mirror of
https://github.com/k3s-io/kubernetes.git
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chore(*): update election example (#82821)
* feat(*): simplify leader election example * chore(*): fix with comment * chore(*): add os.exit * chore(*): fix typo
This commit is contained in:
Mengjiang Bao
Kubernetes Prow Robot
parent
f985367ba4
commit
1185012da6
@ -23,7 +23,7 @@ go_library(
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"//staging/src/k8s.io/client-go/tools/clientcmd:go_default_library",
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"//staging/src/k8s.io/client-go/tools/leaderelection:go_default_library",
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"//staging/src/k8s.io/client-go/tools/leaderelection/resourcelock:go_default_library",
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"//staging/src/k8s.io/client-go/transport:go_default_library",
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"//vendor/github.com/google/uuid:go_default_library",
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"//vendor/k8s.io/klog:go_default_library",
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],
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)
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@ -7,15 +7,16 @@ This example demonstrates how to use the leader election package.
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Run the following three commands in separate terminals. Each terminal needs a unique `id`.
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```bash
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# first terminal
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go run *.go -kubeconfig=/my/config -logtostderr=true -id=1
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# first terminal
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go run main.go -kubeconfig=/path/to/kubeconfig -logtostderr=true -lease-lock-name=example -lease-lock-namespace=default -id=1
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# second terminal
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go run *.go -kubeconfig=/my/config -logtostderr=true -id=2
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# second terminal
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go run main.go -kubeconfig=/path/to/kubeconfig -logtostderr=true -lease-lock-name=example -lease-lock-namespace=default -id=2
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# third terminal
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go run *.go -kubeconfig=/my/config -logtostderr=true -id=3
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go run main.go -kubeconfig=/path/to/kubeconfig -logtostderr=true -lease-lock-name=example -lease-lock-namespace=default -id=3
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```
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> You can ignore the `-kubeconfig` flag if you are running these commands in the Kubernetes cluster.
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Now kill the existing leader. You will see from the terminal outputs that one of the remaining two processes will be elected as the new leader.
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@ -19,21 +19,18 @@ package main
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import (
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"context"
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"flag"
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"fmt"
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"log"
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"os"
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"os/signal"
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"strings"
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"syscall"
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"time"
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"github.com/google/uuid"
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metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
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clientset "k8s.io/client-go/kubernetes"
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"k8s.io/client-go/rest"
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"k8s.io/client-go/tools/clientcmd"
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"k8s.io/client-go/tools/leaderelection"
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"k8s.io/client-go/tools/leaderelection/resourcelock"
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"k8s.io/client-go/transport"
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"k8s.io/klog"
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)
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@ -62,13 +59,16 @@ func main() {
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var id string
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flag.StringVar(&kubeconfig, "kubeconfig", "", "absolute path to the kubeconfig file")
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flag.StringVar(&id, "id", "", "the holder identity name")
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flag.StringVar(&leaseLockName, "lease-lock-name", "example", "the lease lock resource name")
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flag.StringVar(&leaseLockNamespace, "lease-lock-namespace", "default", "the lease lock resource namespace")
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flag.StringVar(&id, "id", uuid.New().String(), "the holder identity name")
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flag.StringVar(&leaseLockName, "lease-lock-name", "", "the lease lock resource name")
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flag.StringVar(&leaseLockNamespace, "lease-lock-namespace", "", "the lease lock resource namespace")
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flag.Parse()
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if id == "" {
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klog.Fatal("unable to get id (missing id flag).")
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if leaseLockName == "" {
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klog.Fatal("unable to get lease lock resource name (missing lease-lock-name flag).")
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}
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if leaseLockNamespace == "" {
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klog.Fatal("unable to get lease lock resource namespace (missing lease-lock-namespace flag).")
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}
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// leader election uses the Kubernetes API by writing to a
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@ -82,6 +82,29 @@ func main() {
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}
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client := clientset.NewForConfigOrDie(config)
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run := func(ctx context.Context) {
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// complete your controller loop here
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klog.Info("Controller loop...")
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select {}
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}
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// use a Go context so we can tell the leaderelection code when we
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// want to step down
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ctx, cancel := context.WithCancel(context.Background())
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defer cancel()
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// listen for interrupts or the Linux SIGTERM signal and cancel
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// our context, which the leader election code will observe and
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// step down
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ch := make(chan os.Signal, 1)
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signal.Notify(ch, os.Interrupt, syscall.SIGTERM)
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go func() {
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<-ch
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klog.Info("Received termination, signaling shutdown")
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cancel()
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}()
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// we use the Lease lock type since edits to Leases are less common
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// and fewer objects in the cluster watch "all Leases".
