<h1 style='font-size:26px;color:#6aa84f;'>docker: link a node.js container with a mongodb container in a isolated network</h1>

In our last tutorial we have seen, how a Legacy Linking of a mongodb and a webserver can be created

Now we want to create linked containers in an isolated network. That is good if you want to keep your containers strictly seperate from other container constructs. So you can be sure that everything in your dev enviroment is on its own area.

Prerequisits

We need some things installed on the local machine.

• docker installed
• git installed 
• a dockerhub account (visit http://hub.docker.com)

If you have our testapp and database image already installed, you can skip the next 2 sections and start with "Create your isolated network"

 

Install node.js pet-app

We want to use a little pet app with node.js. It starts an express server and connects to a mongodb server "my-mongodb". The app simply lists some docs pics and some describing texts

Clone the app repository in your projectroot

$ git clone https://github.com/pboethig/dockerlessons.git

$ cd dockerlessons/legacyLinking

 

Inspect the dockerfile

In the projectroot you find a "node.dockerfile" this is the dockerfile for our node webserver with the node.js app in it

This is the content

FROM node:latest

MAINTAINER Peter Böthig

ENV NODE_ENV=production
ENV PORT=3000

COPY . /var/www
WORKDIR /var/www

RUN npm install

EXPOSE $PORT

ENTRYPOINT ["npm", "start"]

To explain that

• Line 1 load a node baseimage
• Line 2 define a maintainer (your username in thinat case)
• Line 3 & 4 define enviromentvariables, to switch from dev to prod
• Line 5 copy our sourcecode to the container in "var/www"
• LINE 6 define a workingdirectory
• Line 7 run npm install
• Line 8 Expose the default webserverport (prod/live)
• Line 9 start the express webserver

In the follwing we use <your_docker_username>. Please make sure you have an account

 

Create our image from the Dockerfile

Now, that we have created our Dockerfile we can create our first image from it.

Open a terminal in the folder where your Dockerfile lives

docker build -f node.dockerfile -t <your_docker_username>/node-pet-app .

Don't forget the last point at the end of the line, otherwhis nothing will be found to image. The first load could take some seconds.

You can see you new image with

docker images

Create your mongo-database-container

Our pet app needs a mongodatabase where the pet data live. We simply use an image from the docker hiu

Pull the image and create a named container

docker run -d --name my-mongodb mongo

This will download the mongo-image and create a container "my-mongodb". The name "my-mongodb" is important, because it's  mapped to the configured databasename "mongodb" in our config/config.production.js of our pet app.

 

Create your isolated network

This task is pretty simple.

Create custom bridged network

docker network create --driver bridge first_isoltated_network 

Now you can check, if everything went fine:

docker network ls

This will list all networks. You should see your "first_isolated_network"

Inspect your network

docker network inspect first_isolated_network

This will show your networkconfiguration. At the moment the "containers" object is empty.

Create our mongodb container and link it to our isolated_network

Now that we have created our "first_isolated_network" lets add the mongodb container to it

Add mongodb to the network

docker run -d --net=first_isolated_network --name mongodb mongo

As you can see, there is a "--net=first_private_network" attribute, wich adds the created xontainer to our network

Inspect your network again

docker network inspect first_isolated_network 

This will now show you your mongo db container in the containers section.

Create our node-js container and link it to our isolated_network

Now we do the same with our node-js container. The one specific this is, that we directly link the app container to the database too.

Add node app to the network

docker run -d --net=first_isolated_network --name nodeapp

As you can see, there is a "--net=first_private_network" attribute, wich adds the created xontainer to our network

Inspect your network again

docker network inspect first_isolated_network 

This will now show you your "nodeapp" and your "mongodb" containers in the containers section of your network.

That's totaly creazy. I love that for the moment.

At last we want to populate some data again.

Populate data

docker exec nodeapp node dbSeeder.js

Now you can reach your app under http://localhost:8080