Using Docker Compose for NodeJS Development
Tags: docker, node, development
Published: 2017-06-13 11:24:32

---
title: Using Docker Compose for NodeJS Development
published: true
description: To provide an example of how you might move to containerized development, I built a simple todo API using NodeJS, Express, and PostgreSQL using Docker Compose for development, testing, and eventually in my CI/CD pipeline. 
tags: docker, node, development
cover_image: https://1npo9l3lml0zvr6w62acc3t1-wpengine.netdna-ssl.com/wp-content/uploads/2017/05/Heading_Using-Docker-Compose-for-NodeJS-Development.jpg
---

>This post was originally published on the [Codeship Blog](https://blog.codeship.com/using-docker-compose-for-nodejs-development/) and is posted here with the author's permission.

Docker is an amazing tool for developers. It allows us to build and replicate images on any host, removing the inconsistencies of dev environments and reducing onboarding timelines considerably.

To provide an example of how you might move to containerized development, I built a simple `todo` API using NodeJS, Express, and PostgreSQL using [Docker Compose](https://docs.docker.com/compose/) for development, testing, and eventually in my CI/CD pipeline.

In a two-part series, I will cover the development and pipeline creation steps. In this post, I will cover the first part: developing and testing with Docker Compose.

## Requirements for This Tutorial

This tutorial requires you to have a few items before you can get started.

*   Install [Docker Community Edition](https://store.docker.com/search?type=edition&offering=community)
*   Install [Docker Compose](https://docs.docker.com/compose/install/)
*   Download [Todo App Example - Non- Docker branch](https://github.com/codeship-library/nodejs-express-todoapp/archive/non-docker.zip)

The todo app here is essentially a stand-in, and you could replace it with your own application. Some of the setup here is specific for this application, and the needs of your application may not be covered, but it should be a good starting point for you to get the concepts needed to Dockerize your own applications.

Once you have everything set up, you can move on to the next section.

## Creating the Dockerfile

At the foundation of any Dockerized application, you will find a [`Dockerfile`](https://docs.docker.com/engine/reference/builder/). The `Dockerfile` contains all of the instructions used to build out the application image. You can set this up by installing NodeJS and all of its dependencies; however the Docker ecosystem has an image repository (the Docker Store) with a [NodeJS](https://store.docker.com/images/node?tab=description) image already created and ready to use.

In the root directory of the application, create a new `Dockerfile`.

```bash
/> touch Dockerfile
```

Open the newly created `Dockerfile` in your favorite editor. The first instruction, [`FROM`](https://docs.docker.com/engine/reference/builder/#from), will tell Docker to use the prebuilt NodeJS image. There are several choices, but this project uses the `node:7.7.2-alpine` image. For more details about why I'm using `alpine` here over the other options, you can read [this post](https://blog.codeship.com/alpine-based-docker-images-make-difference-real-world-apps/).

```bash
FROM node:7.7.2-alpine
```

If you run `docker build .`, you will see something similar to the following:

```bash
Sending build context to Docker daemon 249.3 kB
Step 1/1 : FROM node:7.7.2-alpine
7.7.2-alpine: Pulling from library/node
709515475419: Pull complete
1a7746e437f7: Pull complete
662ac7b95f9d: Pull complete
Digest: sha256:6dcd183eaf2852dd8c1079642c04cc2d1f777e4b34f2a534cc0ad328a98d7f73
Status: Downloaded newer image for node:7.7.2-alpine
 ---> 95b4a6de40c3
Successfully built 95b4a6de40c3

```

With only one instruction in the Dockerfile, this doesn't do too much, but it does show you the build process without too much happening. At this point, you now have an image created, and running `docker images` will show you the images you have available:

```bash
REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
node                7.7.2-alpine        95b4a6de40c3        6 weeks ago         59.2 MB
```

The `Dockerfile` needs more instructions to build out the application. Currently it’s only creating an image with NodeJS installed, but we still need our application code to run inside the container. Let's add some more instructions to do this and build this image again.

This particular Docker file uses [`RUN`](https://docs.docker.com/engine/reference/builder/#run), [`COPY`](https://docs.docker.com/engine/reference/builder/#copy), and [`WORKDIR`](https://docs.docker.com/engine/reference/builder/#workdir). You can read more about those on Docker's reference page to get a deeper understanding.

