Genie.jl

The highly productive Julia web framework

View the Project on GitHub GenieFramework/Genie.jl

Deploying Genie apps with Heroku Buildpacks

This tutorial shows how to host a Julia/Genie app using a Heroku Buildpack.

Prerequesites

This guide assumes you have a Heroku account and are signed into the Heroku CLI. Information on how to setup the Heroku CLI is available here.

The application

In order to try the deployment, you will need a sample application. Either pick one of yours or clone this sample one, as indicated next.

All Steps (in easy copy-paste format):

Customize your HEROKU_APP_NAME to something unique:

HEROKU_APP_NAME=my-app-name

Clone a sample app if needed:

git clone https://github.com/milesfrain/GenieOnHeroku.git

Go into the app’s folder:

cd GenieOnHeroku

And create a Heroku app:

heroku create $HEROKU_APP_NAME --buildpack https://github.com/Optomatica/heroku-buildpack-julia.git

Push the newly created app to Heroku:

git push heroku master

Now you can open the app in the browser:

heroku open -a $HEROKU_APP_NAME

If you need to check the logs:

heroku logs -tail -a $HEROKU_APP_NAME

Steps with more detailed descriptions:

Select an app name

HEROKU_APP_NAME=my-app-name

This must be unique among all Heroku projects, and is part of the url where your project is hosted (e.g. https://my-app-name.herokuapp.com/).

If the name is not unique, you will see this error at the heroku create step.

Creating ⬢ my-app-name... !
 ▸    Name my-app-name is already taken

Clone an example project

git clone https://github.com/milesfrain/GenieOnHeroku.git
cd GenieOnHeroku

You may also point to your own project, but it must be a git repo.

A Procfile in the root contains the launch command to load your app. The contents of the Procfile for this project is this single line:

web: julia --project src/app.jl $PORT

You may edit the Procfile to point to your own project’s launch script. (for example src/my_app_launch_file.jl instead of src/app.jl), but be sure to take into account the dynamically changing $PORT environment variable which is set by Heroku.

If you’re deploying a standard Genie application built with Genie.newapp, the launch script will be bin/server. Genie will automatically pick the $PORT number from the environment.

Create a Heroku project

heroku create $HEROKU_APP_NAME --buildpack https://github.com/Optomatica/heroku-buildpack-julia.git

This creates a project on the Heroku platform, which includes a separate git repository.

This heroku repository is added to the list of tracked repositories and can be observed with git remote -v.

heroku  https://git.heroku.com/my-app-name.git (fetch)
heroku  https://git.heroku.com/my-app-name.git (push)
origin  https://github.com/milesfrain/GenieOnHeroku.git (fetch)
origin  https://github.com/milesfrain/GenieOnHeroku.git (push)

We are using a buildpack for Julia. This runs many of the common deployment operations required for Julia projects. It relies on the directory layout found in the example project, with Project.toml, Manifest.toml in the root, and all Julia code in the src directory.

Deploy your app

git push heroku master

This pushes your current branch of your local repo to the heroku remote repo’s master branch.

Heroku will automatically execute the commands described in the Julia buildpack and Procfile of this latest push.

You must push to the heroku master branch to trigger an automated deploy.

Open your app’s webpage

heroku open -a $HEROKU_APP_NAME

This is a convenience command to open your app’s webpage in your browser.

The webpage is: https://$HEROKU_APP_NAME.herokuapp.com/

For example: https://my-app-name.herokuapp.com/

View app logs

heroku logs -tail -a $HEROKU_APP_NAME

This is another convenience command to launch a log viewer that remains open to show the latest status of your app.

The println statements from Julia will also appear here.

Exit this viewer with Ctrl-C.

Logs can also be viewed from the Heroku web dashboard. For example: https://dashboard.heroku.com/apps/my-app-name/logs

Deploy app updates changes

To deploy any changes made to your app, simply commit those changes locally, and re-push to heroku.

<make changes>
git commit -am "my commit message"
git push heroku master