dneary / nginxlb

A Docker-compose recipe to prove the concept of nginx load balancing.

Testing nginx load balancing with docker-compose

This project is a very basic configuration to run one nginx instance as a proxy, load balancing across 3 other nginx instances serving a static HTML file.

1. proxy: We map port 80 of localhost to port 80 of the nginx container. This container has a minimal configuration, defining an upstream host group called web consisting of three nodes web[123] and proxying all traffic to them.
2. web[123]: Trivially configured nginx nodes serving different static files to allow differentiation between the nodes.

Each of these containers is added to a bridge network for the application. These containers can reach each other by name (web[123] and proxy), but from the host, we cannot connect to them, except via the docker command.

Prerequisites

Throughout, we assume that you are running on a modern Linux distribution. The author uses the RHEL family of operating systems - CentOS Streams, AlmaLinux, Rocky Linux, Oracle Linux, but any platform-specific commands will be flagged. If you are using a Debian-family distribution, you will need to use an equivalent on those platforms.

We also assume that you have installed Docker (docker.io) and docker-compose. The instructions should work with podman and podman-compose, but we have not tested them.

We will also use git to check out the code from github.

We will want to run docker-compose as an unprivileged user, so we have to add our user to the docker group.

usermod -aG docker $USER

After running this, you need to ensure that you relaunch a login shell for the change to take effect. You can do this explicitly with:

sudo -s -u $USER

but for the change to take effect permanently in your instance, you will need to restart the sshd service. On the RHEL family, this means:

sudo systemctl restart sshd

The next time you connect to your instance with ssh, you should see docker group in the output of groups for your user.

To test that you now have Docker correctly installed and configured, run:

docker run hello-world

You should see a Docker container being downloaded from dockerhub, and a message confirming that your installation appears to be running correctly.

Getting started

Now that we have things set up, check out this project:

git clone https://github.com/dneary/nginxlb.git
cd nginxlb

We should now be ready to run:

docker-compose up -d

This will process the docker-compose.yml file in this directory, download the nginx container, and start four copies of it, one node called proxy with the config in nginx/proxyconf.d, and three with the identical trivial config in nginx/conf.d. After running docker-compose, if all goes well, you should now be able to go to http://localhost:80 and see which servers you are connecting to.