Let's add the instructions to the `Dockerfile` now:

```bash
FROM node:7.7.2-alpine

WORKDIR /usr/app

COPY package.json .
RUN npm install --quiet

COPY . .
```

Here is what is happening:

*   Set the working directory to `/usr/app`
*   Copy the `package.json` file to `/usr/app`
*   Install `node_modules`
*   Copy all the files from the project's root to `/usr/app`

You can now run `docker build .` again and see the results:

```bash
Sending build context to Docker daemon 249.3 kB
Step 1/5 : FROM node:7.7.2-alpine
  ---> 95b4a6de40c3
Step 2/5 : WORKDIR /usr/app
 ---> e215b737ca38
Removing intermediate container 3b0bb16a8721
Step 3/5 : COPY package.json .
 ---> 930082a35f18
Removing intermediate container ac3ab0693f61
Step 4/5 : RUN npm install --quiet
 ---> Running in 46a7dcbba114

 ### NPM MODULES INSTALLED ###

 ---> 525f662aeacf
 ---> dd46e9316b4d
Removing intermediate container 46a7dcbba114
Step 5/5 : COPY . .
 ---> 1493455bcf6b
Removing intermediate container 6d75df0498f9
Successfully built 1493455bcf6b
```

You have now successfully created the application image using Docker. Currently, however, our app won't do much since we still need a database, and we want to connect everything together. This is where Docker Compose will help us out.

## Docker Compose Services

Now that you know how to create an image with a `Dockerfile`, let's create an application as a service and connect it to a database. Then we can run some setup commands and be on our way to creating that new todo list.

Create the file `docker-compose.yml`:

```bash
/> touch docker-compose.yml
```

The [Docker Compose file](https://docs.docker.com/compose/compose-file/compose-file-v2/) will define and run the containers based on a configuration file. We are using [compose file version 2](https://docs.docker.com/compose/compose-file/compose-file-v2/) syntax, and you can read up on it on Docker's site.

An important concept to understand is that Docker Compose spans "buildtime" and "runtime." Up until now, we have been building images using `docker build .`, which is "buildtime." This is when our containers are actually built. We can think of "runtime" as what happens once our containers are built and being used.

Compose triggers "buildtime" -- instructing our images and containers to build -- but it also populates data used at "runtime," such as env vars and volumes. This is important to be clear on. For instance, when we add things like `volumes` and `command`, they will override the same things that may have been set up via the Dockerfile at "buildtime."

Open your `docker-compose.yml` file in your editor and copy/paste the following lines:

```yaml
version: '2'
services:
  web:
    build: .
    command: npm run dev
    volumes:
      - .:/usr/app/
      - /usr/app/node_modules
    ports:
      - "3000:3000"
    depends_on:
      - postgres
    environment:
      DATABASE_URL: postgres://todoapp@postgres/todos
  postgres:
    image: postgres:9.6.2-alpine
    environment:
      POSTGRES_USER: todoapp
      POSTGRES_DB: todos
```

This will take a bit to unpack, but let's break it down by service.

### The web service

The first directive in the web service is to `build` the image based on our `Dockerfile`. This will recreate the image we used before, but it will now be named according to the project we are in, `nodejsexpresstodoapp`. After that, we are giving the service some specific instructions on how it should operate:

*   `command: npm run dev` - Once the image is built, and the container is running, the `npm run dev` command will start the application.
*   `volumes:` - This section will mount paths between the host and the container.
*   `.:/usr/app/` - This will mount the root directory to our working directory in the container.
*   `/usr/app/node_modules` - This will mount the `node_modules` directory to the host machine using the buildtime directory.
*   `environment:` - The application itself expects the environment variable `DATABASE_URL` to run. This is set in `db.js`.
*   `ports:` - This will publish the container's port, in this case `3000`, to the host as port `3000`.

The `DATABASE_URL` is the connection string. `postgres://todoapp@postgres/todos` connects using the `todoapp` user, on the host `postgres`, using the database `todos`.

### The Postgres service

Like the NodeJS image we used, the Docker Store has a prebuilt image for [PostgreSQL](https://store.docker.com/images/022689bf-dfd8-408f-9e1c-19acac32e57b?tab=description). Instead of using a `build` directive, we can use the name of the image, and Docker will grab that image for us and use it. In this case, we are using `postgres:9.6.2-alpine`. We could leave it like that, but it has `environment` variables to let us customize it a bit.