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lock := &resourcelock.LeaseLock{
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@ -95,25 +118,6 @@ func main() {
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},
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}
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// use a Go context so we can tell the leaderelection code when we
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// want to step down
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ctx, cancel := context.WithCancel(context.Background())
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defer cancel()
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// use a client that will stop allowing new requests once the context ends
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config.Wrap(transport.ContextCanceller(ctx, fmt.Errorf("the leader is shutting down")))
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// listen for interrupts or the Linux SIGTERM signal and cancel
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// our context, which the leader election code will observe and
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// step down
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ch := make(chan os.Signal, 1)
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signal.Notify(ch, os.Interrupt, syscall.SIGTERM)
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go func() {
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<-ch
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log.Printf("Received termination, signaling shutdown")
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cancel()
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}()
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// start the leader election code loop
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leaderelection.RunOrDie(ctx, leaderelection.LeaderElectionConfig{
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Lock: lock,
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@ -131,12 +135,12 @@ func main() {
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OnStartedLeading: func(ctx context.Context) {
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// we're notified when we start - this is where you would
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// usually put your code
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klog.Infof("%s: leading", id)
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run(ctx)
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},
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OnStoppedLeading: func() {
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// we can do cleanup here, or after the RunOrDie method
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// returns
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klog.Infof("%s: lost", id)
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// we can do cleanup here
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klog.Infof("leader lost: %s", id)
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os.Exit(0)
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},
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OnNewLeader: func(identity string) {
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// we're notified when new leader elected
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@ -144,18 +148,8 @@ func main() {
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// I just got the lock
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return
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}
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klog.Infof("new leader elected: %v", identity)
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klog.Infof("new leader elected: %s", identity)
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},
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},
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})
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// because the context is closed, the client should report errors
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_, err = client.CoordinationV1().Leases(leaseLockNamespace).Get(leaseLockName, metav1.GetOptions{})
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if err == nil || !strings.Contains(err.Error(), "the leader is shutting down") {
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log.Fatalf("%s: expected to get an error when trying to make a client call: %v", id, err)
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}
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// we no longer hold the lease, so perform any cleanup and then
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// exit
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log.Printf("%s: done", id)
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}
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@ -14,6 +14,7 @@ require (
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github.com/golang/groupcache v0.0.0-20160516000752-02826c3e7903
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github.com/golang/protobuf v1.3.1
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github.com/google/gofuzz v1.0.0
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github.com/google/uuid v1.1.1
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github.com/googleapis/gnostic v0.0.0-20170729233727-0c5108395e2d
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github.com/gophercloud/gophercloud v0.1.0
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github.com/gregjones/httpcache v0.0.0-20170728041850-787624de3eb7
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1
staging/src/k8s.io/client-go/go.sum
generated
1
staging/src/k8s.io/client-go/go.sum
generated
@ -64,6 +64,7 @@ github.com/google/gofuzz v1.0.0 h1:A8PeW59pxE9IoFRqBp37U+mSNaQoZ46F1f0f863XSXw=
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github.com/google/gofuzz v1.0.0/go.mod h1:dBl0BpW6vV/+mYPU4Po3pmUjxk6FQPldtuIdl/M65Eg=
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github.com/google/martian v2.1.0+incompatible/go.mod h1:9I4somxYTbIHy5NJKHRl3wXiIaQGbYVAs8BPL6v8lEs=
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github.com/google/pprof v0.0.0-20181206194817-3ea8567a2e57/go.mod h1:zfwlbNMJ+OItoe0UupaVj+oy1omPYYDuagoSzA8v9mc=
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github.com/google/uuid v1.1.1 h1:Gkbcsh/GbpXz7lPftLA3P6TYMwjCLYm83jiFQZF/3gY=
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github.com/google/uuid v1.1.1/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
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github.com/googleapis/gax-go/v2 v2.0.4/go.mod h1:0Wqv26UfaUD9n4G6kQubkQ+KchISgw+vpHVxEJEs9eg=
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github.com/googleapis/gnostic v0.0.0-20170729233727-0c5108395e2d h1:7XGaL1e6bYS1yIonGp9761ExpPPV1ui0SAC59Yube9k=
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