Install Istio with an External Control Plane

    External control plane cluster and remote cluster

    Envoy proxies (sidecars and gateways) running in the remote cluster access the external istiod via an ingress gateway which exposes the endpoints needed for discovery, CA, injection, and validation.

    While configuration and management of the external control plane is done by the mesh operator in the external cluster, the first remote cluster connected to an external control plane serves as the config cluster for the mesh itself. The mesh administrator will use the config cluster to configure the mesh resources (gateways, virtual services, etc.) in addition to the mesh services themselves. The external control plane will remotely access this configuration from the Kubernetes API server, as shown in the above diagram.

    This guide requires that you have two Kubernetes clusters with any of the supported Kubernetes versions: 1.18, 1.19, 1.20, 1.21.

    The first cluster will host the external control plane installed in the namespace. An ingress gateway is also installed in the istio-system namespace to provide cross-cluster access to the external control plane.

    The second cluster is a remote cluster that will run the mesh application workloads. Its Kubernetes API server also provides the mesh configuration used by the external control plane (istiod) to configure the workload proxies.

    API server access

    The Kubernetes API server in the remote cluster must be accessible to the external control plane cluster. Many cloud providers make API servers publicly accessible via network load balancers (NLBs). If the API server is not directly accessible, you will need to modify the installation procedure to enable access. For example, the east-west gateway used in a could also be used to enable access to the API server.

    The following environment variables will be used throughout to simplify the instructions:

    Set the CTX_EXTERNAL_CLUSTER, CTX_REMOTE_CLUSTER, and REMOTE_CLUSTER_NAME now. You will set the others later.

    Mesh operator steps

    A mesh operator is responsible for installing and managing the external Istio control plane on the external cluster. This includes configuring an ingress gateway on the external cluster, which allows the remote cluster to access the control plane, and installing the sidecar injector webhook configuration on the remote cluster so that it will use the external control plane.

    Set up a gateway in the external cluster

    1. Create the Istio install configuration for the ingress gateway that will expose the external control plane ports to other clusters:

      1. $ cat <<EOF > controlplane-gateway.yaml
      2. apiVersion: install.istio.io/v1alpha1
      3. kind: IstioOperator
      4. metadata:
      5.   namespace: istio-system
      6. spec:
      7.   components:
      8.     ingressGateways:
      9.       - name: istio-ingressgateway
      10.         enabled: true
      11.         k8s:
      12.           service:
      13.             ports:
      14.               - port: 15021
      15.                 targetPort: 15021
      16.                 name: status-port
      17.               - port: 15012
      18.                 targetPort: 15012
      19.                 name: tls-xds
      20.               - port: 15017
      21.                 targetPort: 15017
      22.                 name: tls-webhook
      23. EOF

      Then, install the gateway in the istio-system namespace of the external cluster:

      1. $ istioctl install -f controlplane-gateway.yaml --context="${CTX_EXTERNAL_CLUSTER}"

    2. Run the following command to confirm that the ingress gateway is up and running:

      1. $ kubectl get po -n istio-system --context="${CTX_EXTERNAL_CLUSTER}"
      2. NAME                                   READY   STATUS    RESTARTS   AGE
      3. istio-ingressgateway-9d4c7f5c7-7qpzz   1/1     Running   0          29s
      4. istiod-68488cd797-mq8dn                1/1     Running   0          38s

      You will notice an istiod deployment is also created in the istio-system namespace. This is used to configure the ingress gateway and is NOT the control plane used by remote clusters.

      This ingress gateway could be configured to host multiple external control planes, in different namespaces on the external cluster, although in this example you will only deploy a single external istiod in the external-istiod namespace.

