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Install Multiple Istio Control Planes in a Single Cluster Install multiple Istio control planes in a single cluster using revisions and discoverySelectors. 55
multiple
control
istiod
local
istio/wg-environments-maintainers yes

{{< boilerplate experimental-feature-warning >}}

This guide walks you through the process of installing multiple Istio control planes within a single cluster and then a way to scope workloads to specific control planes. This deployment model has a single Kubernetes control plane with multiple Istio control planes and meshes. The separation between the meshes is provided by Kubernetes namespaces and RBAC.

{{< image width="90%" link="single-cluster-multiple-istiods.svg" caption="Multiple meshes in a single cluster" >}}

Using discoverySelectors, you can scope Kubernetes resources in a cluster to specific namespaces managed by an Istio control plane. This includes the Istio custom resources (e.g., Gateway, VirtualService, DestinationRule, etc.) used to configure the mesh. Furthermore, discoverySelectors can be used to configure which namespaces should include the istio-ca-root-cert config map for a particular Istio control plane. Together, these functions allow mesh operators to specify the namespaces for a given control plane, enabling soft multi-tenancy for multiple meshes based on the boundary of one or more namespaces. This guide uses discoverySelectors, along with the revisions capability of Istio, to demonstrate how two meshes can be deployed on a single cluster, each working with a properly scoped subset of the cluster's resources.

Before you begin

This guide requires that you have a Kubernetes cluster with any of the supported Kubernetes versions: {{< supported_kubernetes_versions >}}.

This cluster will host two control planes installed in two different system namespaces. The mesh application workloads will run in multiple application-specific namespaces, each namespace associated with one or the other control plane based on revision and discovery selector configurations.

Cluster configuration

Deploying multiple control planes

Deploying multiple Istio control planes on a single cluster can be achieved by using different system namespaces for each control plane. Istio revisions and discoverySelectors are then used to scope the resources and workloads that are managed by each control plane. {{< warning >}} By default, Istio only uses discoverySelectors to scope workload endpoints. To enable full resource scoping, including configuration resources, the feature flag ENABLE_ENHANCED_RESOURCE_SCOPING must be set to true. {{< /warning >}}

  1. Create the first system namespace, usergroup-1, and deploy istiod in it:

    {{< text bash >}} $ kubectl create ns usergroup-1 $ kubectl label ns usergroup-1 usergroup=usergroup-1 $ istioctl install -y -f - <<EOF apiVersion: install.istio.io/v1alpha1 kind: IstioOperator metadata: namespace: usergroup-1 spec: profile: minimal revision: usergroup-1 meshConfig: discoverySelectors: - matchLabels: usergroup: usergroup-1 values: global: istioNamespace: usergroup-1 pilot: env: ENABLE_ENHANCED_RESOURCE_SCOPING: true EOF {{< /text >}}

  2. Create the second system namespace, usergroup-2, and deploy istiod in it:

    {{< text bash >}} $ kubectl create ns usergroup-2 $ kubectl label ns usergroup-2 usergroup=usergroup-2 $ istioctl install -y -f - <<EOF apiVersion: install.istio.io/v1alpha1 kind: IstioOperator metadata: namespace: usergroup-2 spec: profile: minimal revision: usergroup-2 meshConfig: discoverySelectors: - matchLabels: usergroup: usergroup-2 values: global: istioNamespace: usergroup-2 pilot: env: ENABLE_ENHANCED_RESOURCE_SCOPING: true EOF {{< /text >}}

  3. Deploy a policy for workloads in the usergroup-1 namespace to only accept mutual TLS traffic:

    {{< text bash >}} $ kubectl apply -f - <<EOF apiVersion: security.istio.io/v1beta1 kind: PeerAuthentication metadata: name: "usergroup-1-peerauth" namespace: "usergroup-1" spec: mtls: mode: STRICT EOF {{< /text >}}

  4. Deploy a policy for workloads in the usergroup-2 namespace to only accept mutual TLS traffic:

    {{< text bash >}} $ kubectl apply -f - <<EOF apiVersion: security.istio.io/v1beta1 kind: PeerAuthentication metadata: name: "usergroup-2-peerauth" namespace: "usergroup-2" spec: mtls: mode: STRICT EOF {{< /text >}}

