Version 1.11

Set up a multi-cluster mesh on GKE

This guide explains how to join two clusters into a single Anthos Service Mesh using Mesh CA or Istio CA, and enable cross-cluster load balancing. You can easily extend this process to incorporate any number of clusters into your mesh.

A multi-cluster Anthos Service Mesh configuration can solve several crucial enterprise scenarios, such as scale, location, and isolation. For more information, see Multi-cluster use cases.

Prerequisites

This guide assumes that you have two or more Google Cloud GKE clusters that meet the following requirements:

Setting project and cluster variables

Create the following environment variables for the project ID, cluster zone or region, cluster name, and context

```sh
export PROJECT_1=PROJECT_ID_1
export LOCATION_1=CLUSTER_LOCATION_1
export CLUSTER_1=CLUSTER_NAME_1
export CTX_1="gke_${PROJECT_1}_${LOCATION_1}_${CLUSTER_1}"

export PROJECT_2=PROJECT_ID_2
export LOCATION_2=CLUSTER_LOCATION_2
export CLUSTER_2=CLUSTER_NAME_2
export CTX_2="gke_${PROJECT_2}_${LOCATION_2}_${CLUSTER_2}"
```

Create firewall rule

In some cases, you need to create a firewall rule to allow cross-cluster traffic. For example, you need to create a firewall rule if:

  • You use different subnets for the clusters in your mesh.
  • Your Pods open ports other than 443 and 15002.

GKE automatically adds firewall rules to each node to allow traffic within the same subnet. If your mesh contains multiple subnets, you must explicitly set up the firewall rules to allow cross-subnet traffic. You must add a new firewall rule for each subnet to allow the source IP CIDR blocks and targets ports of all the incoming traffic.

The following instructions allow communication between all clusters in your project or only between $CLUSTER_1 and $CLUSTER_2.

  1. Gather information about your clusters' network.

    All project clusters

    The following command allows communication between all clusters in your project. If there are clusters in your project that you don't want to expose use the command in the Specific clusters tab.

    function join_by { local IFS="$1"; shift; echo "$*"; }
    ALL_CLUSTER_CIDRS=$(gcloud --project $PROJECT_ID container clusters list --format='value(clusterIpv4Cidr)' | sort | uniq)
    ALL_CLUSTER_CIDRS=$(join_by , $(echo "${ALL_CLUSTER_CIDRS}"))
    ALL_CLUSTER_NETTAGS=$(gcloud --project $PROJECT_ID compute instances list --format='value(tags.items.[0])' | sort | uniq)
    ALL_CLUSTER_NETTAGS=$(join_by , $(echo "${ALL_CLUSTER_NETTAGS}"))
    

    Specific clusters

    The following command allows communication between $CLUSTER_1 and $CLUSTER_2 and doesn't expose other clusters in your project.

    function join_by { local IFS="$1"; shift; echo "$*"; }
    ALL_CLUSTER_CIDRS=$(gcloud --project $PROJECT_ID container clusters list --filter="name=($CLUSTER_1,$CLUSTER_2)" --format='value(clusterIpv4Cidr)' | sort | uniq)
    ALL_CLUSTER_CIDRS=$(join_by , $(echo "${ALL_CLUSTER_CIDRS}"))
    ALL_CLUSTER_NETTAGS=$(gcloud --project $PROJECT_ID compute instances list --filter="name=($CLUSTER_1,$CLUSTER_2)" --format='value(tags.items.[0])' | sort | uniq)
    ALL_CLUSTER_NETTAGS=$(join_by , $(echo "${ALL_CLUSTER_NETTAGS}"))
    
  2. Create the firewall rule.

    gcloud compute firewall-rules create istio-multicluster-pods \
        --allow=tcp,udp,icmp,esp,ah,sctp \
        --direction=INGRESS \
        --priority=900 \
        --source-ranges="${ALL_CLUSTER_CIDRS}" \
        --target-tags="${ALL_CLUSTER_NETTAGS}" --quiet
    

Configure endpoint discovery between clusters

To configure endpoint discovery between GKE clusters, you run asmcli create-mesh. This command:

  • Registers all clusters to the same fleet.
  • Configures the mesh to trust the fleet workload identity.
  • Creates remote secrets.

