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Troubleshooting Node.js Deploys

Last updated 01 November 2018

Your Node.js deploy failed - now what? Start with these simple steps to troubleshoot a build issue.

Check your buildpack

Are you using the officially supported and maintained buildpack, or something else? Most of the time, the standard buildpack is the best choice - either alone, or paired with other buildpacks (like Ruby).

Find out by running:

$ heroku buildpacks

To use the official buildpack:

$ heroku buildpacks:set heroku/nodejs

Compare Node and npm Versions

Your production environment should mirror your development environment, especially in the case of important binaries. First, check your local versions:

$ node --version
$ npm --version

Then, compare the results with your package.json engines section. You are specifying a node version, right?

You can see which binaries Heroku is using on each deploy in the build logs, which look something like this:

remote: -----> Installing binaries
remote:        Resolving node version 10.x...
remote:        Downloading and installing node 10.3.0...
remote:        Using default npm version: 6.4.1

They should match up with the same versions you saw locally. If they don’t, you should specify the matching versions in your package.json.

Don’t check in generated directories

Your app’s node_modules directory is generated at build time from the dependencies listed in package.json. Therefore, node_modules (and other generated directories like bower_components) shouldn’t be included in source control. It’s easy to check:

$ git ls-files | grep node_modules

If you see a list of results, then you should instruct git to stop tracking node_modules:

$ echo "node_modules" >> .gitignore
$ git rm -r --cached node_modules
$ git commit -am 'untracked node_modules'

Instead of committing node_modules directly into your repository, you can ensure exact versions via npm’s shrinkwrap or by using the --save-exact flag:

$ npm install express --save --save-exact

Ensure you aren’t relying on untracked dependencies

When you npm install a module, that module is saved to your project’s node_modules directory but not to the package.json file that describes your project’s dependencies. This means that your project will work on your machine, but as soon as you try to share it elsewhere it will fail with missing dependencies.

Instead, install locally with npm install --save foobar. That will automatically record the installation to your package.json dependencies list.

For the same reason, you should avoid installing global dependencies (npm install -g foobar). Use --save instead to put binaries in myproject/node_modules/.bin, keeping them local and trackable.

Here’s how to check whether or not you’re relying on commonly-installed global modules:

$ which bower
$ which grunt
$ which gulp

If any of these show a path, your project may depend on a binary outside of its local directory, leading to a case of, “but it works on my machine!”

If you’ve added these modules to package.json, but they still aren’t installing, be sure that you’ve added them to the correct list. In Production (NPM_CONFIG_PRODUCTION=true), ‘devDependencies’ won’t be installed, so anything you need in production should be moved to 'dependencies,’ or production mode should be disabled:

$ heroku config:set NPM_CONFIG_PRODUCTION=false

For a full example, check out Building Node.js Apps with Grunt.

Start with a blank slate

Each time you run npm install, npm leaves packages that meet your semver requirements untouched. That’s why an npm install today may lead to a different tree than the npm install you ran yesterday, even if your package.json didn’t change.

Therefore, it’s a good practice to periodically clear node_modules and reinstall from scratch to ensure that your package.json dependencies are still valid:

$ rm -rf node_modules
$ npm install --quiet --production
$ npm start

In fact, those are essentially the commands that Heroku runs when we build and launch your project. If they work locally, you’re likely to be cloud-ready.

Alternatively, you can add yarn or npm-shrinkwrap to your workflow to lock down dependency versions so that they are consistent from install to install. This is the best practice for production environments.

Check for differences between development and production

Many Node applications have checks that will perform different logic based on the value of the NODE_ENV environment variable. This is especially common when building web assets to avoid the overhead minifying JavaScript and compressing images during development.

Occasionally this can lead to subtle bugs that will only show up when trying to deploy. If you run into a new bug while deploying check to see if it can be reproduced locally by setting NODE_ENV to production.

$ NODE_ENV=production npm start

Check your .gitignore

A required file may exist locally, but it’s possible to accidentally prevent it from being included in your git repo by an overly broad rule in your .gitignore file.

As an example, you might wish to exclude a lib directory at the root of your application, but the rule:

lib/

in your .gitignore will recursively match any subdirectory named lib, so the file js/library-name/lib/index.js would not be included in your git repo. You can fix this case by moving the slash to the front, which will only match the lib directory in the application root directory.

/lib

Open a ticket

If none of these solutions work for you, open a ticket with Heroku so we can help.