Amazon EKS Concepts

Internal

• Amazon Elastic Kubernetes Service

EKS Cluster

Worker Node Group

A worker node group is a named EKS management entity that facilitates creation and management of EC2 instance-based Kubernetes worker nodes. There could be managed node groups and self-managed node groups. When the EKS cluster is created, the operator has the option to create on or more node groups. The node groups created this way are managed node groups. An EKS cluster can use more than one node group.

Managed Node Group

https://docs.aws.amazon.com/eks/latest/userguide/managed-node-groups.html

Managed node groups are worker node groups created by default during the provisioning of an EKs cluster.

The main characteristic of a managed node group is that it abstracts out the creation and management of individual EC2 instances. The user does not need to concern themselves with creation of individual EC2 VMs, but only indicate the type and how many are needed. The EC2 instances created by a managed node group are based on EKS-optimized AMIs. When the nodes are updated or terminated, the pods running on them are gracefully drained, in such a way to ensure that the applications stay available. The updates respect the pod disruption budgets.

Each managed node group has a one-to-one association with an EC2 Auto-Scaling group, and all nodes provisioned by the group are automatically made part of the EC2 Auto-Scaling group, so the nodes managed by a group can autoscale: the nodes launched as part of a group are automatically tagged for auto-discovery by the Kuberenetes Cluster Autoscaler. The associated auto-scaling group name can be retrieved from the managed group configuration.

The nodes managed by a group can run across multiple availability zones.

The node group can be used to apply Kubernetes labels to nodes.

When a managed node group is created, the subnets to attach nodes to must be specified. Managed nodes can be launched both in public and private subnets.

When the managed node group is created, a capacity type, which could be either On-Demand or Spot, must be selected.

Self-Managed Node Group

Contains self-managed worker nodes. The node group name can be used later to identity the Auto Scaling node group that is created for these worker nodes.

Node Group Operations

• Create a node group
• Scale up the node group

Autoscaling

Autoscaling is implemented in EKS using node groups, which in turn use EC2 auto scaling groups. The node groups can be created and associated with the EKS instance via the AWS console, when the EKS instance is created.

If you are running a stateful application across multiple availability zones that is backed by EBS volumes and using the cluster autoscaler, you should configure multiple node groups, each scoped to a single availability zone, and you should enable the --balance-simiar-node-groups feature.

Cluster Autoscaler

Kubernetes Cluster Autoscaler

Horizontal Pod Autoscaler

Kubernetes Horizontal Pod Autoscaling

Vertical Pod Autoscaler

Vertical Pod Autoscaling

Cluster Service Role

The cluster service role allows the Kubernetes control plane to manage AWS resources. The cluster service role is different from the role needed to manage computes nodes, which can be created independently. It contains an "AmazonEKSClusterPolicy" policy. The cluster service role is needed when creating the EKS cluster.

Creation procedure:

Create the Cluster Service Role

Cluster Compute Role

https://docs.aws.amazon.com/eks/latest/userguide/create-node-role.html

The compute role is an IAM role compute nodes use to operate under. It can be determined from the AWS console by going to EC2, then to a specific node, then looking up "IAM Role" for that node. Also if node groups are used, the IAM role is associated with the node group.

AWS Infrastructure Requirements

TODO: Topology diagram

Security Groups

See EKS Security Groups below.

EKS Platform Versions and Kubernetes Versions

Amazon EKS platform version.

SLA

https://aws.amazon.com/eks/sla/

aws-iam-authenticator

Page 17.

aws-iam-authenticator Operations

aws-iam-authenticator

.kube/config Configuration

AWS documentation refers to the Kubernetes configuration file as "kubeconfig".

.kube/config

EKS Security

API Server User Management and Access Control

When an EKS cluster is created, the IAM entity (user or role) that creates the cluster is automatically granted "system:master" permissions in the cluster's RBAC configuration. Where?. Additional IAM users and roles can be added after cluster creation by editing the aws-auth ConfigMap. For more details on how kubectl picks up the caller identity, see Connect to an EKS Cluster with kubectl.

aws-auth ConfigMap

The "aws-auth" ConfigMap is initially created to allow the nodes to join the cluster. It is created only after the cluster is configured with nodes.

kubectl -n kube-system -o yaml get cm aws-auth

apiVersion: v1
kind: ConfigMap
metadata:
  name: aws-auth
  namespace: kube-system
data:
  mapRoles: |
    - groups:
      - system:bootstrappers
      - system:nodes
      rolearn: arn:aws:iam::999999999999:role/playground-eks-compute-role
      username: system:node:{{EC2PrivateDNSName}}

However, the same ConfigMap can be used used to add RBAC access to IAM users and roles, as described below:

• Add individual user access.
• Add role access.