    3. Configure your environment to expose the Istio ingress gateway service using a public hostname with TLS. Set the EXTERNAL_ISTIOD_ADDR environment variable to the hostname and SSL_SECRET_NAME environment variable to the secret that holds the TLS certs:

      1. $ export EXTERNAL_ISTIOD_ADDR=<your external istiod host>
      2. $ export SSL_SECRET_NAME=<your external istiod secret>

    Set up the remote config cluster

    1. Create the remote cluster’s Istio install configuration, which installs the injection webhook that uses the external control plane’s injector, instead of a locally deployed one. Because this cluster also serves as the config cluster, the Istio CRDs and istio configmap (i.e., global mesh config) are also installed by setting base.enabled and pilot.configMap to true:

      1. $ cat <<EOF > remote-config-cluster.yaml
      2. apiVersion: install.istio.io/v1alpha1
      3. kind: IstioOperator
      4. metadata:
      5.   namespace: external-istiod
      6. spec:
      7.   profile: external
      8.   components:
      9.     base:
      10.       enabled: true
      11.   values:
      12.     global:
      13.       istioNamespace: external-istiod
      14.     pilot:
      15.       configMap: true
      16.     istiodRemote:
      17.       injectionURL: https://${EXTERNAL_ISTIOD_ADDR}:15017/inject/:ENV:cluster=${REMOTE_CLUSTER_NAME}:ENV:net=network1
      18.     base:
      19.       validationURL: https://${EXTERNAL_ISTIOD_ADDR}:15017/validate
      20. EOF

      Then, install the configuration on the remote cluster:

      1. $ kubectl create namespace external-istiod --context="${CTX_REMOTE_CLUSTER}"
      2. $ istioctl manifest generate -f remote-config-cluster.yaml | kubectl apply --context="${CTX_REMOTE_CLUSTER}" -f -

    2. Confirm that the remote cluster’s webhook configuration has been installed:

      1. $ kubectl get mutatingwebhookconfiguration -n external-istiod --context="${CTX_REMOTE_CLUSTER}"
      2. NAME                                     WEBHOOKS   AGE
      3. istio-sidecar-injector-external-istiod   4          6m24s

    Set up the control plane in the external cluster

    1. Create the external-istiod namespace, which will be used to host the external control plane:

      1. $ kubectl create namespace external-istiod --context="${CTX_EXTERNAL_CLUSTER}"
      1. $ kubectl create sa istiod-service-account -n external-istiod --context="${CTX_EXTERNAL_CLUSTER}"
      2. $ istioctl x create-remote-secret \
      3.   --context="${CTX_REMOTE_CLUSTER}" \
      4.   --type=config \
      5.   --namespace=external-istiod | \
      6.   kubectl apply -f - --context="${CTX_EXTERNAL_CLUSTER}"

    3. Create the Istio configuration to install the control plane in the external-istiod namespace of the external cluster. Notice that istiod is configured to use the locally mounted istio configmap and the SHARED_MESH_CONFIG environment variable is set to istio. This instructs istiod to merge the values set by the mesh admin in the config cluster’s configmap with the values in the local configmap set by the mesh operator, here, which will take precedence if there are any conflicts:

      1. $ cat <<EOF > external-istiod.yaml
      2. apiVersion: install.istio.io/v1alpha1
      3. kind: IstioOperator
      4. metadata:
      5.   namespace: external-istiod
      6. spec:
      7.   profile: empty
      8.     rootNamespace: external-istiod
      10.       discoveryAddress: $EXTERNAL_ISTIOD_ADDR:15012
      11.       proxyMetadata:
      12.         XDS_ROOT_CA: /etc/ssl/certs/ca-certificates.crt
      13.         CA_ROOT_CA: /etc/ssl/certs/ca-certificates.crt
      14.   components:
      15.     pilot:
      16.       enabled: true
      17.       k8s:
      18.         overlays:
      19.         - kind: Deployment
      20.           name: istiod
      21.           patches:
      22.           - path: spec.template.spec.volumes[100]
      23.             value: |-
      24.               name: config-volume
      25.               configMap:
      26.                 name: istio
      27.           - path: spec.template.spec.volumes[100]
      28.             value: |-
      29.               name: inject-volume
      30.               configMap:
      31.                 name: istio-sidecar-injector
      32.           - path: spec.template.spec.containers[0].volumeMounts[100]
      33.             value: |-
      34.               name: config-volume
      35.               mountPath: /etc/istio/config
      36.           - path: spec.template.spec.containers[0].volumeMounts[100]
      37.             value: |-
      38.               name: inject-volume
      39.               mountPath: /var/lib/istio/inject
      40.         env:
      41.         - name: INJECTION_WEBHOOK_CONFIG_NAME
      42.           value: ""
      43.         - name: VALIDATION_WEBHOOK_CONFIG_NAME
      44.           value: ""
      45.         - name: EXTERNAL_ISTIOD
      46.           value: "true"
      47.         - name: CLUSTER_ID
      48.           value: ${REMOTE_CLUSTER_NAME}
      49.         - name: SHARED_MESH_CONFIG
      50.           value: istio
      51.   values:
      52.     global:
      53.       caAddress: $EXTERNAL_ISTIOD_ADDR:15012
      54.       istioNamespace: external-istiod
      55.       operatorManageWebhooks: true
      56.       meshID: mesh1
      57. EOF

