Deploy Docker image on Heroku

Dockerfile

The most important file for docker image that defines instructions how to deploy an application. For this tutorial, I will be using a Angular project but this method can be applied to pretty much any node.js application. First create a Dockerfile in root directory of the project.

$ touch Dockerfile

Dockerfile instructions

For this project, I will be using node:14.1-alpine image as base image. Feel free to explore other docker images as well. Moving on, You can set node env as production with ENV command and move into directory by WORKDIR

Dockerfile

FROM node:14.1-alpine
ENV NODE_ENV=production
WORKDIR /app

Now, COPY the package.json and package-lock.json from root directory of project to root directory of /app. (because we WORKDIR into /app on 2nd step so we will use current directory symbol (.) ). Now installing node dependencies with production flag to ignore installing devDependencies. After COPYing all files from our angular project into docker image we can write CMD command which will execute the starting script of your application.

Dockerfile

FROM node:14.1-alpine
ENV NODE_ENV=production
WORKDIR /app
COPY package*.json ./
RUN npm install --production
COPY . .
CMD ["npm", "start"]

Dockerignore

Notice one step before CMD we copied all files into Docker image which includes node_modules folder as well. We can ignore node_modules just like .gitignore by creating .dockerignore file in the root directory of project.

.dockerignore

node_modules

Heroku setup

If your machine does not have Heroku CLI installed, you can download it from their official website. Create a new Heroku app through its cli and set stack to container.

$ heroku login
$ heroku create <your-app-name>
$ heroku stack:set container -a <your-app-name>

Uploading image to Heroku

At this point, we can push our project into heroku container and release it to finish deployment process.

$ heroku container:push web -a <your-app-name>
$ heroku container:release web -a <your-app-name>

Heroku logs

You can see rest of the logs by heroku logs command for your app. And that is it, your application is dockerized and should be accessible on your-app-name.herokuapp.com

$ heroku logs -t -a <your-app-name>