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doc: migrate existing resource from a cluster to Karmada.
Signed-off-by: chaosi-zju <chaosi@zju.edu.cn>
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--- | ||
title: Migrate In Batch | ||
--- | ||
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## Scenario | ||
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Assuming the user has a single kubernetes cluster which already has many native resource installed. | ||
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The user want to install Karmada for multi-cluster management, and hope to migrate the resource that already exist from original cluster to Karmada. | ||
It is required that the pods already exist not be affected during the process of migration, which means the relevant container not be restarted. | ||
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So, how to migrate the existing resource? | ||
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![](../../resources/administrator/migrate-in-batch-1.jpg) | ||
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## Recommended migration strategy | ||
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If you only want to migrate individual resources, you can just refer to [promote-legacy-workload](./promote-legacy-workload) to do it one by one. | ||
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If you want to migrate a batch of resources, you are advised to take over all resources based on resource granularity through few `PropagationPolicy` at first, | ||
then if you have more propagate demands based on application granularity, you can apply higher priority `PropagationPolicy` to preempt them. | ||
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Thus, how to take over all resources based on resource granularity? You can do as follows. | ||
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![](../../resources/administrator/migrate-in-batch-2.jpg) | ||
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### Step one | ||
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Since the existing resources will be token over by Karmada, there is no longer need to apply the related YAML config to member cluster. | ||
That means, you can stop the corresponding operation or pipeline. | ||
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### Step two | ||
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Apply all the YAML config of resources to Karmada control plane, as the [ResourceTemplate](https://karmada.io/docs/core-concepts/concepts#resource-template) of Karmada. | ||
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### Step three | ||
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Edit a [PropagationPolicy](https://karmada.io/docs/core-concepts/concepts#propagation-policy), and apply it to Karmada control plane. You should pay attention to two fields: | ||
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* `spec.conflictResolution: Overwrite`:**the value must be [Overwrite](https://github.com/karmada-io/karmada/blob/master/docs/proposals/migration/design-of-seamless-cluster-migration-scheme.md#proposal).** | ||
* `spec.resourceSelectors`:defining which resources are selected to migrate | ||
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here we provide two examples: | ||
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#### Eg1. migrate all deployments | ||
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If you want to migrate all deployments from `member1` cluster to Karmada, you shall apply: | ||
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```yaml | ||
apiVersion: policy.karmada.io/v1alpha1 | ||
kind: PropagationPolicy | ||
metadata: | ||
name: deployments-pp | ||
spec: | ||
conflictResolution: Overwrite | ||
placement: | ||
clusterAffinity: | ||
clusterNames: | ||
- member1 | ||
priority: 0 | ||
resourceSelectors: | ||
- apiVersion: apps/v1 | ||
kind: Deployment | ||
schedulerName: default-scheduler | ||
``` | ||
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#### Eg2. migrate all services | ||
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If you want to migrate all services from `member1` cluster to Karmada, you shall apply: | ||
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```yaml | ||
apiVersion: policy.karmada.io/v1alpha1 | ||
kind: PropagationPolicy | ||
metadata: | ||
name: services-pp | ||
spec: | ||
conflictResolution: Overwrite | ||
placement: | ||
clusterAffinity: | ||
clusterNames: | ||
- member1 | ||
priority: 0 | ||
resourceSelectors: | ||
- apiVersion: v1 | ||
kind: Service | ||
schedulerName: default-scheduler | ||
``` | ||
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### Step four | ||
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The rest migration operations will be finished by Karmada automatically. | ||
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## PropagationPolicy Preemption and Demo | ||
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Besides, if you have more propagate demands based on application granularity, you can apply higher priority `PropagationPolicy` | ||
to preempt those you applied in the migration mentioned above. Detail demo you can refer to the tutorial [Resource Migration](../../tutorials/resource-migration.md) | ||
