NodeJS Buildpack on App Platform

App Platform is a Platform-as-a-Service (PaaS) offering that allows developers to publish code directly to DigitalOcean servers without worrying about the underlying infrastructure.


How App Platform Builds Images

App Platform supports two ways to build an image for your app: Cloud Native Buildpacks and Dockerfiles.

When you give App Platform access to your code, it defaults to using a Dockerfile if one is present in the root of the directory or specified in the app spec. Otherwise, App Platform checks your code to determine what language or framework it uses. If it supports the language or framework, it chooses an appropriate resource type and uses the proper buildpack to build the app and deploy a container.

heroku-buildpack-nodejs is utilized as the buildpack for detecting and building your NodeJS applications.

NodeJS Applications using Buildpacks

App Platform looks for any of the following files to detect a NodeJS application:

  • package.json
  • package-lock.json
  • yarn.lock

If both package-lock.json and yarn.lock exist, Yarn is preferred.

Specifying Versions

You can customize the Node version used by specifying the version in the engines section of your package.json:

{
  "engines": {
    "node": "14.x"
  }
}

You can customize the NPM version used by specifying the version in the engines section of your package.json:

{
  "engines": {
    "npm": "~1.0.20"
  }
}

You can customize the Yarn version used by specifying the version in the engines section of your package.json:

{
  "engines": {
    "yarn": "^0.14.0"
  }
}

Caching

The buildpack automatically caches and re-uses the node_modules directory between builds. After the package manager’s install command is run (yarn install or npm install), the node_modules directory is stored in the build cache along with snapshot of the package manager’s lockfile. In subsequent builds, the cached node_modules directory will be restored only if the lockfile’s contents are identical to cached version. Otherwise, the cache will be discarded.

Clearing the Cache

If your app is failing to build and you suspect that the issue is related to node_modules caching, you can force clear the cache and start a new build. To do this in the control panel, navigate to your app, click the Actions menu, and then select Force Build and Deploy.

Force Build and Deploy screen with Clear Build Cache checked

In the Force Build and Deploy window, select the Clear Build Cache option, and then click on the “Deploy” button. This clears the build cache and starts a new deployment.

Here’s an example with Node and Express that uses the PORT variable or 3000 for developing locally.

const express = require('express');
const app = express();

// get our port
const port = process.env.PORT || 3000;

// applicaton code goes here

// have node listen on our port
app.listen(port, () => console.log(`App listening on port ${port}!`));