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Multi Tenant Operator in Amazon Elastic Kubernetes Service#

This document covers how to link Multi Tenant Operator with an Amazon EKS (Elastic Kubernetes Service) cluster.

Prerequisites#

  • You need kubectl as well, with a minimum version of 1.18.3. If you need to install, see Install kubectl.
  • To install MTO, you need Helm CLI as well. Visit Installing Helm to get Helm CLI
  • You need to have a user in AWS Console, which we will use as the administrator having enough permissions for accessing the cluster and creating groups with users
  • A running EKS Cluster. Creating an EKS Cluster provides a good tutorial to create a demo cluster

Setting up an EKS Cluster#

In this example, we have already set-up a small EKS cluster with the following node group specifications

Node Group

We have access configuration set as both, EKS API and Configmap, so that admin can access the cluster using EKS API and map IAM users to our EKS cluster using aws-auth configmap.

EKS Access Config

And we have a policy AmazonEKSClusterAdminPolicy attached with our user which makes it a cluster admin. To be noted, the user is also added in the cluster-admins group which we will later use while installing MTO.

EKS Access Entry

Installing Cert Manager and MTO#

We, as cluster admins, will start by installing cert manager for automated handling of operator certs.

kubectl apply -f https://github.com/cert-manager/cert-manager/releases/download/v1.14.4/cert-manager.yaml

Let's wait for the pods to be up.

NAME                                       READY   STATUS    RESTARTS   AGE
cert-manager-7fb948f468-wgcbx              1/1     Running   0          7m18s
cert-manager-cainjector-75c5fc965c-wxtkp   1/1     Running   0          7m18s
cert-manager-webhook-757c9d4bb7-wd9g8      1/1     Running   0          7m18s

We will be using helm to install the operator, here we have set bypassedGroups as cluster-admins because our admin user is part of that group as seen in above screenshot.

helm install tenant-operator oci://ghcr.io/stakater/public/charts/multi-tenant-operator --version 0.12.62 --namespace multi-tenant-operator --create-namespace --set bypassedGroups=cluster-admins

We will wait for the pods to come in running state.

NAME                                                              READY   STATUS    RESTARTS   AGE
tenant-operator-namespace-controller-768f9459c4-758kb             2/2     Running   0          5m
tenant-operator-pilot-controller-7c96f6589c-d979f                 2/2     Running   0          5m
tenant-operator-resourcesupervisor-controller-566f59d57b-xbkws    2/2     Running   0          5m
tenant-operator-template-quota-intconfig-controller-7fc99462dz6   2/2     Running   0          5m
tenant-operator-templategroupinstance-controller-75cf68c872pljv   2/2     Running   0          5m
tenant-operator-templateinstance-controller-d996b6fd-cx2dz        2/2     Running   0          5m
tenant-operator-tenant-controller-57fb885c84-7ps92                2/2     Running   0          5m
tenant-operator-webhook-5f8f675549-jv9n8                          2/2     Running   0          5m

Users Interaction with the Cluster#

We will use two types of users to interact with the cluster, IAM users created via AWS Console and SSO Users.

IAM Users#

We have created a user named test-benzema-mto in AWS Console, with ARN arn:aws:iam::<account>:user/test-benzema-mto. This user has a policy attached to be able to get cluster info

{
    "Statement": [
        {
            "Action": "eks:DescribeCluster",
            "Effect": "Allow",
            "Resource": "*"
        }
    ],
    "Version": "2012-10-17"
}

We have mapped this user in aws-auth configmap in kube-system namespace.

  mapUsers:
    - groups:
      - iam-devteam
      userarn: arn:aws:iam::<account>:user/test-benzema-mto
      username: test-benzema-mto

Using this AWS guide, we will ask the user to update its kubeconfig and try to access the cluster.

