Resource Propagating
The PropagationPolicy and ClusterPropagationPolicy APIs are provided to propagate resources. For the differences between the two APIs, please see here.
Here, we use PropagationPolicy as an example to describe how to propagate resources.
Before you start
Install Karmada and prepare the karmadactl command-line tool.
Deploy a simplest multi-cluster Deployment
Create a PropagationPolicy object
You can propagate a Deployment by creating a PropagationPolicy object defined in a YAML file. For example, this YAML file describes a Deployment object named nginx under default namespace need to be propagated to member1 cluster:
# propagationpolicy.yaml
apiVersion: policy.karmada.io/v1alpha1
kind: PropagationPolicy
metadata:
name: example-policy # The default namespace is `default`.
spec:
resourceSelectors:
- apiVersion: apps/v1
kind: Deployment
name: nginx # If no namespace is specified, the namespace is inherited from the parent object scope.
placement:
clusterAffinity:
clusterNames:
- member1
- Create a propagationPolicy base on the YAML file:
kubectl apply -f propagationpolicy.yaml
- Create a Deployment nginx resource:
kubectl create deployment nginx --image nginx
Note: The resource exists only as a template in karmada. After being propagated to a member cluster, the behavior of the resource is the same as that of a single kubernetes cluster.
Note: Resources and PropagationPolicy are created in no sequence. 3. Display information of the deployment:
karmadactl get deployment
The output is similar to this:
NAME CLUSTER READY UP-TO-DATE AVAILABLE AGE ADOPTION
nginx member1 1/1 1 1 52s Y
- List the pods created by the deployment:
karmadactl get pod -l app=nginx
The output is similar to this:
NAME CLUSTER READY STATUS RESTARTS AGE
nginx-6799fc88d8-s7vv9 member1 1/1 Running 0 52s
Update PropagationPolicy
You can update the propagationPolicy by applying a new YAML file. This YAML file propagates the Deployment to the member2 cluster.
# propagationpolicy-update.yaml
apiVersion: policy.karmada.io/v1alpha1
kind: PropagationPolicy
metadata:
name: example-policy
spec:
resourceSelectors:
- apiVersion: apps/v1
kind: Deployment
name: nginx
placement:
clusterAffinity:
clusterNames: # Modify the selected cluster to propagate the Deployment.
- member2
- Apply the new YAML file:
kubectl apply -f propagationpolicy-update.yaml
- Display information of the deployment (the output is similar to this):
NAME CLUSTER READY UP-TO-DATE AVAILABLE AGE ADOPTION
nginx member2 1/1 1 1 5s Y
- List the pods of the deployment (the output is similar to this):
NAME CLUSTER READY STATUS RESTARTS AGE
nginx-6799fc88d8-8t8cc member2 1/1 Running 0 17s
Update Deployment
You can update the deployment template. The changes will be automatically synchronized to the member clusters.
- Update deployment replicas to 2
- Display information of the deployment (the output is similar to this):
NAME CLUSTER READY UP-TO-DATE AVAILABLE AGE ADOPTION
nginx member2 2/2 2 2 7m59s Y
- List the pods of the deployment (the output is similar to this):
NAME CLUSTER READY STATUS RESTARTS AGE
nginx-6799fc88d8-8t8cc member2 1/1 Running 0 8m12s
nginx-6799fc88d8-zpl4j member2 1/1 Running 0 17s
Delete a propagationPolicy
Delete the propagationPolicy by name:
kubectl delete propagationpolicy example-policy
Deleting a propagationPolicy does not delete deployments propagated to member clusters. You need to delete deployments in the karmada control-plane:
kubectl delete deployment nginx
Deploy deployment into a specified set of target clusters
.spec.placement.clusterAffinity
field of PropagationPolicy represents scheduling restrictions on a certain set of clusters, without which any cluster can be scheduling candidates.
