Use ASM to balance the load for an application deployed in clusters across regions

Step 1: Deploy an application in clusters across regions

Deploy the Bookinfo application in multiple clusters in VPCs across regions.

Step 2: Enable access to the nearest instance

To detect abnormal microservice instances of the Bookinfo application in a timely manner, you need to use Envoy proxies to configure exception detection in the destination rule for each service. For more information, see Destination Rule. When an Envoy proxy sends a request, ASM prioritizes the workload instances of the target application service based on the location of the Envoy proxy. If you enable the access to the nearest instance and all workload instances are normal, requests from Envoy proxies are preferentially sent to the nearest instances.

1. Log on to the ASM console.
2. In the left-side navigation pane, choose Service Mesh > Mesh Management.
3. On the Mesh Management page, click the name of the target ASM instance or click Manage in the Actions column.
4. In the Basic Information section, click Settings in the upper-right corner.
5. In the Settings Update pane, select Enable Access to Nearest Nodes.
6. Click OK.
   In the Basic Information section, you can find that the status in the Access Nearest Nodes field changes to Enable.

Step 3: Configure exception detection

Requests are sent to the workload instance that is nearest to the source Envoy proxy only when the workload instance runs normally. Therefore, you need to configure exception detection in the destination rule for the target microservice so that Envoy proxies can check whether the nearest workload instance is normal.

1. Log on to the ASM console.
2. In the left-side navigation pane, choose Service Mesh > Mesh Management.
3. On the Mesh Management page, click the name of the target ASM instance or click Manage in the Actions column.
4. In the Control Plane section, click the Destination Rule tab and then Create.
5. In the Create pane, define a destination rule and click OK.
   1. In the Namespace drop-down list, select the namespace in which you want to define the destination rule.
   2. In the code editor, enter the configuration information for the destination rule.
      The content of the YAML file is as follows:

      apiVersion: networking.istio.io/v1alpha3
      kind: DestinationRule
      metadata:
        name: reviews
      spec:
        host: reviews
        trafficPolicy:
          outlierDetection:
            consecutiveErrors: 5
            interval: 2m
            baseEjectionTime: 5m

   On the Destination Rule tab, you can view the defined destination rule.