You can either specify the URI for each cluster or the path the kubeconfig file.

Cluster URI

In the following command, replace FLEET_PROJECT_ID with the project ID of the fleet host project and the cluster URI with the cluster name, zone or region, and project ID for each cluster. This example only shows two clusters, but you can run the command to enable endpoint discovery on additional clusters, subject to the GKE Hub service limit.

./asmcli create-mesh \
    FLEET_PROJECT_ID \
    ${PROJECT_1}/${LOCATION_1}/${CLUSTER_1} \
    ${PROJECT_2}/${LOCATION_2}/${CLUSTER_2}

kubeconfig file

In the following command, replace FLEET_PROJECT_ID with the project ID of the fleet host project and PATH_TO_KUBECONFIG with the path to each kubeconfig file. This example only shows two clusters, but you can run the command to enable endpoint discovery on additional clusters, subject to the GKE Hub service limit.

./asmcli create-mesh \
    FLEET_PROJECT_ID \
    PATH_TO_KUBECONFIG_1 \
    PATH_TO_KUBECONFIG_2

Skip to Create a firewall rule.

Configure endpoint discovery between private clusters

When using private clusters, you must configure the remote clusters' private IPs instead of the public IPs because the public IPs are not accessible.

  1. Write the secrets with public IPs into temporary files:

    istioctl x create-remote-secret --context=${CTX_1} --name=${CLUSTER_1} > ${CTX_1}.secret
    
    istioctl x create-remote-secret --context=${CTX_2} --name=${CLUSTER_2} > ${CTX_2}.secret
    
  2. Retrieve the private IPs for the private clusters, and replace the public IPs with them in the secrets in the temporary files:

    PRIV_IP=`gcloud container clusters describe "${CLUSTER_1}" --project "${PROJECT_1}" \
     --zone "${LOCATION_1}" --format "value(privateClusterConfig.privateEndpoint)"`
    
    istioctl x create-remote-secret --context=${CTX_1} --name=${CLUSTER_1} --server=${PRIV_IP} > ${CTX_1}.secret
    
    PRIV_IP=`gcloud container clusters describe "${CLUSTER_2}" --project "${PROJECT_2}" \
     --zone "${LOCATION_12" --format "value(privateClusterConfig.privateEndpoint)"`
    
    istioctl x create-remote-secret --context=${CTX_2} --name=${CLUSTER_2} --server=${PRIV_IP} > ${CTX_2}.secret
    
  3. Apply the new secrets into the clusters:

    kubectl apply -f ${CTX_1}.secret --context=${CTX_2}
    
    kubectl apply -f ${CTX_2}.secret --context=${CTX_1}
    

Configuring authorized networks for private clusters

Follow this section only if all of the following conditions apply to your mesh:

When deploying multiple private clusters, the Anthos Service Mesh control plane in each cluster needs to call the GKE control plane of the remote clusters. To allow traffic, you need to add the Pod address range in the calling cluster to the authorized networks of the remote clusters.

  1. Get the Pod IP CIDR block for each cluster:

    POD_IP_CIDR_1=`gcloud container clusters describe ${CLUSTER_1} --project ${PROJECT_1} --zone ${LOCATION_1} \
      --format "value(ipAllocationPolicy.clusterIpv4CidrBlock)"`
    
    POD_IP_CIDR_2=`gcloud container clusters describe ${CLUSTER_2} --project ${PROJECT_2} --zone ${LOCATION_2} \
      --format "value(ipAllocationPolicy.clusterIpv4CidrBlock)"`
    