      Then, apply the Istio configuration on the external cluster:

      1. $ istioctl install -f external-istiod.yaml --context="${CTX_EXTERNAL_CLUSTER}"

    4. Confirm that the external istiod has been successfully deployed:

      1. $ kubectl get po -n external-istiod --context="${CTX_EXTERNAL_CLUSTER}"
      2. NAME                      READY   STATUS    RESTARTS   AGE
      3. istiod-779bd6fdcf-bd6rg   1/1     Running   0          70s

    5. Create the Istio Gateway, VirtualService, and DestinationRule configuration to route traffic from the ingress gateway to the external control plane:

      Then, apply the configuration on the external cluster:

      1. $ kubectl apply -f external-istiod-gw.yaml --context="${CTX_EXTERNAL_CLUSTER}"

    Now that Istio is up and running, a mesh administrator only needs to deploy and configure services in the mesh, including gateways, if needed.

    Deploy a sample application

    1. Create, and label for injection, the sample namespace on the remote cluster:

      1. $ kubectl create --context="${CTX_REMOTE_CLUSTER}" namespace sample
      2. $ kubectl label --context="${CTX_REMOTE_CLUSTER}" namespace sample istio-injection=enabled

    2. Deploy the helloworld (v1) and sleep samples:

      ZipZip

      1. $ kubectl apply -f @samples/helloworld/helloworld.yaml@ -l service=helloworld -n sample --context="${CTX_REMOTE_CLUSTER}"
      2. $ kubectl apply -f @samples/helloworld/helloworld.yaml@ -l version=v1 -n sample --context="${CTX_REMOTE_CLUSTER}"
      3. $ kubectl apply -f @samples/sleep/sleep.yaml@ -n sample --context="${CTX_REMOTE_CLUSTER}"

    3. Wait a few seconds for the helloworld and sleep pods to be running with sidecars injected:

      1. $ kubectl get pod -n sample --context="${CTX_REMOTE_CLUSTER}"
      2. NAME                             READY   STATUS    RESTARTS   AGE
      3. helloworld-v1-776f57d5f6-s7zfc   2/2     Running   0          10s
      4. sleep-64d7d56698-wqjnm           2/2     Running   0          9s

    4. Send a request from the sleep pod to the helloworld service:

      1. $ kubectl exec --context="${CTX_REMOTE_CLUSTER}" -n sample -c sleep \
      2.     "$(kubectl get pod --context="${CTX_REMOTE_CLUSTER}" -n sample -l app=sleep -o jsonpath='{.items[0].metadata.name}')" \
      3.     -- curl -sS helloworld.sample:5000/hello
      4. Hello version: v1, instance: helloworld-v1-776f57d5f6-s7zfc

    Enable gateways

    1. Enable an ingress gateway on the remote cluster:

      1. $ cat <<EOF > istio-ingressgateway.yaml
      2. apiVersion: operator.istio.io/v1alpha1
      3. kind: IstioOperator
      4. spec:
      5.   profile: empty
      6.   components:
      7.     ingressGateways:
      8.     - namespace: external-istiod
      9.       name: istio-ingressgateway
      10.       enabled: true
      11.   values:
      12.     gateways:
      13.       istio-ingressgateway:
      14.         injectionTemplate: gateway
      15. EOF
      16. $ istioctl install -f istio-ingressgateway.yaml --context="${CTX_REMOTE_CLUSTER}"

