Posted on Sep 21, 2020

Build images and run them with docker compose

In the previous post, we saw how we can run more than one containers and how to route requests to them using nginx.

Of course, we had to build 3 images individually, and then run the three images in sequence to get the final ecosystem.

In this post, we'll try to combine all the steps in just one command using docker-compose.

We'll start with the same repo, where the previous post's code is checked in, clone it locally, and then setup the docker-compose yml file, and run it.

Step 1. Clone the codebase.

Clone the repo https://github.com/tirthaguha/container-reverse-proxy.

Step 2. Create the YML file

Network Drivers

Okay, so before we create the docker-compose.yml file, its important to understand how networking works in docker-compose.
Docker can create a virtual network for you to abstract the complexities of networking, and all your containers run and interact in that network. One interesting thing about this virtual network is the network driver. Based on your container ecosystem setup, the drivers can be bridge, overlay and macvlan.
In our case, since we're going to run all the containers in the same host, we're going to chose bridge network driver in our docker compose file. You may have a look into this article and learn more about docker networks

Create the docker compose file

docker-compose.yml is a file that contains all the information about the applications, their Dockerfiles and the network they are going to run in.

Here's our annotated docker-compose.yml that you need to put in your container-reverse-proxy directory.

version: "3" # start by defining the services services: # this is the first nodeJS application nodejs_1: # lets keep name of the image as first-app image: first-app # this is where the Dockerfile is compiled into an image build: # where is the Dockerfile kept, relative to this directory context: ./first-app # obviously, the Dockerfile in that directory dockerfile: Dockerfile # port mapping ports: - 3000:3000 # name of the container container_name: first-app # if the container crashes, it would be restarted automatically restart: unless-stopped # the virtual network of which this container will be a part of networks: - app-network # this is the second nodeJS application nodejs_2: # lets keep name of the image as first-app image: second-app build: # where is the Dockerfile kept, relative to this directory context: ./second-app dockerfile: Dockerfile ports: - 4000:4000 container_name: second-app restart: unless-stopped networks: - app-network # Finally, the nginx, that controlls the route nginx-server: image: nginx-load-balancer build: context: ./nginx dockerfile: Dockerfile ports: - 8080:80 container_name: nginx-load-balancer restart: unless-stopped networks: - app-network # the mysterious item, network networks: app-network: driver: bridge