Nginx Load Balancing Tutorial

This tutorial will guide you through the process of setting up Nginx as a load balancer to distribute incoming traffic among three Docker containers running your application. The Nginx container and the application containers will be connected to the same Docker network and referenced using their respective names.

Prerequisites

Before starting this tutorial, ensure that you have the following:

• Docker installed on your system
• Basic understanding of Docker and Docker networks
• Familiarity with Nginx and its configuration

Step 1: Create a Docker Network

To establish communication between the Nginx container and the application containers, create a Docker network. Run the following command:

docker network create my-network

This will create a Docker network named my-network.

Step 2: Build and Run the Application Containers

1. In the express-app directory of your application, build the Docker image by running the following command:

   docker build -t my-app .

   This command builds the Docker image using the Dockerfile and tags it as my-app.

2. Start three containers for your application using the following commands:

   docker run --name app1 --network my-network -p 8080:8080 -d my-app
   docker run --name app2 --network my-network -p 8080:8080 -d my-app
   docker run --name app3 --network my-network -p 8080:8080 -d my-app

   These commands start three containers named app1, app2, and app3 respectively, exposing ports 8080, 8080, and 8080 on the host and connecting them to the my-network Docker network. Each container runs your application.

By following these steps, you build and run three instances of your application in separate Docker containers. Nginx, acting as the load balancer, will distribute incoming traffic among these containers.

Step 3: Configure Nginx

Use the file default.conf with the following configuration:

http {
    upstream loadbalance {
        server app1:8080;
        server app2:8080;
        server app3:8080;
    }

    server {
        listen 80;
        location / {
            proxy_pass http://loadbalance;
        }
    }
}

In this configuration, the upstream block defines the three application containers using their names and the port they are running on. The server block listens on port 80 and forwards incoming requests to the loadbalance upstream.

Step 4: Build and Run the Nginx Container

FROM nginx:latest
COPY default.conf /etc/nginx/conf.d/default.conf

Build the Docker image by running the following command in the same directory as the Dockerfile:

docker build -t my-nginx .

Once the image is built, run the Nginx container with the following command:

docker run --name my-nginx --network my-network -p 80:80 -d my-nginx

This command starts a container named my-nginx, connects it to the my-network Docker network, maps port 80 of the host to port 80 of the container, and runs it in detached mode.

Step 5: Verify the Load Balancing

With the Nginx container and application containers running, you can test the load balancing. Open a web browser to send requests to http://localhost. Each request should be forwarded to one of the application containers in a round-robin fashion.

Congratulations! You have successfully set up Nginx as a load balancer between three Docker containers running your application.

Conclusion

This tutorial provided a step-by-step guide to configuring Nginx as a load balancer in a Docker environment. By following these instructions, you can distribute incoming traffic among multiple application containers.