Docker Compose - NodeJS with MongoDB

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Git Repo

Clone this repo: node-mongodb-docker-compose, then, we'll see the follwong files:

.
├── Dockerfile
├── README.md
├── docker-compose.yml
├── index.js
├── models
│.. └── Item.js
├── package-lock.json
├── package.json
└── views
    └── index.ejs

In this post, we'll create Node and MongoDB containers. Even though the Node app is very simple, we'll learn how to use docker-compose.

Docker compose

Basically, the Compose file maps the docker run command(s) into a file and it is so convenient as we do not have to type all the parameters to pass to the docker run command. We can declaratively do that in the Compose file.

Note that unlike the docker run command, with Docker compose we don't have to define any network. That's because the Docker compose takes care of creating a common network between containers. It creates a network named as "working-directory__default". In our case, it's node-mongodb-docker-compose_default. We can see it from the message when we run docker-compose.

docker-compose.yml:

version: '3'
services:
  node:
    restart: always
    build: .
    ports:
      - 80:3000
    volumes:
      - ./:/code
  mongo:
    image: mongo
    ports:
      - 27017:27017
    volumes:
      - mongodb:/data/db
volumes:
 mongodb:

Dockerfile:

FROM node:12.18.1
WORKDIR /app
COPY ["package.json", "package-lock.json*", "./"]
RUN npm install
COPY . .
CMD ["npm", "start"]

In the Dockerfile, we are creating a working directory, WORKDIR /app to instruct Docker to use this path as the default location for all subsequent commands. This way we do not have to type out full file paths but can use relative paths based on the working directory.
Before we run npm install, we need to get our package.json and package-lock.json files into our images using COPY command. We copy the package.json and package-lock.json files into our working directory /app.
Once we have our package.json files inside the image, we can use the RUN command to execute the command npm install. This works exactly the same as if we were running npm install locally on our machine, but this time these Node modules will be installed into the node_modules directory inside our image.
After RUN npm install, we have an image that is based on node version 12.18.1 and we have installed our dependencies.
COPY . . adds our source code into the image. It takes all the files located in the current directory and copies them into the image.
Now, we want to tell Docker what command we want to run when our image is run inside of a container via CMD [ "npm", "start" ].

To start the container run this command:

$ docker-compose up -d --build
Creating network "node-mongodb-docker-compose_default" with the default driver
Creating volume "node-mongodb-docker-compose_mongodb" with default driver
Building node
Step 1/6 : FROM node:12.18.1
 ---> f5be1883c8e0
Step 2/6 : WORKDIR /app
 ---> Using cache
 ---> 85bc58f66633
Step 3/6 : COPY ["package.json", "package-lock.json*", "./"]
 ---> Using cache
 ---> cd7d5b7a31ae
Step 4/6 : RUN npm install
 ---> Using cache
 ---> 7f2a7b56d1b7
Step 5/6 : COPY . .
 ---> Using cache
 ---> 34198675b1fa
Step 6/6 : CMD ["npm", "start"]
 ---> Using cache
 ---> 728c01a1eb0c
Successfully built 728c01a1eb0c
Successfully tagged node-mongodb-docker-compose_node:latest
Creating node-mongodb-docker-compose_mongo_1 ... done
Creating node-mongodb-docker-compose_node_1  ... done

$ docker ps
CONTAINER ID        IMAGE                              COMMAND                  CREATED             STATUS              PORTS                      NAMES
166efd4e492b        mongo                              "docker-entrypoint.s…"   30 seconds ago      Up 29 seconds       0.0.0.0:27017->27017/tcp   node-mongodb-docker-compose_mongo_1
34073f1926e1        node-mongodb-docker-compose_node   "docker-entrypoint.s…"   30 seconds ago      Up 29 seconds       0.0.0.0:80->3000/tcp       node-mongodb-docker-compose_node_1

Note that we need to use --build if any changes have been made to our Node code (such as views/index.ejs or index.js) since it tells the compose to rebuild the image for our node container.

Here is our app after two inputs:

Note that the data persists since we're using Docker volume (named volume) which is the preferred mechanism for persisting data generated by and used by Docker containers:

$ docker volume ls
local               node-mongodb-docker-compose_mongodb

So, the data persists and we can continue to add items even after we re-run the containers:

$ docker-compose down
$ docker-compose up -d

To tear down our containers, we need to use docker-compose down:

$ docker-compose down
Stopping node-mongodb-docker-compose_mongo_1 ... done
Stopping node-mongodb-docker-compose_node_1  ... done
Removing node-mongodb-docker-compose_mongo_1 ... done
Removing node-mongodb-docker-compose_node_1  ... done
Removing network node-mongodb-docker-compose_default

As we can see it removes not only the containers but also the network created by the docker-compise up command.