  2. Add the Kubernetes cluster Pod IP CIDR blocks to the remote clusters:

    EXISTING_CIDR_1=`gcloud container clusters describe ${CLUSTER_1} --project ${PROJECT_1} --zone ${LOCATION_1} \
     --format "value(masterAuthorizedNetworksConfig.cidrBlocks.cidrBlock)"`
    gcloud container clusters update ${CLUSTER_1} --project ${PROJECT_1} --zone ${LOCATION_1} \
    --enable-master-authorized-networks \
    --master-authorized-networks ${POD_IP_CIDR_2},${EXISTING_CIDR_1//;/,}
    
    EXISTING_CIDR_2=`gcloud container clusters describe ${CLUSTER_2} --project ${PROJECT_2} --zone ${LOCATION_2} \
     --format "value(masterAuthorizedNetworksConfig.cidrBlocks.cidrBlock)"`
    gcloud container clusters update ${CLUSTER_2} --project ${PROJECT_2} --zone ${LOCATION_2} \
    --enable-master-authorized-networks \
    --master-authorized-networks ${POD_IP_CIDR_1},${EXISTING_CIDR_2//;/,}
    

    For more information, see Creating a cluster with authorized networks.

  3. Verify that the authorized networks are updated:

    gcloud container clusters describe ${CLUSTER_1} --project ${PROJECT_1} --zone ${LOCATION_1} \
     --format "value(masterAuthorizedNetworksConfig.cidrBlocks.cidrBlock)"
    
    gcloud container clusters describe ${CLUSTER_2} --project ${PROJECT_2} --zone ${LOCATION_2} \
     --format "value(masterAuthorizedNetworksConfig.cidrBlocks.cidrBlock)"
    

Enable control plane global access

Follow this section only if all of the following conditions apply to your mesh:

  • You are using private clusters.
  • You use different regions for the clusters in your mesh.

You must enable control plane global access to allow Anthos Service Mesh control plane in each cluster to call the GKE control plane of the remote clusters.

  1. Enable control plane global access:

    gcloud container clusters update ${CLUSTER_1} --project ${PROJECT_1} --zone ${LOCATION_1} \
     --enable-master-global-access
    
    gcloud container clusters update ${CLUSTER_2} --project ${PROJECT_2} --zone ${LOCATION_2} \
     --enable-master-global-access
    
  2. Verify that control plane global access in enabled:

    gcloud container clusters describe ${CLUSTER_1} --zone ${LOCATION_1}
    
    gcloud container clusters describe ${CLUSTER_2} --zone ${LOCATION_2}
    

    The privateClusterConfig section in the output displays the status of masterGlobalAccessConfig.

Verify your deployment

This section explains how to deploy the sample HelloWorld and Sleep services to your multi-cluster environment to verify that cross-cluster load balancing works. The samples are located in a subdirectory in the --output_dir directory that you specified in the asmcli install command. For convenience, set the following environment variable:

export SAMPLES_DIR=OUTPUT_DIR/istio-1.11.2-asm.17

Enable sidecar injection

  1. Use the following command to locate the revision label value from the istiod service, which you use in later steps.

    kubectl -n istio-system get pods -l app=istiod --show-labels

    The output looks similar to the following:

    NAME                                READY   STATUS    RESTARTS   AGE   LABELS
    istiod-asm-173-3-5788d57586-bljj4   1/1     Running   0          23h   app=istiod,istio.io/rev=asm-173-3,istio=istiod,pod-template-hash=5788d57586
    istiod-asm-173-3-5788d57586-vsklm   1/1     Running   1          23h   app=istiod,istio.io/rev=asm-173-3,istio=istiod,pod-template-hash=5788d57586
    

    In the output, under the LABELS column, note the value of the istiod revision label, which follows the prefix istio.io/rev=. In this example, the value is asm-173-3. Use the revision value in the steps in the next section.

Install the HelloWorld service

  1. Create the sample namespace and the Service Definition in each cluster. In the following command, substitute REVISION with the istiod revision label that you noted from the previous step.

    for CTX in ${CTX_1} ${CTX_2}
    do
        kubectl create --context=${CTX} namespace sample
        kubectl label --context=${CTX} namespace sample \
            istio-injection- istio.io/rev=REVISION --overwrite
    done
    

    where REVISION is the istiod revision label that you previously noted.