Verify the multiple control plane creation

  1. Check the labels on the system namespaces for each control plane:

    {{< text bash >}} $ kubectl get ns usergroup-1 usergroup2 --show-labels NAME STATUS AGE LABELS usergroup-1 Active 13m kubernetes.io/metadata.name=usergroup-1,usergroup=usergroup-1 usergroup-2 Active 12m kubernetes.io/metadata.name=usergroup-2,usergroup=usergroup-2 {{< /text >}}

  2. Verify the control planes are deployed and running:

    {{< text bash >}} $ kubectl get pods -n usergroup-1 NAMESPACE NAME READY STATUS RESTARTS AGE usergroup-1 istiod-usergroup-1-5ccc849b5f-wnqd6 1/1 Running 0 12m {{< /text >}}

    {{< text bash >}} $ kubectl get pods -n usergroup-2 NAMESPACE NAME READY STATUS RESTARTS AGE usergroup-2 istiod-usergroup-2-658d6458f7-slpd9 1/1 Running 0 12m {{< /text >}}

    You will notice that one istiod deployment per usergroup is created in the specified namespaces.

  3. Run the following commands to list the installed webhooks:

    {{< text bash >}} $ kubectl get validatingwebhookconfiguration NAME WEBHOOKS AGE istio-validator-usergroup-1-usergroup-1 1 18m istio-validator-usergroup-2-usergroup-2 1 18m istiod-default-validator 1 18m {{< /text >}}

    {{< text bash >}} $ kubectl get mutatingwebhookconfiguration NAME WEBHOOKS AGE istio-revision-tag-default-usergroup-1 4 18m istio-sidecar-injector-usergroup-1-usergroup-1 2 19m istio-sidecar-injector-usergroup-2-usergroup-2 2 18m {{< /text >}}

    Note that the output includes istiod-default-validator and istio-revision-tag-default-usergroup-1, which are the default webhook configurations used for handling requests coming from resources which are not associated with any revision. In a fully scoped environment where every control plane is associated with its resources through proper namespace labeling, there is no need for these default webhook configurations. They should never be invoked.

Deploy application workloads per usergroup

  1. Create three application namespaces:

    {{< text bash >}} $ kubectl create ns app-ns-1 $ kubectl create ns app-ns-2 $ kubectl create ns app-ns-3 {{< /text >}}

  2. Label each namespace to associate them with their respective control planes:

    {{< text bash >}} $ kubectl label ns app-ns-1 usergroup=usergroup-1 istio.io/rev=usergroup-1 $ kubectl label ns app-ns-2 usergroup=usergroup-2 istio.io/rev=usergroup-2 $ kubectl label ns app-ns-3 usergroup=usergroup-2 istio.io/rev=usergroup-2 {{< /text >}}

  3. Deploy one sleep and httpbin application per namespace:

    {{< text bash >}} $ kubectl -n app-ns-1 apply -f samples/sleep/sleep.yaml $ kubectl -n app-ns-1 apply -f samples/httpbin/httpbin.yaml $ kubectl -n app-ns-2 apply -f samples/sleep/sleep.yaml $ kubectl -n app-ns-2 apply -f samples/httpbin/httpbin.yaml $ kubectl -n app-ns-3 apply -f samples/sleep/sleep.yaml $ kubectl -n app-ns-3 apply -f samples/httpbin/httpbin.yaml {{< /text >}}

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

    {{< text bash >}} $ kubectl get pods -n app-ns-1 NAME READY STATUS RESTARTS AGE httpbin-9dbd644c7-zc2v4 2/2 Running 0 115m sleep-78ff5975c6-fml7c 2/2 Running 0 115m {{< /text >}}

    {{< text bash >}} $ kubectl get pods -n app-ns-2 NAME READY STATUS RESTARTS AGE httpbin-9dbd644c7-sd9ln 2/2 Running 0 115m sleep-78ff5975c6-sz728 2/2 Running 0 115m {{< /text >}}

    {{< text bash >}} $ kubectl get pods -n app-ns-3 NAME READY STATUS RESTARTS AGE httpbin-9dbd644c7-8ll27 2/2 Running 0 115m sleep-78ff5975c6-sg4tq 2/2 Running 0 115m {{< /text >}}