    2. Enable an egress gateway, or other gateways, on the remote cluster (optional):

      1. $ cat <<EOF > istio-egressgateway.yaml
      3. spec:
      4.   profile: empty
      5.   components:
      6.     egressGateways:
      7.     - namespace: external-istiod
      8.       name: istio-egressgateway
      9.       enabled: true
      10.   values:
      11.     gateways:
      12.       istio-egressgateway:
      13.         injectionTemplate: gateway
      14. EOF
      15. $ istioctl install -f istio-egressgateway.yaml --context="${CTX_REMOTE_CLUSTER}"

    3. Confirm that the Istio ingress gateway is running:

      1. $ kubectl get pod -l app=istio-ingressgateway -n external-istiod --context="${CTX_REMOTE_CLUSTER}"
      2. NAME                                    READY   STATUS    RESTARTS   AGE
      3. istio-ingressgateway-7bcd5c6bbd-kmtl4   1/1     Running   0          8m4s

    4. Expose the helloworld application on the ingress gateway:

      1. $ kubectl apply -f @samples/helloworld/helloworld-gateway.yaml@ -n sample --context="${CTX_REMOTE_CLUSTER}"

    5. Set the GATEWAY_URL environment variable (see determining the ingress IP and ports for details):

      1. $ export INGRESS_HOST=$(kubectl -n external-istiod --context="${CTX_REMOTE_CLUSTER}" get service istio-ingressgateway -o jsonpath='{.status.loadBalancer.ingress[0].ip}')
      2. $ export INGRESS_PORT=$(kubectl -n external-istiod --context="${CTX_REMOTE_CLUSTER}" get service istio-ingressgateway -o jsonpath='{.spec.ports[?(@.name=="http2")].port}')
      3. $ export GATEWAY_URL=$INGRESS_HOST:$INGRESS_PORT

    6. Confirm you can access the helloworld application through the ingress gateway:

      1. $ curl -s "http://${GATEWAY_URL}/hello"
      2. Hello version: v1, instance: helloworld-v1-776f57d5f6-s7zfc

    This feature is actively in development and is considered .

    This section shows you how to expand an existing external control plane mesh to multicluster by adding another remote cluster. This allows you to easily distribute services and use location-aware routing and fail over to support high availability of your application.

    Unlike the first remote cluster, the second and subsequent clusters added to the same external control plane do not provide mesh config, but instead are only sources of endpoint configuration, just like remote clusters in a primary-remote Istio multicluster configuration.

    To proceed, you’ll need another Kubernetes cluster for the second remote cluster of the mesh. Set the following environment variables to the context name and cluster name of the cluster:

    1. $ export CTX_SECOND_CLUSTER=<your second remote cluster context>
    2. $ export SECOND_CLUSTER_NAME=<your second remote cluster name>

    Register the new cluster

    1. Create a secret with credentials to allow the control plane to access the endpoints on the second remote cluster and install it:

      Note that unlike the first remote cluster of the mesh, which also serves as the config cluster, the --type argument is set to remote this time, instead of config.

      Note that the new secret can be applied in either the remote (config) cluster or in the external cluster, because the external istiod is watching for additions in both clusters.

    2. Create the remote Istio install configuration, which installs the injection webhook that uses the external control plane’s injector, instead of a locally deployed one:

      1. $ cat <<EOF > second-config-cluster.yaml
      2. apiVersion: install.istio.io/v1alpha1
      3. kind: IstioOperator
      4. metadata:
      5.   namespace: external-istiod
      6. spec:
      7.   profile: external
      8.   values:
      9.     global:
      10.       istioNamespace: external-istiod
      11.     istiodRemote:
      12.       injectionURL: https://${EXTERNAL_ISTIOD_ADDR}:15017/inject/:ENV:cluster=${SECOND_CLUSTER_NAME}:ENV:net=network2
      13. EOF

      Then, install the configuration on the remote cluster:

      1. $ istioctl manifest generate -f second-config-cluster.yaml | kubectl apply --context="${CTX_SECOND_CLUSTER}" -f -

    3. Confirm that the remote cluster’s webhook configuration has been installed:

      1. $ kubectl get mutatingwebhookconfiguration -n external-istiod --context="${CTX_SECOND_CLUSTER}"
      2. NAME                                     WEBHOOKS   AGE
      3. istio-sidecar-injector-external-istiod   4          4m13s