    The output is:

    label "istio-injection" not found.
    namespace/sample labeled
    

    You can safely ignore label "istio-injection" not found.

  2. Create the HelloWorld service in both clusters:

    kubectl create --context=${CTX_1} \
        -f ${SAMPLES_DIR}/samples/helloworld/helloworld.yaml \
        -l service=helloworld -n sample
    
    kubectl create --context=${CTX_2} \
        -f ${SAMPLES_DIR}/samples/helloworld/helloworld.yaml \
        -l service=helloworld -n sample
    

Deploy HelloWorld v1 and v2 to each cluster

  1. Deploy HelloWorld v1 to CLUSTER_1 and v2 to CLUSTER_2, which helps later to verify cross-cluster load balancing:

    kubectl create --context=${CTX_1} \
      -f ${SAMPLES_DIR}/samples/helloworld/helloworld.yaml \
      -l version=v1 -n sample
    kubectl create --context=${CTX_2} \
      -f ${SAMPLES_DIR}/samples/helloworld/helloworld.yaml \
      -l version=v2 -n sample
  2. Confirm HelloWorld v1 and v2 are running using the following commands. Verify that the output is similar to that shown.:

    kubectl get pod --context=${CTX_1} -n sample
    NAME                            READY     STATUS    RESTARTS   AGE
    helloworld-v1-86f77cd7bd-cpxhv  2/2       Running   0          40s
    kubectl get pod --context=${CTX_2} -n sample
    NAME                            READY     STATUS    RESTARTS   AGE
    helloworld-v2-758dd55874-6x4t8  2/2       Running   0          40s

Deploy the Sleep service

  1. Deploy the Sleep service to both clusters. This pod generates artificial network traffic for demonstration purposes:

    for CTX in ${CTX_1} ${CTX_2}
    do
        kubectl apply --context=${CTX} \
            -f ${SAMPLES_DIR}/samples/sleep/sleep.yaml -n sample
    done
    
  2. Wait for the Sleep service to start in each cluster. Verify that the output is similar to that shown:

    kubectl get pod --context=${CTX_1} -n sample -l app=sleep
    NAME                             READY   STATUS    RESTARTS   AGE
    sleep-754684654f-n6bzf           2/2     Running   0          5s
    kubectl get pod --context=${CTX_2} -n sample -l app=sleep
    NAME                             READY   STATUS    RESTARTS   AGE
    sleep-754684654f-dzl9j           2/2     Running   0          5s

Verify cross-cluster load balancing

Call the HelloWorld service several times and check the output to verify alternating replies from v1 and v2:

  1. Call the HelloWorld service:

    kubectl exec --context="${CTX_1}" -n sample -c sleep \
        "$(kubectl get pod --context="${CTX_1}" -n sample -l \
        app=sleep -o jsonpath='{.items[0].metadata.name}')" \
        -- curl -sS helloworld.sample:5000/hello
    

    The output is similar to that shown:

    Hello version: v2, instance: helloworld-v2-758dd55874-6x4t8
    Hello version: v1, instance: helloworld-v1-86f77cd7bd-cpxhv
    ...
  2. Call the HelloWorld service again:

    kubectl exec --context="${CTX_2}" -n sample -c sleep \
        "$(kubectl get pod --context="${CTX_2}" -n sample -l \
        app=sleep -o jsonpath='{.items[0].metadata.name}')" \
        -- curl -sS helloworld.sample:5000/hello
    

    The output is similar to that shown:

    Hello version: v2, instance: helloworld-v2-758dd55874-6x4t8
    Hello version: v1, instance: helloworld-v1-86f77cd7bd-cpxhv
    ...

Congratulations, you've verified your load-balanced, multi-cluster Anthos Service Mesh!

Clean up HelloWorld service

When you finish verifying load balancing, remove the HelloWorld and Sleep service from your cluster.

kubectl delete ns sample --context ${CTX_1}
kubectl delete ns sample --context ${CTX_2}