Jake Trent

Deploy Lerna Packages to Heroku

A way to deploy multiple packages in Lerna monorepo to Heroku.

Lerna Packages

Lerna is a project that allows you to manage multiple JavaScript projects in a a single monorepo.

The packages are stored in a packages/ directory. For our purposes, let’s say that we have this directory structure with 2 projects:

.
└── packages
    ├── api
    └── worker

Each of the separate projects’ files are all within api or worker project subdirectories.

Heroku Requirements

By default, Heroku has the expectation that your project’s metadata (ie, package.json) and how to run it (ie, Procfile) are going to be in the root directory of the git repo. With Lerna, this is not a workable expectation because we need to handle multiple projects in a single repo.

Setup Heroku App

But we’ll get there. Let’s start with the basic step of first setting up our Heroku application. You’d do this step for each project you want to deploy. For us, let’s follow the example of just the api project. Start with:

cd packages/api && heroku create myproject-api

Monorepo Buildpack

In Heroku, how a project builds is controlled by a buildpack. Luckily for us there are a couple buildpacks that others have built to support the monorepo/Lerna scenario.

The one that works best for me is heroku-buildpack-select-subdir. Set it as the buildpack on your api project:

heroku buildpacks:set -a myproject-api https://github.com/Pagedraw/heroku-buildpack-select-subdir

This buildpack allows Heroku to discover a project nested in a monorepo.

Per-project Buildpack

But we still need a buildpack to tell that nested project how to build. For instance, we have api which is a Node.js project. We need to set the buildpack for it to know how to install a runtime and pull down dependencies.

We can set the buildpack on the api project so that the parent select-subdir buildpack knows how to use it by running this command:

heroku config:add BUILDPACK='packages/api=https://github.com/heroku/heroku-buildpack-nodejs#v83' -a myproject-api

Setup Git Remote

Now the buildpacks are setup, and we’re getting ready to push our code to a Heroku git remote. Unfortunately, because of our monorepo layout, when we ran heroku create, we didn’t get a Heroku git remote setup for us automatically as we usually do. So we need to set that up ourselves:

heroku git:remote -a myproject-api

Push Code as Normal

Now we’re all set. We should be able to push our api code as we’d expect to in another codebase. But in this case, we’re doing it in style in a multi-project monorepo using Lerna:

git push heroku master

How do you handle deploying your Lerna monorepo projects?