IAM Role

See Cluster Service Role.

EKS IAM Permissions

These are technically "actions", but they are commonly referred to as "permissions", which implies that the action is part of a formal permission construct associated with the entity requiring it.

• eks:DescribeCluster

Pod Security Policy

https://docs.aws.amazon.com/eks/latest/userguide/pod-security-policy.html

Also see:

Pod Security Policy Concepts

By default, the PodSecurityPolicy admission controller is enabled, but a fully permissive security policy with no restrictions, named "eks.privileged" is applied. The permission to "use" "eks.privileged" is imparted by the "eks:podsecuritypolicy:privileged" ClusterRole:

apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: eks:podsecuritypolicy:privileged
rules:
- apiGroups:
  - policy
  resourceNames:
  - eks.privileged
  resources:
  - podsecuritypolicies
  verbs:
  - use

The "eks:podsecuritypolicy:privileged" ClusterRole is bound by the "eks:podsecuritypolicy:authenticated" ClusterRoleBinding to all members of the "system:authenticated" Group, which results in the fact that any authenticated identity can use it.

Bearer Tokens

Webhook Token Authentication

EKS supports natively bearer tokens via webhook token authentication. For more details see:

EKS Webhook Token Authentication

EKS Security Groups

https://docs.aws.amazon.com/eks/latest/userguide/sec-group-reqs.html

These are the security groups to apply to the EKS-managed Elastic Network Interfaces that are created in the worker subnets.

Use the security group created by the CloudFormation stack <cluster-name>-*-ControlPlaneSecurityGroup-*

If reusing infrastructure from an existing EKS cluster, get them from Networking → Cluster Security Group

Cluster Security Group

The cluster security group is ?.

The cluster security group is automatically created during the EKS cluster creation process, and its name is similar to "eks-cluster-sg-<cluster-name>-1234". For an existing cluster, the cluster security group can be retrieved by navigating to the cluster page in AWS console, then Configuration → Networking → Cluster Security Group, or by executing:

aws eks describe-cluster --name <cluster-name> --query cluster.resourcesVpcConfig.clusterSecurityGroupId

The cluster security group is automatically updated with NLB-generated access rules.

Additional Security Groups

The additional security groups can be retrieved by navigating to the cluster page in AWS console, then Configuration → Networking → Additional Security Groups.

EKS Security Groups Operations

• Assing security groups during EKS cluster creation with AWS Console.

Load Balancing and Ingress

https://docs.aws.amazon.com/eks/latest/userguide/load-balancing-and-ingress.html

Using an Ingress

Kubernetes Ingress Concepts

Using a NLB

TODO: https://kubernetes.io/docs/concepts/services-networking/service/#aws-nlb-support

TODO: https://kubernetes.io/docs/concepts/cluster-administration/cloud-providers/#aws

metadata:
  name: my-service
  annotations:
    service.beta.kubernetes.io/aws-load-balancer-type: 'nlb'
    service.beta.kubernetes.io/aws-load-balancer-security-groups: 'sg-00000000000000000'
    service.beta.kubernetes.io/aws-load-balancer-ssl-cert: 'arn:aws:acm:xx-xxxx-x:xxxxxxxxx:xxxxxxx/xxxxx-xxxx-xxxx-xxxx-xxxxxxxxx'

Also see:

Kubernetes Service Concepts

Idiosyncrasies

It seems that a LoadBalancer deployment causes updating Kubernetes nodes' security group. Rules area added, and if too many rules are added, the LoadBalancer deployment fails with:

Warning  CreatingLoadBalancerFailed  17m service-controller  Error creating load balancer (will retry): failed to ensure load balancer for service xx/xxxxx: error authorizing security group ingress: "RulesPerSecurityGroupLimitExceeded: The maximum number of rules per security group has been reached.\n\tstatus code: 400, request id: a4fc17a6-8803-4fb4-ac78-ee0db99030e0"

The solution was to locate a node → Security → Security groups → pick the SG with "kubernetes.io/rule/nlb/" rules, and delete inbound "kubernetes.io/rule/nlb/" rules.

Storage

Amazon EFS CSI

Amazon EFS CSI

eksctl

eksctl