How to get Docker containers to talk to each other while running on my local host?

Question

I have a Webapp running completely locally on my MacBook.

The Webapp has a Front End (Angular/Javascript) and a Back End (Python/Django) which implements a RESTful API.

I have Dockerized the Back End so that it is completely self-contained in a Docker Container and exposes port 8000. I map this port locally to 4026.

Now I need to Dockerize the Front End. But if I have these two docker containers running on my localhost, how can I get the FE to send HTTP requests to the BE? The FE container won't know anything that exists outside of it. Right?

This is how I run the FE:

$ http-server Starting up http-server, serving ./ Available on:   http://127.0.0.1:8080   http://192.168.1.16:8080 Hit CTRL-C to stop the server 

Please provide references explaining how I can achieve this.

Answer 1

The way to do this today is Docker Networking.

The short version is that you can run docker network ls to get a listing of your networks. By default, you should have one called bridge. You can either create a new one or use this one by passing --net=bridge when creating your container. From there, containers launched with the same network can communicate with each other over exposed ports.

If you use Docker Compose as has been mentioned, it will create a bridge network for you when you run docker-compose up with a name matching the folder of your project and _default appended. Each image defined in the Compose file will get launched in this network automatically.

With all that said, I'm guessing your frontend is a webserver that just serves up the HTML/JS/CSS and those pages access the backend service. If that's accurate, you don't really need container-to-container communication in this case anyway... both need to be exposed to the host since connections originate from the client system.

Answer 2

There are multiple ways to do this and the simplest answer is to use Docker-Compose. You can use Docker-compose to allow multiple services to run a server.

If you are not using Docker-Compose and running individual containers, then expose both services port with host and use those services on such on links like:

docker run -p 3306:3306 mysql docker run -p 8088:80 nginx  

Now you can communicate as:

http://hostip:3306  http://hostip:8088  

Now you can communicate with containers using hostIP.