Author: Naresh L J (Infosys)
Objective
This blog post describes the steps required to setup a multi node Kubernetes cluster for development purposes. This setup provides a production-like cluster that can be setup on your local machine.
Why do we require multi node cluster setup?
Multi node Kubernetes clusters offer a production-like environment which has various advantages. Even though Minikube provides an excellent platform for getting started, it doesn’t provide the opportunity to work with multi node clusters which can help solve problems or bugs that are related to application design and architecture. For instance, Ops can reproduce an issue in a multi node cluster environment, Testers can deploy multiple versions of an application for executing test cases and verifying changes. These benefits enable teams to resolve issues faster which make the more agile.
Why use Vagrant and Ansible?
Vagrant is a tool that will allow us to create a virtual environment easily and it eliminates pitfalls that cause the works-on-my-machine phenomenon. It can be used with multiple providers such as Oracle VirtualBox, VMware, Docker, and so on. It allows us to create a disposable environment by making use of configuration files.
Ansible is an infrastructure automation engine that automates software configuration management. It is agentless and allows us to use SSH keys for connecting to remote machines. Ansible playbooks are written in yaml and offer inventory management in simple text files.
Prerequisites
- Vagrant should be installed on your machine. Installation binaries can be found here.
- Oracle VirtualBox can be used as a Vagrant provider or make use of similar providers as described in Vagrant’s official documentation.
- Ansible should be installed in your machine. Refer to the Ansible installation guide for platform specific installation.
Setup overview
We will be setting up a Kubernetes cluster that will consist of one master and two worker nodes. All the nodes will run Ubuntu Xenial 64-bit OS and Ansible playbooks will be used for provisioning.
Step 1: Creating a Vagrantfile
Use the text editor of your choice and create a file with named Vagrantfile, inserting the code below. The value of N denotes the number of nodes present in the cluster, it can be modified accordingly. In the below example, we are setting the value of N as 2.
IMAGE_NAME = "bento/ubuntu-16.04"
N = 2
Vagrant.configure("2") do |config|
config.ssh.insert_key = false
config.vm.provider "virtualbox" do |v|
v.memory = 1024
v.cpus = 2
end
config.vm.define "k8s-master" do |master|
master.vm.box = IMAGE_NAME
master.vm.network "private_network", ip: "192.168.50.10"
master.vm.hostname = "k8s-master"
master.vm.provision "ansible" do |ansible|
ansible.playbook = "kubernetes-setup/master-playbook.yml"
end
end
(1..N).each do |i|
config.vm.define "node-#{i}" do |node|
node.vm.box = IMAGE_NAME
node.vm.network "private_network", ip: "192.168.50.#{i + 10}"
node.vm.hostname = "node-#{i}"
node.vm.provision "ansible" do |ansible|
ansible.playbook = "kubernetes-setup/node-playbook.yml"
end
end
end
Step 2: Create an Ansible playbook for Kubernetes master.
Create a directory named kubernetes-setup in the same directory as the Vagrantfile. Create two files named master-playbook.yml and node-playbook.yml in the directory kubernetes-setup.
In the file master-playbook.yml, add the code below.
Step 2.1: Install Docker and its dependent components.
We will be installing the following packages, and then adding a user named “vagrant” to the “docker” group.
– docker-ce
– docker-ce-cli
– containerd.io
---
- hosts: all
become: true
tasks:
- name: Install packages that allow apt to be used over HTTPS
apt:
name: "{{ packages }}"
state: present
update_cache: yes
vars:
packages:
- apt-transport-https
- ca-certificates
- curl
- gnupg-agent
- software-properties-common
- name: Add an apt signing key for Docker
apt_key:
url: https://download.docker.com/linux/ubuntu/gpg
state: present
- name: Add apt repository for stable version
apt_repository:
repo: deb [arch=amd64] https://download.docker.com/linux/ubuntu xenial stable
state: present
- name: Install docker and its dependecies
apt:
name: "{{ packages }}"
state: present
update_cache: yes
vars:
packages:
- docker-ce
- docker-ce-cli
- containerd.io
notify:
- docker status
- name: Add vagrant user to docker group
user:
name: vagrant
group: docker
Step 2.2: Kubelet will not start if the system has swap enabled, so we are disabling swap using the below code.