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--- | ||
title: Resource Migration | ||
--- | ||
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## Objectives | ||
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Assuming you have a single kubernetes cluster which already has many native resource installed, furthermore, | ||
you want to migrate the existing resource to Karmada and then achieve multi-cluster management. | ||
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So, this section will guide you to cover: | ||
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- Migrate all the existing resource from original cluster to Karmada based on resource granularity. | ||
- Apply higher priority `PropagationPolicy` to meet more propagate demands based on application granularity. | ||
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## Prerequisites | ||
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### Karmada with multi cluster has been installed | ||
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**Step 1: Run the command** | ||
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```shell | ||
$ git clone https://github.com/karmada-io/karmada | ||
$ cd karmada | ||
$ hack/local-up-karmada.sh | ||
$ export KUBECONFIG=~/.kube/karmada.config:~/.kube/members.config | ||
``` | ||
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**Note:** | ||
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Before guide started, we should install at least three kubernetes clusters, one is for Karmada control plane, the other two for business clusters. | ||
For convenience, we use [hack/local-up-karmada.sh](https://karmada.io/docs/installation/#install-karmada-for-development-environment) script to quickly prepare the above clusters. | ||
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After the above command executed, you will see Karmada control plane installed with multi members clusters. | ||
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### Enable PropagationPolicyPreemption in karmada-controller-manager | ||
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**Step 2: Run the command** | ||
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```shell | ||
$ kubectl --context karmada-host get deploy karmada-controller-manager -n karmada-system -o yaml | sed '/- --failover-eviction-timeout=30s/{n;s/- --v=4/- --feature-gates=PropagationPolicyPreemption=true\n &/g}' | kubectl --context karmada-host replace -f - | ||
``` | ||
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**Note:** | ||
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The feature `PropagationPolicy Priority and Preemption` was introduced in v1.7, and it is controlled by the feature gate `PropagationPolicyPreemption` which is disabled by default. | ||
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You can just execute the above one command to enable this feature gate. Or, if you want to use a more cautious approach, you can do like this: | ||
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1. execute `kubectl --context karmada-host edit deploy karmada-controller-manager -n karmada-system` | ||
2. check if feature gate `--feature-gates=PropagationPolicyPreemption=true` is existed in `spec.template.spec.containers[0].command` field. | ||
3. If not, you shall add `--feature-gates=PropagationPolicyPreemption=true` into that field. | ||
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### Preset resource in a member cluster | ||
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To simulate resources already exist in the member cluster, we deploy some simple Deployments and Services to `member1` cluster. | ||
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**Step 3: Write the code** | ||
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Create new file `/tmp/deployments-and-services.yaml` and copy text below to it: | ||
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```yaml | ||
apiVersion: apps/v1 | ||
kind: Deployment | ||
metadata: | ||
name: nginx-deploy | ||
spec: | ||
selector: | ||
matchLabels: | ||
app: nginx | ||
replicas: 2 | ||
template: | ||
metadata: | ||
labels: | ||
app: nginx | ||
spec: | ||
containers: | ||
- name: nginx | ||
image: nginx:latest | ||
ports: | ||
- containerPort: 80 | ||
--- | ||
apiVersion: v1 | ||
kind: Service | ||
metadata: | ||
name: nginx-svc | ||
spec: | ||
selector: | ||
app: nginx | ||
type: NodePort | ||
ports: | ||
- port: 80 | ||
nodePort: 30000 | ||
targetPort: 80 | ||
``` | ||
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**Step 4: Run the command** | ||
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```shell | ||
$ kubectl --context member1 apply -f /tmp/deployments-and-services.yaml | ||
deployment.apps/nginx-deploy created | ||
service/nginx-svc created | ||
deployment.apps/hello-deploy created | ||
service/hello-svc created | ||
``` | ||
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Thus, we can use `member1` as the cluster with existing resources, while `member2` as a bare cluster. | ||
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## Tutorials | ||
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### Migrate all the resources to Karmada | ||
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1)Apply the local file `/tmp/deployments-and-services.yaml` written just now to Karmada control plane too. | ||
