12. HANDS-ON TUTORIAL: Scaling Containers over Multiple Instances using Docker Swarm

12. HANDS-ON TUTORIAL: Scaling Containers over Multiple Instances using Docker Swarm

Increasing scalability, availability, & reliability


This introduction provides an overview of the steps required to deploy microservices in containers across three instances using Docker Swarm. The process begins with installing Docker and Docker Compose on all instances, followed by initializing a Swarm manager and joining workers to the manager. The microservices are then deployed on the Swarm using a compose file, and the public IP of the manager is used to access the services in a web browser. The final step is to check the status of the services to ensure they have started successfully.

Tools Utilised

  • Ubuntu

  • Docker

  • Docker-Compose

  • Docker Swarm

  • Git

  • GitHub

  • Python

  • Flask

  • MySQL


Step-by-Step Guide

Install Docker & Docker Compose on ALL INSTANCES

Docker Swarm already comes installed with Docker.

1. Update and install the necessary packages

sudo apt update && sudo apt install curl jq -y

2. Use the official Docker script to install Docker

To install Docker on Linux, we can use an official script from get.docker.com:

curl https://get.docker.com | sudo bash

3. Add the current user to the docker group

The script installs Docker and creates a Docker user group with access to the commands. This means that Docker can only be used with sudo privileges or if the current user is in the Docker user group:

sudo usermod -aG docker $(whoami)

4. Give /var/run/docker.sock correct permissions

sudo chmod 666 /var/run/docker.sock

5. Test Docker works

docker run --rm hello-world

The --rm flag removes the container when it exits or when the daemon exits.

6. Set the version of Docker-Compose to download

version=$(curl -s https://api.github.com/repos/docker/compose/releases/latest | jq -r '.tag_name')

7. Download Docker-Compose to /usr/local/bin/

sudo curl -L "https://github.com/docker/compose/releases/download/${version}/docker-compose-$(uname -s)-$(uname -m)" -o /usr/local/bin/docker-compose

8. Make the file executable

sudo chmod +x /usr/local/bin/docker-compose

9. Verify the installation by checking the version

docker-compose --version

Docker Swarm Setup

10. Initialise the Swarm on manager-node

sudo docker swarm init

11. Copy the command provided in the terminal


12. Enter the join command on worker-node-1 & worker-node-2


sudo docker swarm join --token SWMTKN-1-3ax04jx5w6svrrvjrjyryt5hubvlxra7am1lb2gqysgtpgulwd-4xfpw2vcpoeefrztu4kagdv6f



Deploy Microservices in Docker Swarm

13. On manager-node, clone the repo and go into the folder

git clone https://github.com/mrbilalshafiq/DevOps-Project-2 && cd DevOps-Project-2/

14. Still on the manager-node, start the containers using Docker Swarm and the docker-compose.yaml file

sudo docker stack deploy --compose-file docker-compose.yaml Project2

15. View Containers on all nodes

docker ps

16. Find your public IP on all nodes

curl ifconfig.me

17. Access the application using all 3 IP addresses



In conclusion, Docker Swarm is a powerful tool that can greatly benefit companies by enabling them to easily deploy and manage microservices in a containerized environment. With its ability to scale and distribute services across multiple instances, Docker Swarm ensures high availability and fault tolerance, making it a reliable solution for companies that rely on microservices to power their applications.

Additionally, the use of Docker and Docker Compose simplifies the process of building, shipping and running containers, making it a valuable addition to any company's DevOps toolkit. By following the step-by-step guide provided in this blog post, you can successfully implement Docker Swarm and take advantage of its benefits to improve the performance and reliability of their microservices.

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