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Provisioning a Kubernetes Cluster on AWS using Ansible

Setup

  • AWS VPC
  • 3 EC2 instances for HA Kubernetes Control Plane: Kubernetes API, Scheduler and Controller Manager
  • 3 EC2 instances for etcd cluster
  • 3 EC2 instances as Kubernetes Workers (aka Minions or Nodes)
  • Kubenet Pod networking (using CNI)
  • HTTPS between components and control API
  • Sample nginx service deployed to check everything works

Requirements

Requirements on control machine:

  • Python (tested with Python 2.7.12, may be not compatible with older versions; requires Jinja2 2.8)
  • Python netaddr module
  • Ansible (tested with Ansible 2.1.0.0)
  • cfssl and cfssljson: https://github.com/cloudflare/cfssl
  • Kubernetes CLI
  • SSH Agent

AWS Credentials

AWS KeyPair

You need a valid AWS Identity (.pem) file and the corresponding Public Key. Terraform imports the KeyPair in your AWS account. Ansible uses the Identity to SSH into machines.

Ansible authentication

Ansible expect AWS credentials set in environment variables:

$ export AWS_ACCESS_KEY_ID=<access-key-id>
$ export AWS_SECRET_ACCESS_KEY="<secret-key>"

Ansible expects the SSH identity loaded by SSH agent:

$ ssh-add <keypair-name>.pem

Defining the environment

  • control_cidr: The CIDR of your IP. All instances will accept only traffic from this address only. Note this is a CIDR, not a single IP. e.g. 123.45.67.89/32 (mandatory)
  • default_keypair_public_key: Valid public key corresponding to the Identity you will use to SSH into VMs. e.g. "ssh-rsa AAA....xyz" (mandatory)

Note that Instances and Kubernetes API will be accessible only from the "control IP". If you fail to set it correctly, you will not be able to SSH into machines or run Ansible playbooks.

You may optionally redefine:

  • default_keypair_name: AWS key-pair name for all instances. (Default: "k8s-not-the-hardest-way")
  • vpc_name: VPC Name. Must be unique in the AWS Account (Default: "kubernetes")
  • elb_name: ELB Name for Kubernetes API. Can only contain characters valid for DNS names. Must be unique in the AWS Account (Default: "kubernetes")
  • owner: Owner tag added to all AWS resources. No functional use. It becomes useful to filter your resources on AWS console if you are sharing the same AWS account with others. (Default: "kubernetes")

Install Kubernetes with Ansible

Run Ansible commands from ./ansible subdirectory.

Install Kubernetes components and etcd cluster.

$ ansible-playbook infra.yaml

Setup Kubernetes CLI

Configure Kubernetes CLI (kubectl) on your machine, setting Kubernetes API endpoint.

$ ansible-playbook kubectl.yaml --extra-vars "kubernetes_api_endpoint=<kubernetes-api-dns-name>"

Verify all components and minions (workers) are up and running, using Kubernetes CLI (kubectl).

$ kubectl get componentstatuses
NAME                 STATUS    MESSAGE              ERROR
controller-manager   Healthy   ok
scheduler            Healthy   ok
etcd-2               Healthy   {"health": "true"}
etcd-1               Healthy   {"health": "true"}
etcd-0               Healthy   {"health": "true"}

$ kubectl get nodes
NAME                                       STATUS    AGE
ip-10-43-0-30.eu-west-1.compute.internal   Ready     6m
ip-10-43-0-31.eu-west-1.compute.internal   Ready     6m
ip-10-43-0-32.eu-west-1.compute.internal   Ready     6m

Setup Pod cluster routing

Set up additional routes for traffic between Pods.

$ ansible-playbook kubernetes-routing.yaml

Deploy a ngnix service inside Kubernetes.

$ ansible-playbook kubernetes-nginx.yaml

Verify pods and service are up and running.

$ kubectl get pods -o wide
NAME                     READY     STATUS    RESTARTS   AGE       IP           NODE
nginx-2032906785-9chju   1/1       Running   0          3m        10.200.1.2   ip-10-43-0-31.eu-west-1.compute.internal
nginx-2032906785-anu2z   1/1       Running   0          3m        10.200.2.3   ip-10-43-0-30.eu-west-1.compute.internal
nginx-2032906785-ynuhi   1/1       Running   0          3m        10.200.0.3   ip-10-43-0-32.eu-west-1.compute.internal

> kubectl get svc nginx --output=json
{
    "kind": "Service",
    "apiVersion": "v1",
    "metadata": {
        "name": "nginx",
        "namespace": "default",
...

Retrieve the port nginx has been exposed on:

$ kubectl get svc nginx --output=jsonpath='{range .spec.ports[0]}{.nodePort}'
32700

Now you should be able to access nginx default page:

$ curl http://<worker-0-public-ip>:<exposed-port>
<!DOCTYPE html>
<html>
<head>
<title>Welcome to nginx!</title>
...