It has four fields to set:
- LabelSelector
- FieldSelector
- ClusterNames
- ExcludeClusters
LabelSelector
LabelSelector is a filter to select member clusters by labels. It uses *metav1.LabelSelector
type. If it is non-nil and non-empty, only the clusters match this filter will be selected.
PropagationPolicy can be configured as follows:
apiVersion: policy.karmada.io/v1alpha1
kind: PropagationPolicy
metadata:
name: test-propagation
spec:
...
placement:
clusterAffinity:
labelSelector:
matchLabels:
location: us
...
PropagationPolicy can also be configured as follows:
apiVersion: policy.karmada.io/v1alpha1
kind: PropagationPolicy
metadata:
name: test-propagation
spec:
...
placement:
clusterAffinity:
labelSelector:
matchExpressions:
- key: location
operator: In
values:
- us
...
For a description of matchLabels
and matchExpressions
, you can refer to Resources that support set-based requirements.
FieldSelector
FieldSelector is a filter to select member clusters by fields. If it is non-nil and non-empty, only the clusters match this filter will be selected.
PropagationPolicy can be configured as follows:
apiVersion: policy.karmada.io/v1alpha1
kind: PropagationPolicy
metadata:
name: nginx-propagation
spec:
...
placement:
clusterAffinity:
fieldSelector:
matchExpressions:
- key: provider
operator: In
values:
- huaweicloud
- key: region
operator: NotIn
values:
- cn-south-1
...
If multiple matchExpressions
are specified in the fieldSelector
, the cluster must match all matchExpressions
.
The key
in matchExpressions
now supports three values: provider
, region
, and zone
, which correspond to the .spec.provider
, .spec.region
, and .spec.zone
fields of the Cluster object, respectively.
The operator
in matchExpressions
now supports In
and NotIn
.
ClusterNames
Users can set the ClusterNames
field to specify the selected clusters.
PropagationPolicy can be configured as follows:
apiVersion: policy.karmada.io/v1alpha1
kind: PropagationPolicy
metadata:
name: nginx-propagation
spec:
...
placement:
clusterAffinity:
clusterNames:
- member1
- member2
...
ExcludeClusters
Users can set the ExcludeClusters
fields to specify the clusters to be ignored.
PropagationPolicy can be configured as follows:
apiVersion: policy.karmada.io/v1alpha1
kind: PropagationPolicy
metadata:
name: nginx-propagation
spec:
...
placement:
clusterAffinity:
exclude:
- member1
- member3
...
Configure PropagationPolicy/ClusterPropagationPolicy priority
If a PropagationPolicy and a ClusterPropagationPolicy match the workload, Karmada will select the PropagationPolicy. If multiple PropagationPolicies match the workload, Karmada will select the one with the highest priority. A PropagationPolicy supports implicit and explicit priorities. The same goes for ClusterPropagationPolicy.
The following takes PropagationPolicy as an example.
Configure explicit priority
The spec.priority
in a PropagationPolicy represents the explicit priority. A greater value means a higher priority.
Note: If not specified, defaults to 0.
Assume there are multiple policies:
# highexplicitpriority.yaml
apiVersion: policy.karmada.io/v1alpha1
kind: PropagationPolicy
metadata:
name: propagation-high-explicit-priority
spec:
resourceSelectors:
- apiVersion: apps/v1
kind: Deployment
labelSelector:
matchLabels:
app: nginx
priority: 2
placement:
clusterAffinity:
clusterNames:
- member1
---
# lowexplicitpriority.yaml
apiVersion: policy.karmada.io/v1alpha1
kind: PropagationPolicy
metadata:
name: propagation-low-explicit-priority
spec:
resourceSelectors:
- apiVersion: apps/v1
kind: Deployment
labelSelector:
matchLabels:
app: nginx
priority: 1
placement:
clusterAffinity:
clusterNames:
- member2
---
# defaultexplicitpriority.yaml
apiVersion: policy.karmada.io/v1alpha1
kind: PropagationPolicy
metadata:
name: propagation-low-explicit-priority
spec:
resourceSelectors:
- apiVersion: apps/v1
kind: Deployment
labelSelector:
matchLabels:
app: nginx
placement:
clusterAffinity:
clusterNames:
- member3
The nginx
deployment in default
namespace will be propagated to cluster member1
.