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**Step 5: Run the command** | ||
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```shell | ||
➜ ✗ kubectl --context karmada-apiserver apply -f /tmp/deployments-and-services.yaml | ||
deployment.apps/nginx-deploy created | ||
service/nginx-svc created | ||
deployment.apps/hello-deploy created | ||
service/hello-svc created | ||
``` | ||
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2)Write a `PropagationPolicy` to the local file `/tmp/pp-for-migrating-deployments-and-services.yaml`. | ||
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**Step 6: Write the code** | ||
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Create new file `/tmp/pp-for-migrating-deployments-and-services.yaml` and copy text below to it: | ||
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```yaml | ||
apiVersion: policy.karmada.io/v1alpha1 | ||
kind: PropagationPolicy | ||
metadata: | ||
name: migrate-pp | ||
spec: | ||
conflictResolution: Overwrite | ||
placement: | ||
clusterAffinity: | ||
clusterNames: | ||
- member1 | ||
priority: 0 | ||
resourceSelectors: | ||
- apiVersion: apps/v1 | ||
kind: Deployment | ||
- apiVersion: v1 | ||
kind: Service | ||
schedulerName: default-scheduler | ||
``` | ||
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**Note:** | ||
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You should pay attention to two fields: | ||
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* `spec.conflictResolution: Overwrite`:the value must be [Overwrite](https://github.com/karmada-io/karmada/blob/master/docs/proposals/migration/design-of-seamless-cluster-migration-scheme.md#proposal). | ||
* `spec.resourceSelectors`:selecting resources to migrate, you can define your custom [ResourceSelector](https://karmada.io/docs/userguide/scheduling/override-policy/#resource-selector). | ||
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3)Apply `/tmp/pp-for-migrating-deployments-and-services.yaml` to Karmada control plane. | ||
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**Step 7: Run the command** | ||
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```shell | ||
$ kubectl --context karmada-apiserver apply -f /tmp/pp-for-migrating-deployments-and-services.yaml | ||
propagationpolicy.policy.karmada.io/migrate-pp created | ||
``` | ||
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Now, you have finished the migration, isn't it so easy? | ||
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4)Verification | ||
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**Step 8: Run the command** | ||
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```shell | ||
$ kubectl --context karmada-apiserver get deploy | ||
$ kubectl --context karmada-apiserver get rb | ||
``` | ||
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You can see the Deployments in Karmada are all ready and the `aggregatedStatus` of `ResourceBinding` is applied. | ||
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### Apply higher priority PropagationPolicy | ||
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1)Write a high priority `PropagationPolicy` to the local file `/tmp/pp-for-nginx-app.yaml`. | ||
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**Step 9: Write the code** | ||
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Create new file `/tmp/pp-for-nginx-app.yaml` and copy text below to it: | ||
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```yaml | ||
apiVersion: policy.karmada.io/v1alpha1 | ||
kind: PropagationPolicy | ||
metadata: | ||
name: nginx-pp | ||
spec: | ||
conflictResolution: Overwrite | ||
placement: | ||
clusterAffinity: | ||
clusterNames: | ||
- member1 | ||
- member2 ## focus on this line | ||
priority: 10 | ||
preemption: Always ## focus on this line | ||
resourceSelectors: | ||
- apiVersion: apps/v1 | ||
kind: Deployment | ||
name: nginx-deploy | ||
- apiVersion: v1 | ||
kind: Service | ||
name: nginx-svc | ||
schedulerName: default-scheduler | ||
``` | ||
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2)Apply `/tmp/pp-for-nginx-app.yaml` to Karmada control plane. | ||
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**Step 10: Run the command** | ||
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```shell | ||
$ kubectl --context karmada-apiserver apply -f /tmp/pp-for-nginx-app.yaml | ||
propagationpolicy.policy.karmada.io/nginx-pp created | ||
``` | ||
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3)Verification | ||
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**Step 11: Run the command** | ||
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```shell | ||
$ kubectl --context member2 get deploy -o wide | ||
NAME READY UP-TO-DATE AVAILABLE AGE CONTAINERS IMAGES SELECTOR | ||
nginx-deploy 2/2 2 2 5m24s nginx nginx:latest app=nginx | ||
$ kubectl --context member2 get svc -o wide | ||
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR | ||
nginx-svc NodePort 10.13.161.255 <none> 80:30000/TCP 54s app=nginx | ||
... | ||
``` | ||
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As you see, you would find `nginx` application related resource are all propagated to `member2` cluster, | ||
which means the higher priority `PropagationPolicy` does work. |
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