    1. Deploy east-west gateways on both remote clusters:

      1. $ @samples/multicluster/gen-eastwest-gateway.sh@ \
      2.     --mesh mesh1 --cluster "${REMOTE_CLUSTER_NAME}" --network network1 > eastwest-gateway-1.yaml
      3. $ istioctl manifest generate -f eastwest-gateway-1.yaml \
      4.     --set values.gateways.istio-ingressgateway.injectionTemplate=gateway \
      5.     --set values.global.istioNamespace=external-istiod | \
      6.     kubectl apply --context="${CTX_REMOTE_CLUSTER}" -f -

      Zip

      1. $ @samples/multicluster/gen-eastwest-gateway.sh@ \
      2.     --mesh mesh1 --cluster "${SECOND_CLUSTER_NAME}" --network network2 > eastwest-gateway-2.yaml
      3. $ istioctl manifest generate -f eastwest-gateway-2.yaml \
      4.     --set values.gateways.istio-ingressgateway.injectionTemplate=gateway \
      5.     --set values.global.istioNamespace=external-istiod | \
      6.     kubectl apply --context="${CTX_SECOND_CLUSTER}" -f -

    2. Wait for the east-west gateways to be assigned external IP addresses:

      1. $ kubectl --context="${CTX_REMOTE_CLUSTER}" get svc istio-eastwestgateway -n external-istiod
      2. NAME                    TYPE           CLUSTER-IP    EXTERNAL-IP    PORT(S)   AGE
      3. istio-eastwestgateway   LoadBalancer   10.0.12.121   34.122.91.98   ...       51s
      1. $ kubectl --context="${CTX_SECOND_CLUSTER}" get svc istio-eastwestgateway -n external-istiod
      2. NAME                    TYPE           CLUSTER-IP    EXTERNAL-IP    PORT(S)   AGE
      3. istio-eastwestgateway   LoadBalancer   10.0.12.121   34.122.91.99   ...       51s

    3. Expose services via the east-west gateways:

      1. $ kubectl --context="${CTX_REMOTE_CLUSTER}" apply -n external-istiod -f \
      2.     @samples/multicluster/expose-services.yaml@

      Zip

      1. $ kubectl --context="${CTX_SECOND_CLUSTER}" apply -n external-istiod -f \
      2.     @samples/multicluster/expose-services.yaml@

    Validate the installation

    1. Create, and label for injection, the sample namespace on the remote cluster:

      1. $ kubectl create --context="${CTX_SECOND_CLUSTER}" namespace sample
      2. $ kubectl label --context="${CTX_SECOND_CLUSTER}" namespace sample istio-injection=enabled

    2. Deploy the helloworld (v2) and sleep samples:

      Zip

      1. $ kubectl apply -f @samples/helloworld/helloworld.yaml@ -l service=helloworld -n sample --context="${CTX_SECOND_CLUSTER}"
      2. $ kubectl apply -f @samples/helloworld/helloworld.yaml@ -l version=v2 -n sample --context="${CTX_SECOND_CLUSTER}"
      3. $ kubectl apply -f @samples/sleep/sleep.yaml@ -n sample --context="${CTX_SECOND_CLUSTER}"

    3. Wait a few seconds for the helloworld and sleep pods to be running with sidecars injected:

      1. $ kubectl get pod -n sample --context="${CTX_SECOND_CLUSTER}"
      2. NAME                            READY   STATUS    RESTARTS   AGE
      3. helloworld-v2-54df5f84b-9hxgw   2/2     Running   0          10s
      4. sleep-557747455f-wtdbr          2/2     Running   0          9s

    4. Send a request from the sleep pod to the helloworld service:

    5. Confirm that when accessing the helloworld application several times through the ingress gateway, both version v1 and v2 are now being called:

      1. $ for i in {1..10}; do curl -s "http://${GATEWAY_URL}/hello"; done
      2. Hello version: v1, instance: helloworld-v1-776f57d5f6-s7zfc
      3. Hello version: v2, instance: helloworld-v2-54df5f84b-9hxgw
      4. Hello version: v1, instance: helloworld-v1-776f57d5f6-s7zfc
      5. Hello version: v2, instance: helloworld-v2-54df5f84b-9hxgw