Load Balancing Containers

1.5 hours
  • 4 Learning Objectives

About this Hands-on Lab

For the last six months, the Acme Anvil Corporation has been migrating some of their bare metal infrastructure to Docker containers. The initial implementation was very basic and lacked any kind of load balancing. Your manager has tasked you with creating two proofs of concept. For the first proof of concept, you are to use Docker Compose to create an Nginx load balancer and three instances using your `weather-app` image. Nginx will use port 80 and send traffic to port 3000 on the `weather-app` containers. For the second proof of concept, you are to create a Docker Swarm service called `nginx-app` that has two replicas using the Nginx image. The service should be published to port 8080 on the host and target port 80 on the containers.

Learning Objectives

Successfully complete this lab by achieving the following learning objectives:

Create a Docker Compose file.

The containers of your docker-compose.yml should look like the following:

version: '3.2'
services:
  weather-app1:
      build: ./weather-app
      tty: true
      networks:
       - frontend
  weather-app2:
      build: ./weather-app
      tty: true
      networks:
       - frontend
  weather-app3:
      build: ./weather-app
      tty: true
      networks:
       - frontend

  loadbalancer:
      build: ./load-balancer
      image: nginx
      tty: true
      ports:
       - '80:80'
      networks:
       - frontend

networks:
  frontend:
Update `nginx.conf`.

The contents of your nginx.conf file should look like the following:

events { worker_connections 1024; }

http {
  upstream localhost {
    server weather-app1:3000;
    server weather-app2:3000;
    server weather-app3:3000;
  }
  server {
    listen 80;
    server_name localhost;
    location / {
      proxy_pass http://localhost;
      proxy_set_header Host $host;
    }
  }
}
Execute `docker-compose up`.

Execute a docker-compose up:

/usr/local/bin/docker-compose up --build -d
Create a Docker service using Docker Swarm.

Create a Docker service by executing the following command:

docker service create --name nginx-app --publish published=8080,target=80 --replicas=2 nginx

Additional Resources

In this lab, you will load balance containers using two methods. First, you will use Nginx to load balance traffic to three weather-app containers. Next, you will use Docker Swarm to load-balance a pair of Nginx containers.

Log in to Swarm Server 1 and Swarm Server 2 and sudo su - to root.

Part 1

We will be using Docker Compose to set up the load balancer and containers.

  1. On Swarm Server 1, in the root directory, navigate to lb-challenge and create the Docker Compose file.
    • Set the Compose version to 3.2.
    • Create three weather-app services:
    • weather-app1
    • weather-app2
    • weather-app3
    • The services should build the Dockerfile that is in the weather-app directory.
    • All three should have tty set to true.
    • All three containers should be using the frontend network.
    • Create a service called loadbalancer.
    • It should use the Dockerfile located in the load-balancer directory.
    • Set tty to true.
    • The port mapping should be set to 80 on the host and 80 on the container.
    • The load balancer should be using the frontend network.

Create the Frontend Network

  1. In the load-balancer directory, there will be a file called nginx.conf.
    • Add the three weather-app services to the upstream section.
    • In the server section, make sure it is listening on port 80.
    • Set the server_name to localhost.
    • The location should be set to /.
    • The location should contain a proxy pass to localhost.
    • The proxy set header should be set to $host.
    • Execute a compose up and make sure to use the build and detached flags.
    • Verify that your app is up and running.

Part 2

  1. In the root directory, use cat to retrieve the contents of swarm-token.txt.
    • Use the docker swarm join --token command from the output of the file to join Swarm Server 2 to the swarm.
    • Create a service called nginx-app.
    • The published port should be 8080 and the target port should be 80 on the container.
    • Make sure there are 2 replicas.
    • Use the nginx image.
    • Verify that your app is up and running.
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