Verify the application to control plane mapping

Now that the applications are deployed, you can use the istioctl ps command to confirm that the application workloads are managed by their respective control plane, i.e., app-ns-1 is managed by usergroup-1, app-ns-2 and app-ns-3 are managed by usergroup-2:

{{< text bash >}} $ istioctl ps -i usergroup-1 NAME CLUSTER CDS LDS EDS RDS ECDS ISTIOD VERSION httpbin-9dbd644c7-hccpf.app-ns-1 Kubernetes SYNCED SYNCED SYNCED SYNCED NOT SENT istiod-usergroup-1-5ccc849b5f-wnqd6 1.17-alpha.f5212a6f7df61fd8156f3585154bed2f003c4117 sleep-78ff5975c6-9zb77.app-ns-1 Kubernetes SYNCED SYNCED SYNCED SYNCED NOT SENT istiod-usergroup-1-5ccc849b5f-wnqd6 1.17-alpha.f5212a6f7df61fd8156f3585154bed2f003c4117 {{< /text >}}

{{< text bash >}} $ istioctl ps -i usergroup-2 NAME CLUSTER CDS LDS EDS RDS ECDS ISTIOD VERSION httpbin-9dbd644c7-vvcqj.app-ns-3 Kubernetes SYNCED SYNCED SYNCED SYNCED NOT SENT istiod-usergroup-2-658d6458f7-slpd9 1.17-alpha.f5212a6f7df61fd8156f3585154bed2f003c4117 httpbin-9dbd644c7-xzgfm.app-ns-2 Kubernetes SYNCED SYNCED SYNCED SYNCED NOT SENT istiod-usergroup-2-658d6458f7-slpd9 1.17-alpha.f5212a6f7df61fd8156f3585154bed2f003c4117 sleep-78ff5975c6-fthmt.app-ns-2 Kubernetes SYNCED SYNCED SYNCED SYNCED NOT SENT istiod-usergroup-2-658d6458f7-slpd9 1.17-alpha.f5212a6f7df61fd8156f3585154bed2f003c4117 sleep-78ff5975c6-nxtth.app-ns-3 Kubernetes SYNCED SYNCED SYNCED SYNCED NOT SENT istiod-usergroup-2-658d6458f7-slpd9 1.17-alpha.f5212a6f7df61fd8156f3585154bed2f003c4117 {{< /text >}}

Verify the application connectivity is ONLY within the respective usergroup

  1. Send a request from the sleep pod in app-ns-1 in usergroup-1 to the httpbin service in app-ns-2 in usergroup-2. The communication should fail:

    {{< text bash >}} kubectl -n app-ns-1 exec "(kubectl -n app-ns-1 get pod -l app=sleep -o jsonpath={.items..metadata.name})" -c sleep -- curl -sIL http://httpbin.app-ns-2.svc.cluster.local:8000 HTTP/1.1 503 Service Unavailable content-length: 95 content-type: text/plain date: Sat, 24 Dec 2022 06:54:54 GMT server: envoy {{< /text >}}

  2. Send a request from the sleep pod in app-ns-2 in usergroup-2 to the httpbin service in app-ns-3 in usergroup-2. The communication should work:

    {{< text bash >}} kubectl -n app-ns-2 exec "(kubectl -n app-ns-2 get pod -l app=sleep -o jsonpath={.items..metadata.name})" -c sleep -- curl -sIL http://httpbin.app-ns-3.svc.cluster.local:8000 HTTP/1.1 200 OK server: envoy date: Thu, 22 Dec 2022 15:01:36 GMT content-type: text/html; charset=utf-8 content-length: 9593 access-control-allow-origin: * access-control-allow-credentials: true x-envoy-upstream-service-time: 3 {{< /text >}}

Cleanup

  1. Clean up the first usergroup:

    {{< text bash >}} $ istioctl uninstall --revision usergroup-1 $ kubectl delete ns app-ns-1 usergroup-1 {{< /text >}}

  2. Clean up the second usergroup:

    {{< text bash >}} $ istioctl uninstall --revision usergroup-2 $ kubectl delete ns app-ns-2 app-ns-3 usergroup-2 {{< /text >}}

{{< warning >}} A Cluster Administrator must make sure that Mesh Administrators DO NOT have permission to invoke the global istioctl uninstall --purge command, because that would uninstall all control planes in the cluster. {{< /warning >}}