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Practical guide to Kubernetes Multi node control plane

Requirements

Before using terraform script you have to prepare default aws profile and adjust aws region in variables.tf

Install infrastructure with Terraform

What it does

  • Create ASG for control plane nodes
  • Create ASG for worker nodes
  • Create NLB Load balancer for control plane

How AWS resources are related to each other

  • aws_launch_template(LT) - define instance parameters
  • aws_autoscaling_group(ASG) - use LT and define VPC subnets
  • aws_autoscaling_attachment - connect TG with ASG
  • aws_lb_target_group(TG) - define vpc
  • aws_lb(LB) - define subnets
  • aws_lb_listener - connect LB with TG

Apply Terrafom

terraform init
terraform plan
terraform apply

Activate control plane Kubernetes nodes

For easy steup and testing all EC2 nodes have public ip.

Create first control plane node

Run on first master node. You can choose any ec2 server as first master from master group.

kubeadm init --control-plane-endpoint "LOAD_BALANCER_DNS:LOAD_BALANCER_PORT" --upload-certs --pod-network-cidr=192.168.0.0/16

To access our api server from laptop require public load balancer which will forward TCP connection to control plane instances.

Internet facing NLB require instances security group to open inbound connection from client ips, so if our client is laptop it mean to open connection to VPN public ip.

To start using your cluster, you need to run the following as a regular user:

mkdir -p $HOME/.kube
sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
sudo chown $(id -u):$(id -g) $HOME/.kube/config

Install network plugin

Note: Some CNI network plugins like Calico require a CIDR such as 192.168.0.0/16 and some like Weave do not. See the CNI network documentation.

WeaveWorks plugin: kubectl apply -f "https://cloud.weave.works/k8s/net?k8s-version=$(kubectl version | base64 | tr -d '\n')"

Calico plugin: kubectl apply -f https://docs.projectcalico.org/v3.11/manifests/calico.yaml

Note: Possible issue with CNI plugin on AWS - Available ENIs left dangling after node termination #608

Join additional control plan nodes

Run on other master nodes.

kubeadm join 192.168.0.200:6443 --token 9vr73a.a8uxyaju799qwdjv --discovery-token-ca-cert-hash sha256:7c2e69131a36ae2a042a339b33381c6d0d43887e2de83720eff5359e26aec866 --control-plane --certificate-key f8902e114ef118304e561c3ecd4d0b543adc226b7a07f675f56564185ffe0c07

Note: Please note that the certificate-key gives access to cluster sensitive data, keep it secret! As a safeguard, uploaded-certs will be deleted in two hours; If necessary, you can use kubeadm init phase upload-certs to reload certs afterward

To re-upload the certificates and generate a new decryption key, use the following command on a control plane node that is already joined to the cluster:

sudo kubeadm init phase upload-certs --upload-certs

Join worker nodes

Run on each worker. kubeadm join 192.168.0.200:6443 --token 9vr73a.a8uxyaju799qwdjv --discovery-token-ca-cert-hash sha256:7c2e69131a36ae2a042a339b33381c6d0d43887e2de83720eff5359e26aec866