How to network 2 separate docker containers to communicate with eachother?

Question

I'm pretty new to docker, and I've tried searching about networking but haven't found a solution that's worked.

I have a Laravel app that is using Laradock. I also have an external 3rd party API that runs in its own docker container. I basically want to specify the container name of the api inside my laravel.env file, and have it dynamically resolve the container ip so I can make API calls from my Laravel app. I can already do this with services that are already part of laradock like mariadb/mysql, but since my API is located in an external container, it can't connect to it.

I tried making a network and attaching them with;

docker network create my-network

Then inside my docker-compose.yml files for each of the containers, I specified;

networks:
  my-network:
    name: "my-network"

But if I try and ping them with;

docker exec -ti laradock-workspace-1 ping my-api

I can't connect and can't really figure out why. Was hoping someone familiar with docker might be able to explain why since I'm sure it's something very obvious I'm missing. Thanks!

Answer 1

By default Docker Compose uses a bridge network to provision inter-container communication. Read this article for more info about inter-container networking.

What matters for you, is that by default Docker Compose creates a hostname that equals the service name in the docker-compose.yml file. Consider the following docker-compose.yml :

version: '3.9'
services:
  server:
    image: node:16.9.0
    container_name: server
    tty: true
    stdin_open: true
    depends_on:
       - mongo
    command: bash

  mongo:
    image: mongo
    environment:
      MONGO_INITDB_DATABASE: my-database

When you run docker-compose up , Docker will create a default network and assigns the service name as hostname for both mongo and server .

You can now access the backend container via:

docker exec -it server bash

And now you can ping the mongo container using Dockers internal network (default on port 27017 in this case):

curl -v http://mongo:27017/my-database

That's it. The same applies for your setup.