client-go/examples/create-update-delete-deployment/main.go
John Kelly ddf6c35ca5 client-go: use retry util in CRUD example
This updates the create-update-delete-deployment example with the following:
Make use of client-go retry util in Update() steps instead of simple for loops.
Using RetryOnConflict is generally better practice as it won't become stuck in a retry loop and uses exponential backoff to prevent exhausting the apiserver.
Instead of changing annotations to demonstrate Updates/Rollbacks, change the container image as it is less confusing for readers and a better real-world example.
Improve comments and README to reflect above changes.

Signed-off-by: John Kelly <jekohk@gmail.com>

Kubernetes-commit: 94f5bcf6f77d5b35074dfab47b5de37096d8ee00
2017-10-05 19:07:57 -04:00

194 lines
5.6 KiB
Go

/*
Copyright 2017 The Kubernetes Authors.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
// Note: the example only works with the code within the same release/branch.
package main
import (
"bufio"
"flag"
"fmt"
"os"
"path/filepath"
appsv1beta1 "k8s.io/api/apps/v1beta1"
apiv1 "k8s.io/api/core/v1"
metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
"k8s.io/client-go/kubernetes"
"k8s.io/client-go/tools/clientcmd"
"k8s.io/client-go/util/retry"
// Uncomment the following line to load the gcp plugin (only required to authenticate against GKE clusters).
// _ "k8s.io/client-go/plugin/pkg/client/auth/gcp"
)
func main() {
var kubeconfig *string
if home := homeDir(); home != "" {
kubeconfig = flag.String("kubeconfig", filepath.Join(home, ".kube", "config"), "(optional) absolute path to the kubeconfig file")
} else {
kubeconfig = flag.String("kubeconfig", "", "absolute path to the kubeconfig file")
}
flag.Parse()
config, err := clientcmd.BuildConfigFromFlags("", *kubeconfig)
if err != nil {
panic(err)
}
clientset, err := kubernetes.NewForConfig(config)
if err != nil {
panic(err)
}
deploymentsClient := clientset.AppsV1beta1().Deployments(apiv1.NamespaceDefault)
deployment := &appsv1beta1.Deployment{
ObjectMeta: metav1.ObjectMeta{
Name: "demo-deployment",
},
Spec: appsv1beta1.DeploymentSpec{
Replicas: int32Ptr(2),
Template: apiv1.PodTemplateSpec{
ObjectMeta: metav1.ObjectMeta{
Labels: map[string]string{
"app": "demo",
},
},
Spec: apiv1.PodSpec{
Containers: []apiv1.Container{
{
Name: "web",
Image: "nginx:1.12",
Ports: []apiv1.ContainerPort{
{
Name: "http",
Protocol: apiv1.ProtocolTCP,
ContainerPort: 80,
},
},
},
},
},
},
},
}
// Create Deployment
fmt.Println("Creating deployment...")
result, err := deploymentsClient.Create(deployment)
if err != nil {
panic(err)
}
fmt.Printf("Created deployment %q.\n", result.GetObjectMeta().GetName())
// Update Deployment
prompt()
fmt.Println("Updating deployment...")
// You have two options to Update() this Deployment:
//
// 1. Modify the "deployment" variable and call: Update(deployment).
// This works like the "kubectl replace" command and it overwrites/loses changes
// made by other clients between you Create() and Update() the object.
// 2. Modify the "result" returned by Get() and retry Update(result) until
// you no longer get a conflict error. This way, you can preserve changes made
// by other clients between Create() and Update(). This is implemented below
// using the retry utility package included with client-go. (RECOMMENDED)
//
// More Info:
// https://github.com/kubernetes/community/blob/master/contributors/devel/api-conventions.md#concurrency-control-and-consistency
err = retry.RetryOnConflict(retry.DefaultRetry, func() (err error) {
// Retrieve the latest version of Deployment before attempting update
// RetryOnConflict uses exponential backoff to avoid exhausting the apiserver
result, err = deploymentsClient.Get("demo-deployment", metav1.GetOptions{})
if err != nil {
panic(fmt.Errorf("Get failed: %+v", err))
}
result.Spec.Replicas = int32Ptr(1) // reduce replica count
result.Spec.Template.Spec.Containers[0].Image = "nginx:1.13" // change nginx version
result, err = deploymentsClient.Update(result)
return
})
if err != nil {
panic(fmt.Errorf("Update failed: %+v", err))
}
fmt.Println("Updated deployment...")
// Rollback Deployment
prompt()
fmt.Println("Rolling back deployment...")
// Once again use RetryOnConflict to avoid update conflicts
err = retry.RetryOnConflict(retry.DefaultRetry, func() (err error) {
result, err = deploymentsClient.Get("demo-deployment", metav1.GetOptions{})
if err != nil {
panic(fmt.Errorf("Get failed: %+v", err))
}
result.Spec.RollbackTo = &appsv1beta1.RollbackConfig{
Revision: 0, // can be specific revision number, or 0 for last revision
}
result, err = deploymentsClient.Update(result)
return
})
if err != nil {
panic(fmt.Errorf("Rollback failed: %+v", err))
}
fmt.Println("Rolled back deployment...")
// List Deployments
prompt()
fmt.Printf("Listing deployments in namespace %q:\n", apiv1.NamespaceDefault)
list, err := deploymentsClient.List(metav1.ListOptions{})
if err != nil {
panic(err)
}
for _, d := range list.Items {
fmt.Printf(" * %s (%d replicas)\n", d.Name, *d.Spec.Replicas)
}
// Delete Deployment
prompt()
fmt.Println("Deleting deployment...")
deletePolicy := metav1.DeletePropagationForeground
if err := deploymentsClient.Delete("demo-deployment", &metav1.DeleteOptions{
PropagationPolicy: &deletePolicy,
}); err != nil {
panic(err)
}
fmt.Println("Deleted deployment.")
}
func prompt() {
fmt.Printf("-> Press Return key to continue.")
scanner := bufio.NewScanner(os.Stdin)
for scanner.Scan() {
break
}
if err := scanner.Err(); err != nil {
panic(err)
}
fmt.Println()
}
func int32Ptr(i int32) *int32 { return &i }
func homeDir() string {
if h := os.Getenv("HOME"); h != "" {
return h
}
return os.Getenv("USERPROFILE") // windows
}