Merge pull request #53474 from jekohk/clientgo-examples/crud-rollback

Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

client-go/examples: Update CRUD Deployment sample

**What this PR does / why we need it**:
PR motivated by [#128](https://github.com/kubernetes/client-go/issues/128), namely updating the CRUD example with the following:
- Add new step which demonstrates rolling back deployments
- Cleanup retry loop for `Update()` steps
- Make `-kubeconfig` flag optional when running example (same as out-of-cluster example)
- Update `README.md` to reflect changes

**Special notes for your reviewer**:
My first Kubernetes contribution- feedback very welcome!

**Release note**:

```release-note
NONE
```

/cc @ahmetb @caesarxuchao

Kubernetes-commit: 1ba331ef59220c3f50246a4bfe23350de2c2f5ed
This commit is contained in:
Kubernetes Publisher 2017-10-24 19:01:34 -07:00
commit 19f27357d1
4 changed files with 767 additions and 732 deletions

1392
Godeps/Godeps.json generated

File diff suppressed because it is too large Load Diff

View File

@ -19,10 +19,11 @@ go_library(
deps = [
"//vendor/k8s.io/api/apps/v1beta1:go_default_library",
"//vendor/k8s.io/api/core/v1:go_default_library",
"//vendor/k8s.io/apimachinery/pkg/api/errors:go_default_library",
"//vendor/k8s.io/apimachinery/pkg/apis/meta/v1:go_default_library",
"//vendor/k8s.io/client-go/kubernetes:go_default_library",
"//vendor/k8s.io/client-go/tools/clientcmd:go_default_library",
"//vendor/k8s.io/client-go/util/homedir:go_default_library",
"//vendor/k8s.io/client-go/util/retry:go_default_library",
],
)

View File

@ -22,6 +22,8 @@ go build -o ./app
Now, run this application on your workstation with your local kubeconfig file:
```
./app
# or specify a kubeconfig file with flag
./app -kubeconfig=$HOME/.kube/config
```
@ -30,13 +32,19 @@ Running this command will execute the following operations on your cluster:
1. **Create Deployment:** This will create a 2 replica Deployment. Verify with
`kubectl get pods`.
2. **Update Deployment:** This will update the Deployment resource created in
previous step to set the replica count to 1 and add annotations. You are
encouraged to inspect the retry loop that handles conflicts. Verify the new
replica count and `foo=bar` annotation with `kubectl describe deployment
demo`.
3. **List Deployments:** This will retrieve Deployments in the `default`
previous step by setting the replica count to 1 and changing the container
image to `nginx:1.13`. You are encouraged to inspect the retry loop that
handles conflicts. Verify the new replica count and container image with
`kubectl describe deployment demo`.
3. **Rollback Deployment:** This will rollback the Deployment to the last
revision. In this case, it's the revision that was created in Step 1.
Use `kubectl describe` to verify the container image is now `nginx:1.12`.
Also note that the Deployment's replica count is still 1; this is because a
Deployment revision is created if and only if the Deployment's pod template
(`.spec.template`) is changed.
4. **List Deployments:** This will retrieve Deployments in the `default`
namespace and print their names and replica counts.
4. **Delete Deployment:** This will delete the Deployment object and its
5. **Delete Deployment:** This will delete the Deployment object and its
dependent ReplicaSet resource. Verify with `kubectl get deployments`.
Each step is separated by an interactive prompt. You must hit the
@ -55,6 +63,10 @@ Updating deployment...
Updated deployment...
-> Press Return key to continue.
Rolling back deployment...
Rolled back deployment...
-> Press Return key to continue.
Listing deployments in namespace "default":
* demo-deployment (1 replicas)
-> Press Return key to continue.

View File

@ -22,23 +22,28 @@ import (
"flag"
"fmt"
"os"
"path/filepath"
appsv1beta1 "k8s.io/api/apps/v1beta1"
apiv1 "k8s.io/api/core/v1"
"k8s.io/apimachinery/pkg/api/errors"
metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
"k8s.io/client-go/kubernetes"
"k8s.io/client-go/tools/clientcmd"
"k8s.io/client-go/util/homedir"
"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() {
kubeconfig := flag.String("kubeconfig", "", "absolute path to the kubeconfig file")
flag.Parse()
if *kubeconfig == "" {
panic("-kubeconfig not specified")
var kubeconfig *string
if home := homedir.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)
@ -66,7 +71,7 @@ func main() {
Containers: []apiv1.Container{
{
Name: "web",
Image: "nginx:1.13",
Image: "nginx:1.12",
Ports: []apiv1.ContainerPort{
{
Name: "http",
@ -97,36 +102,53 @@ func main() {
// 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 Create()/Get() and retry Update(result) until
// 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:
// 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
for {
result.Spec.Replicas = int32Ptr(1) // reduce replica count
result.Spec.Template.Annotations = map[string]string{ // add annotations
"foo": "bar",
retryErr := retry.RetryOnConflict(retry.DefaultRetry, func() error {
// Retrieve the latest version of Deployment before attempting update
// RetryOnConflict uses exponential backoff to avoid exhausting the apiserver
result, getErr := deploymentsClient.Get("demo-deployment", metav1.GetOptions{})
if getErr != nil {
panic(fmt.Errorf("Failed to get latest version of Deployment: %v", getErr))
}
if _, err := deploymentsClient.Update(result); errors.IsConflict(err) {
// Deployment is modified in the meanwhile, query the latest version
// and modify the retrieved object.
fmt.Println("encountered conflict, retrying")
result, err = deploymentsClient.Get("demo-deployment", metav1.GetOptions{})
if err != nil {
panic(fmt.Errorf("Get failed: %+v", err))
}
} else if err != nil {
panic(err)
} else {
break
}
// TODO: You should sleep here with an exponential backoff to avoid
// exhausting the apiserver, and add a limit/timeout on the retries to
// avoid getting stuck in this loop indefintiely.
result.Spec.Replicas = int32Ptr(1) // reduce replica count
result.Spec.Template.Spec.Containers[0].Image = "nginx:1.13" // change nginx version
_, updateErr := deploymentsClient.Update(result)
return updateErr
})
if retryErr != nil {
panic(fmt.Errorf("Update failed: %v", retryErr))
}
fmt.Println("Updated deployment...")
// Rollback Deployment
prompt()
fmt.Println("Rolling back deployment...")
// Once again use RetryOnConflict to avoid update conflicts
retryErr = retry.RetryOnConflict(retry.DefaultRetry, func() error {
result, getErr := deploymentsClient.Get("demo-deployment", metav1.GetOptions{})
if getErr != nil {
panic(fmt.Errorf("Failed to get latest version of Deployment: %v", getErr))
}
result.Spec.RollbackTo = &appsv1beta1.RollbackConfig{
Revision: 0, // can be specific revision number, or 0 for last revision
}
_, updateErr := deploymentsClient.Update(result)
return updateErr
})
if retryErr != nil {
panic(fmt.Errorf("Rollback failed: %v", retryErr))
}
fmt.Println("Rolled back deployment...")
// List Deployments
prompt()
fmt.Printf("Listing deployments in namespace %q:\n", apiv1.NamespaceDefault)