- name: Remove swapfile from /etc/fstab
mount:
name: "{{ item }}"
fstype: swap
state: absent
with_items:
- swap
- none
- name: Disable swap
command: swapoff -a
when: ansible_swaptotal_mb > 0
Step 2.3: Installing kubelet, kubeadm and kubectl using the below code.
- name: Add an apt signing key for Kubernetes
apt_key:
url: https://packages.cloud.google.com/apt/doc/apt-key.gpg
state: present
- name: Adding apt repository for Kubernetes
apt_repository:
repo: deb https://apt.kubernetes.io/ kubernetes-xenial main
state: present
filename: kubernetes.list
- name: Install Kubernetes binaries
apt:
name: "{{ packages }}"
state: present
update_cache: yes
vars:
packages:
- kubelet
- kubeadm
- kubectl
Step 2.3: Initialize the Kubernetes cluster with kubeadm using the below code (applicable only on master node).
- name: Initialize the Kubernetes cluster using kubeadm
command: kubeadm init --apiserver-advertise-address="192.168.50.10" --apiserver-cert-extra-sans="192.168.50.10" --node-name k8s-master --pod-network-cidr=192.168.0.0/16
Step 2.4: Setup the kube config file for the vagrant user to access the Kubernetes cluster using the below code.
- name: Setup kubeconfig for vagrant user
command: "{{ item }}"
with_items:
- mkdir -p /home/vagrant/.kube
- cp -i /etc/kubernetes/admin.conf /home/vagrant/.kube/config
- chown vagrant:vagrant /home/vagrant/.kube/config
Step 2.5: Setup the container networking provider and the network policy engine using the below code.
- name: Install calico pod network
become: false
command: kubectl create -f https://docs.projectcalico.org/v3.4/getting-started/kubernetes/installation/hosted/calico.yaml
Step 2.6: Generate kube join command for joining the node to the Kubernetes cluster and store the command in the file named join-command.
- name: Generate join command
command: kubeadm token create --print-join-command
register: join_command
- name: Copy join command to local file
local_action: copy content="{{ join_command.stdout_lines[0] }}" dest="./join-command"
Step 2.7: Setup a handler for checking Docker daemon using the below code.
handlers:
- name: docker status
service: name=docker state=started
Step 3: Create the Ansible playbook for Kubernetes node.
Create a file named node-playbook.yml in the directory kubernetes-setup.
Add the code below into node-playbook.yml
Step 3.1: Start adding the code from Steps 2.1 till 2.3.
Step 3.2: Join the nodes to the Kubernetes cluster using below code.
- name: Copy the join command to server location
copy: src=join-command dest=/tmp/join-command.sh mode=0777
- name: Join the node to cluster
command: sh /tmp/join-command.sh
Step 3.3: Add the code from step 2.7 to finish this playbook.
Step 4: Upon completing the Vagrantfile and playbooks follow the below steps.
$ cd /path/to/Vagrantfile
$ vagrant up
Upon completion of all the above steps, the Kubernetes cluster should be up and running.
We can login to the master or worker nodes using Vagrant as follows:
$ ## Accessing master
$ vagrant ssh k8s-master
vagrant@k8s-master:~$ kubectl get nodes
NAME STATUS ROLES AGE VERSION
k8s-master Ready master 18m v1.13.3
node-1 Ready <none> 12m v1.13.3
node-2 Ready <none> 6m22s v1.13.3
$ ## Accessing nodes
$ vagrant ssh node-1
$ vagrant ssh node-2
