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Create a network

In order for the containers to find each other, you will need to create a Docker network. Understanding how networking work in the containers land is out of the scope of this specific workshop. However, let's see how we can get our backend to connect to the MongoDB container.

Stop existing containers​

Make sure that you stop existing containers with the docker stop command.

docker stop mongodb
docker stop mern-k8s-back

Create a Docker Network​

Creating a Docker network requires a single command.

docker network create mern-k8s

You will now be able to restart your containers, and use this newly created network with the --network flag.

Restart the database container​

Restart your database container, but with the network flag this time. Now, this container will be reachable by the name provided with the --name flag. 

docker run --name mongodb --rm -d -p 27017:27017 -e MONGO_INITDB_ROOT_USERNAME=user -e MONGO_INITDB_ROOT_PASSWORD=pass --network mern-k8s mongo

Restart the backend​

Restart the backend container. This time, specify the --network flag, and change the connection string to use the mongodb container rather than 127.0.0.1.

docker run -d --rm --name mern-k8s-back -p 5000:5000 -e PORT=5000 -e CONN_STR="mongodb://user:pass@mongodb:27017" --network mern-k8s $DOCKER_HUB_USERNAME/mern-k8s-back

Test out the backend​

Try reaching your backend again.

curl localhost:5000/healthz

This time, you should see that the server is up and running, and that the database is connected.