Since we haven't attached any RBAC with this user at the moment, trying to access anything in the cluster would throw an error

$ kubectl get svc

Error from server (Forbidden): services is forbidden: User "test-benzema-mto" cannot list resource "services" in API group "" in the namespace "default"

SSO Users#

For SSO Users, we will map a role arn:aws:iam::<account>:role/aws-reserved/sso.amazonaws.com/eu-north-1/AWSReservedSSO_PowerUserAccess_b0ad9936c75e5bcc, that is attached by default with Users on SSO login to the AWS console and awscli, in aws-auth configmap in kube-system namespace.

  mapRoles:
    - groups:
      - sso-devteam
      rolearn: arn:aws:iam::<account>:role/AWSReservedSSO_PowerUserAccess_b0ad9936c75e5bcc
      username: sso-devteam:{{SessionName}}

Since this user also doesn't have attached RBAC, trying to access anything in the cluster would throw an error

$ kubectl get svc

Error from server (Forbidden): services is forbidden: User "sso-devteam:random-user-stakater.com" cannot list resource "services" in API group "" in the namespace "default"

Setting up Tenant for Users#

Now, we will set tenants for the above-mentioned users.

We will start by creating a Quota CR with some resource limits

kubectl apply -f - <<EOF
apiVersion: tenantoperator.stakater.com/v1beta1
kind: Quota
metadata:
  name: small
spec:
  limitrange:
    limits:
    - max:
        cpu: 800m
      min:
        cpu: 200m
      type: Container
  resourcequota:
    hard:
      configmaps: "10"
      memory: "8Gi"
EOF

Now, we will mention this Quota in two Tenant CRs

kubectl apply -f - <<EOF
apiVersion: tenantoperator.stakater.com/v1beta3
kind: Tenant
metadata:
  name: tenant-iam
spec:
  namespaces:
    withTenantPrefix:
    - dev
    - build
  accessControl:
    owners:
      groups:
      - iam-devteam
  quota: small
EOF

kubectl apply -f - <<EOF
apiVersion: tenantoperator.stakater.com/v1beta3
kind: Tenant
metadata:
  name: tenant-sso
spec:
  namespaces:
    withTenantPrefix:
    - dev
    - build
  accessControl:
    owners:
      groups:
    - sso-devteam
  quota: small
EOF

Notice that the only difference in both tenant specs are the groups.

Accessing Tenant Namespaces#

After the creation of Tenant CRs, now users can access namespaces in their respective tenants and preform create, update, delete functions.

Listing the namespaces by cluster admin will show us the recently created tenant namespaces

$ kubectl get namespaces

NAME                    STATUS   AGE
cert-manager            Active   8d
default                 Active   9d
kube-node-lease         Active   9d
kube-public             Active   9d
kube-system             Active   9d
multi-tenant-operator   Active   8d
random                  Active   8d
tenant-iam-build        Active   5s
tenant-iam-dev          Active   5s
tenant-sso-build        Active   5s
tenant-sso-dev          Active   5s

IAM Users on Tenant Namespaces#

We will now try to deploy a pod from user test-benzema-mto in its tenant namespace tenant-iam-dev

$ kubectl run nginx --image nginx -n tenant-iam-dev

pod/nginx created

And if we try the same operation in the other tenant with the same user, it will fail

$ kubectl run nginx --image nginx -n tenant-sso-dev

Error from server (Forbidden): pods is forbidden: User "test-benzema-mto" cannot create resource "pods" in API group "" in the namespace "tenant-sso-dev"

To be noted, test-benzema-mto can not list namespaces

$ kubectl get namespaces

Error from server (Forbidden): namespaces is forbidden: User "test-benzema-mto" cannot list resource "namespaces" in API group "" at the cluster scope

SSO Users on Tenant Namespaces#

We will repeat the above operations for our SSO user sso-devteam:random-user-stakater.com as well

$ kubectl run nginx --image nginx -n tenant-sso-dev

pod/nginx created

Trying to do operations outside the scope of its own tenant will result in errors

$ kubectl run nginx --image nginx -n tenant-iam-dev

Error from server (Forbidden): pods is forbidden: User "sso-devteam:random-user-stakater.com" cannot create resource "pods" in API group "" in the namespace "tenant-iam-dev"

To be noted, sso-devteam:random-user-stakater.com can not list namespaces

$ kubectl get namespaces

Error from server (Forbidden): namespaces is forbidden: User "sso-devteam:random-user-stakater.com" cannot list resource "namespaces" in API group "" at the cluster scope