Configuring Weights for StatefulSet Backend Pods in a LoadBalancer Service

Prerequisites

• A CCE Turbo cluster is available, as this function is not supported by other cluster types.
• The cluster version must meet the following requirements:
  • v1.29: v1.29.15-r60 or later
  • v1.30: v1.30.14-r60 or later
  • v1.31: v1.31.14-r20 or later
  • v1.32: v1.32.9-r20 or later
  • v1.33: v1.33.7-r20 or later
  • v1.34: v1.34.3-r10 or later
  • v1.35: v1.35.1-r0 or later
  • Clusters of later versions

Notes and Constraints

• This function is available only for dedicated load balancers.
• This function is incompatible with dynamic backend weight adjustment for backend cloud servers (kubernetes.io/elb.adaptive-weight).
• When used with cross-cluster access, the kubernetes.io/elb.multicluster-loadbalancer-weight annotation is also unsupported.

Using kubectl

1. Use kubectl to access the cluster. For details, see Accessing a Cluster Using kubectl.
2. Create a YAML file named service-test.yaml. The file name can be customized.

   vi service-test.yaml

   The following is an example YAML file of an ingress associated with an existing load balancer:

   apiVersion: v1
   kind: Service
   metadata:
     name: test
     labels:
       app: test-state
       version: v1
     namespace: default
     annotations:
       kubernetes.io/elb.class: performance   # Load balancer type. Only dedicated load balancers are supported.
       kubernetes.io/elb.id: <your_elb_id>   # Load balancer ID. Replace it with the actual value.
       #  Configure the weights of StatefulSet backend pods.
       kubernetes.io/elb.custom-backend-weights: |
         {
           "defaultWeight": 12,
           "groups": [
             {
               "listener": {
                 "protocol": "TCP",
                 "port": 978
               },
               "statefulSets": [
                 {
                   "name": "test-state",
                   "weights": [
                     {
                       "weight": 18,
                       "podIndexes": [1]
                     }
                   ]
                 }
               ]
             }
           ]
         }
   spec:
     selector:  # The Service must be associated with StatefulSet workloads.
       app: test-state
       version: v1
     externalTrafficPolicy: Cluster
     ports:
       - name: cce-service-0
         targetPort: 80
         nodePort: 0
         port: 978
         protocol: TCP
     type: LoadBalancer
     loadBalancerIP: 192.168.0.6

   Table 1 kubernetes.io/elb.custom-backend-weights data structure

   Parameter	Mandatory	Type	Description
   defaultWeight	Yes	Integer	The default backend weight. Pods without an explicitly assigned weight will use this default value. Value range: 1 to 100
   groups	No	Array of WeightGroup Object	Weight rule groups, where each group corresponds to the backend servers attached to a listener.

   Table 2 WeightGroup data structure

   Parameter	Mandatory	Type	Description
   listener	Yes	Listener Object	Target listener to be matched.
   statefulSets	Yes	Array of StatefulSet Object	StatefulSets for which weights are to be configured.

   Table 3 Listener data structure

   Parameter	Mandatory	Type	Description
   protocol	Yes	String	Listener protocol, which must match the protocol of the Service's associated listener.
   port	Yes	Integer	Listener port, which must match the port on the Service's associated listener.

   Table 4 StatefulSet data structure

   Parameter	Mandatory	Type	Description
   name	Yes	String	StatefulSet name, which must match the name of the StatefulSet actually associated with the Service. If none of the workloads associated with the Service matches this name, or the matched workload is not a StatefulSet, the weight configuration is ignored.
   weights	Yes	Array of Weight Object	Weights of the pods in the StatefulSet.

   Table 5 Weight data structure

   Parameter	Mandatory	Type	Description
   weight	Yes	String	Traffic weight allocated to a specified pod. Value range: 1 to 100
   podIndexes	Yes	Array of Integer	List of pod indexes that use this weight. For example, [1] in the example indicates pod test-state-1.

3. Create the Service.

   kubectl create -f service-test.yaml

   If information similar to the following is displayed, the Service has been created:

   service/service-test created

Verifying Weight Settings

1. Log in to the CCE console and click the cluster name to access the cluster console.
2. In the navigation pane, choose Services and Ingresses. Locate the row that contains the created Service and click the load balancer name to go to the ELB console.
3. Switch to the Listeners tab page. Check whether a supplementary network interface is bound to the listener's backend server and whether the weight meets expectations.

   

Helpful Links

With cross-cluster backend servers enabled (kubernetes.io/elb.multicluster: 'true'), you can use kubernetes.io/elb.custom-backend-weights to configure weights for individual StatefulSet backend pods. For details about the applications and configurations of cross-cluster backend servers, see Configuring Multiple Cross-Cluster Backend Servers for a LoadBalancer Service. You only need to replace the kubernetes.io/elb.multicluster-loadbalancer-weight settings with the kubernetes.io/elb.custom-backend-weights settings.

The StatefulSet settings in kubernetes.io/elb.custom-backend-weights apply only to a Service's backend servers. Therefore, when using cross-cluster backend servers, configure both kubernetes.io/elb.multicluster and kubernetes.io/elb.custom-backend-weights for Services in each cluster.