`environment:` - This particular image accepts a couple environment variables so we can customize things to our needs. `POSTGRES_USER: todoapp` - This creates the user `todoapp` as the default user for PostgreSQL. `POSTGRES_DB: todos` - This will create the default database as `todos`.

## Running The Application

Now that we have our services defined, we can build the application using `docker-compose up`. This will show the images being built and eventually starting. After the initial build, you will see the names of the containers being created:

```bash
Pulling postgres (postgres:9.6.2-alpine)...
9.6.2-alpine: Pulling from library/postgres
627beaf3eaaf: Pull complete
e351d01eba53: Pull complete
cbc11f1629f1: Pull complete
2931b310bc1e: Pull complete
2996796a1321: Pull complete
ebdf8bbd1a35: Pull complete
47255f8e1bca: Pull complete
4945582dcf7d: Pull complete
92139846ff88: Pull complete
Digest: sha256:7f3a59bc91a4c80c9a3ff0430ec012f7ce82f906ab0a2d7176fcbbf24ea9f893
Status: Downloaded newer image for postgres:9.6.2-alpine
Building web
...
Creating nodejsexpresstodoapp_postgres_1
Creating nodejsexpresstodoapp_web_1
...
web_1       | Your app is running on port 3000
```

At this point, the application is running, and you will see log output in the console. You can also run the services as a background process, using `docker-compose up -d`. During development, I prefer to run without `-d` and create a second terminal window to run other commands. If you want to run it as a background process and view the logs, you can run `docker-compose logs`.

At a new command prompt, you can run `docker-compose ps` to view your running containers. You should see something like the following:

```bash
            Name                            Command              State           Ports
------------------------------------------------------------------------------------------------
nodejsexpresstodoapp_postgres_1   docker-entrypoint.sh postgres   Up      5432/tcp
nodejsexpresstodoapp_web_1        npm run dev                     Up      0.0.0.0:3000->3000/tcp
```

This will tell you the name of the services, the command used to start it, its current state, and the ports. Notice `nodejsexpresstodoapp_web_1` has listed the port as `0.0.0.0:3000->3000/tcp`. This tells us that you can access the application using `localhost:3000/todos` on the host machine.

```bash
/> curl localhost:3000/todos

[]
```

The `package.json` file has a script to automatically build the code and migrate the schema to PostgreSQL. The schema and all of the data in the container will persist as long as the `postgres:9.6.2-alpine` image is not removed.

Eventually, however, it would be good to check how your app will build with a clean setup. You can run `docker-compose down`, which will clear things that are built and let you see what is happening with a fresh start.

Feel free to check out the source code, play around a bit, and see how things go for you.

## Testing the Application

The application itself includes some integration tests built using [`jest`](https://facebook.github.io/jest/). There are various ways to go about testing, including creating something like `Dockerfile.test` and `docker-compose.test.yml` files specific for the test environment. That's a bit beyond the current scope of this article, but I want to show you how to run the tests using the current setup.

The current containers are running using the project name `nodejsexpresstodoapp`. This is a default from the directory name. If we attempt to run commands, it will use the same project, and containers will restart. This is what we don't want.

Instead, we will use a different project name to run the application, isolating the tests into their own environment. Since containers are ephemeral (short-lived), running your tests in a separate set of containers makes certain that your app is behaving exactly as it should in a clean environment.

In your terminal, run the following command:

```bash
/> docker-compose -p tests run -p 3000 --rm web npm run watch-tests
```

You should see `jest` run through integration tests and wait for changes.

The `docker-compose` command accepts several [options](https://docs.docker.com/compose/reference/overview/), followed by a command. In this case, you are using `-p tests` to run the services under the `tests` project name. The command being used is [`run`](https://docs.docker.com/compose/reference/run/), which will execute a one-time command against a service.

Since the `docker-compose.yml` file specifies a port, we use `-p 3000` to create a random port to prevent port collision. The `--rm` option will remove the containers when we stop the containers. Finally, we are running in the `web` service `npm run watch-tests`.

## Conclusion

At this point, you should have a solid start using Docker Compose for local app development. In the next part of this series about using Docker Compose for NodeJS development, I will cover integration and deployments of this application using Codeship.

Is your team using Docker in its development workflow? If so, I would love to hear about what you are doing and what benefits you see as a result.