes"
"k8s.io/client-go/rest"
"k8s.io/client-go/tools/cache"
"k8s.io/client-go/tools/clientcmd"
"k8s.io/client-go/util/homedir"
"k8s.io/client-go/util/workqueue"
"k8s.io/klog"
)
type Controller struct {
lister cache.Indexer
controller cache.Controller
queue workqueue.RateLimitingInterface
}
func NewController(lister cache.Indexer, controller cache.Controller, queue workqueue.RateLimitingInterface) *Controller {
return &Controller{
lister: lister,
controller: controller,
queue: queue,
}
}
func (c *Controller) processItem() bool {
item, quit := c.queue.Get()
if quit {
return false
}
defer c.queue.Done(item)
fmt.Println(item)
err := c.processWrapper(item.(string))
if err != nil {
c.handleError(item.(string))
}
return true
}
func (c *Controller) handleError(key string) {
if c.queue.NumRequeues(key) < 3 {
c.queue.AddRateLimited(key)
return
}
c.queue.Forget(key)
klog.Infof("Drop Object %s in queue", key)
}
func (c *Controller) processWrapper(key string) error {
item, exists, err := c.lister.GetByKey(key)
if err != nil {
klog.Error(err)
return err
}
if !exists {
klog.Info(fmt.Sprintf("item %v not exists in cache.\n", item))
} else {
fmt.Println(item.(*v1.Pod).GetName())
}
return err
}
func (c *Controller) Run(threadiness int, stopCh chan struct{}) {
defer utilruntime.HandleCrash()
defer c.queue.ShutDown()
klog.Infof("Starting custom controller")
go c.controller.Run(stopCh)
if !cache.WaitForCacheSync(stopCh, c.controller.HasSynced) {
utilruntime.HandleError(fmt.Errorf("sync failed."))
return
}
for i := 0; i < threadiness; i++ {
go wait.Until(func() {
for c.processItem() {
}
}, time.Second, stopCh)
}
<-stopCh
klog.Info("Stopping custom controller")
}
func main() {
var (
k8sconfig *string //使用kubeconfig配置檔案進行叢集許可權認證
restConfig *rest.Config
err error
)
if home := homedir.HomeDir(); home != "" {
k8sconfig = flag.String("kubeconfig", fmt.Sprintf("%s/.kube/config", home), "kubernetes auth config")
}
k8sconfig = k8sconfig
flag.Parse()
if _, err := os.Stat(*k8sconfig); err != nil {
panic(err)
}
if restConfig, err = rest.InClusterConfig(); err != nil {
// 這裡是從masterUrl 或者 kubeconfig傳入叢集的資訊，兩者選一
restConfig, err = clientcmd.BuildConfigFromFlags("", *k8sconfig)
if err != nil {
panic(err)
}
}
restset, err := kubernetes.NewForConfig(restConfig)
lister := cache.NewListWatchFromClient(restset.CoreV1().RESTClient(), "pods", "default", fields.Everything())
queue := workqueue.NewRateLimitingQueue(workqueue.DefaultControllerRateLimiter())
indexer, controller := cache.NewIndexerInformer(lister, &v1.Pod{}, 0, cache.ResourceEventHandlerFuncs{
AddFunc: func(obj interface{}) {
fmt.Println("add ", obj.(*v1.Pod).GetName())
key, err := cache.MetaNamespaceKeyFunc(obj)
if err == nil {
queue.Add(key)
}
},
UpdateFunc: func(oldObj, newObj interface{}) {
fmt.Println("update", newObj.(*v1.Pod).GetName())
if newObj.(*v1.Pod).Status.Conditions[0].Status == "True" {
fmt.Println("update: the Initialized Status", newObj.(*v1.Pod).Status.Conditions[0].Status)
} else {
fmt.Println("update: the Initialized Status ", newObj.(*v1.Pod).Status.Conditions[0].Status)
fmt.Println("update: the Initialized Reason ", newObj.(*v1.Pod).Status.Conditions[0].Reason)
}
if len(newObj.(*v1.Pod).Status.Conditions) > 1 {
if newObj.(*v1.Pod).Status.Conditions[1].Status == "True" {
fmt.Println("update: the Ready Status", newObj.(*v1.Pod).Status.Conditions[1].Status)
} else {
fmt.Println("update: the Ready Status ", newObj.(*v1.Pod).Status.Conditions[1].Status)
fmt.Println("update: the Ready Reason ", newObj.(*v1.Pod).Status.Conditions[1].Reason)
}
if newObj.(*v1.Pod).Status.Conditions[2].Status == "True" {
fmt.Println("update: the PodCondition Status", newObj.(*v1.Pod).Status.Conditions[2].Status)
} else {
fmt.Println("update: the PodCondition Status ", newObj.(*v1.Pod).Status.Conditions[2].Status)
fmt.Println("update: the PodCondition Reason ", newObj.(*v1.Pod).Status.Conditions[2].Reason)
}
if newObj.(*v1.Pod).Status.Conditions[3].Status == "True" {
fmt.Println("update: the PodScheduled Status", newObj.(*v1.Pod).Status.Conditions[3].Status)
} else {
fmt.Println("update: the PodScheduled Status ", newObj.(*v1.Pod).Status.Conditions[3].Status)
fmt.Println("update: the PodScheduled Reason ", newObj.(*v1.Pod).Status.Conditions[3].Reason)
}
}
},
DeleteFunc: func(obj interface{}) {
fmt.Println("delete ", obj.(*v1.Pod).GetName(), "Status ", obj.(*v1.Pod).Status.Phase)
// 上面是事件函式的處理，下面是對workqueue的操作
key, err := cache.MetaNamespaceKeyFunc(obj)
if err == nil {
queue.Add(key)
}
},
}, cache.Indexers{})
c := NewController(indexer, controller, queue)
stopCh := make(chan struct{})
stopCh1 := make(chan struct{})
c.Run(1, stopCh)
defer close(stopCh)
<-stopCh1
}
通過日誌可以看出，Pod create後的步驟大概為4步：
- Initialized：初始化好後狀態為Pending
- PodScheduled：然後排程
- PodCondition
- Ready
add netbox
default/netbox
netbox
update netbox status Pending to Pending
update: the Initialized Status True
update netbox status Pending to Pending
update: the Initialized Status True
update: the Ready Status False
update: the Ready Reason ContainersNotReady
update: the PodCondition Status False
update: the PodCondition Reason ContainersNotReady
update: the PodScheduled Status True
update netbox status Pending to Running
update: the Initialized Status True
update: the Ready Status True
update: the PodCondition Status True
update: the PodScheduled Status True
大致上與 kubectl describe pod 看到的內容頁相似
default-scheduler Successfully assigned default/netbox to master-machine
Normal Pulling 85s kubelet Pulling image "cylonchau/netbox"
Normal Pulled 30s kubelet Successfully pulled image "cylonchau/netbox"
Normal Created 30s kubelet Created container netbox
Normal Started 30s kubelet Started container netbox
Reference