Configure implicit priority
The spec.resourceSelectors
in a PropagationPolicy represents the implicit priority. The priority order (from low to high) is as follows:
- The PropagationPolicy resourceSelector whose name and labelSelector are empty matches the workload.
- The labelSelector of PropagationPolicy resourceSelector matches the workload.
- The name of PropagationPolicy resourceSelector matches the workload.
Assume there are multiple policies:
# emptymatch.yaml
apiVersion: policy.karmada.io/v1alpha1
kind: PropagationPolicy
metadata:
name: propagation-emptymatch
spec:
resourceSelectors:
- apiVersion: apps/v1
kind: Deployment
placement:
clusterAffinity:
clusterNames:
- member1
---
# labelselectormatch.yaml
apiVersion: policy.karmada.io/v1alpha1
kind: PropagationPolicy
metadata:
name: propagation-labelselectormatch
spec:
resourceSelectors:
- apiVersion: apps/v1
kind: Deployment
labelSelector:
matchLabels:
app: nginx
placement:
clusterAffinity:
clusterNames:
- member2
---
# namematch.yaml
apiVersion: policy.karmada.io/v1alpha1
kind: PropagationPolicy
metadata:
name: propagation-namematch
spec:
resourceSelectors:
- apiVersion: apps/v1
kind: Deployment
name: nginx
placement:
clusterAffinity:
clusterNames:
- member3
The nginx
deployment in default
namespace will be propagated to cluster member3
.
Choose from same-priority PropagationPolicies
If multiple PropagationPolicies with the same explicit priority match the workload, the one with the highest implicit priority will be selected.
Assume there are multiple policies:
# explicit-labelselectormatch.yaml
apiVersion: policy.karmada.io/v1alpha1
kind: PropagationPolicy
metadata:
name: propagation-explicit-labelselectormatch
spec:
resourceSelectors:
- apiVersion: apps/v1
kind: Deployment
labelSelector:
matchLabels:
app: nginx
priority: 3
placement:
clusterAffinity:
clusterNames:
- member1
---
# explicit-namematch.yaml
apiVersion: policy.karmada.io/v1alpha1
kind: PropagationPolicy
metadata:
name: propagation-explicit-namematch
spec:
resourceSelectors:
- apiVersion: apps/v1
kind: Deployment
name: nginx
priority: 3
placement:
clusterAffinity:
clusterNames:
- member3
The nginx
deployment in default
namespace will be propagated to cluster member3
.
If both explicit and implicit priorities are the same, Karmada applies the PropagationPolicy in an ascending alphabetical order, for example, choosing xxx-a-xxx instead of xxx-b-xxx.
Assume there are multiple policies:
# higher-alphabetical.yaml
apiVersion: policy.karmada.io/v1alpha1
kind: PropagationPolicy
metadata:
name: propagation-b-higher-alphabetical
spec:
resourceSelectors:
- apiVersion: apps/v1
kind: Deployment
name: nginx
priority: 3
placement:
clusterAffinity:
clusterNames:
- member1
---
# lower-alphabetical.yaml
apiVersion: policy.karmada.io/v1alpha1
kind: PropagationPolicy
metadata:
name: propagation-a-lower-alphabetical
spec:
resourceSelectors:
- apiVersion: apps/v1
kind: Deployment
name: nginx
priority: 3
placement:
clusterAffinity:
clusterNames:
- member2
The nginx
deployment in default
namespace will be propagated to cluster member2
.
Multi-Cluster Failover
Please refer to Failover feature of Karmada.