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Migrating Existing R Applications

This guide is for migrating existing R applications which make use of the heroku-buildpack-r on Heroku.

Follow these steps to migrate your R application to use the Heroku container stack.

NOTE: Docker is not required to be installed on your machine, unless you need to build and run the images locally. For the most common use cases, you will probably use the default setup, so it won't be necessary to have docker installed.

Shiny Applications

These steps are for Shiny applications.

In your Shiny application source's root directory:

  • Create a Dockerfile file and insert the following content.

    FROM ghcr.io/virtualstaticvoid/heroku-docker-r:shiny
ENV PORT=8080
CMD ["/usr/bin/R", "--no-save", "--gui-none", "-f", "/app/run.R"]

  • Create a heroku.yml file and insert the following content.

    build:
  docker:
    web: Dockerfile

  • Commit the changes, using git as per usual.

    git add Dockerfile heroku.yml
git commit -m "Using heroku-docker-r FTW"

  • Create the Heroku application with the container stack

    heroku create --stack=container

    Or configure an existing application to use the container stack.

    heroku stack:set container

  • Deploy your application to Heroku, replacing <branch> with your branch. E.g. master.

    git push heroku <branch>

  • Scale the web dyno

    heroku scale web=1

See heroku-docker-r-shiny-app for an example application.

Plumber Applications

These steps are for Plumber applications.

In your Plumber application source's root directory:

  • Create a Dockerfile file and insert the following content.

    FROM ghcr.io/virtualstaticvoid/heroku-docker-r:plumber
ENV PORT=8080
CMD ["/usr/bin/R", "--no-save", "--gui-none", "-f", "/app/app.R"]

  • Create a heroku.yml file and insert the following content.

    build:
  docker:
    web: Dockerfile

  • Commit the changes, using git as per usual.

    git add Dockerfile heroku.yml
git commit -m "Using heroku-docker-r FTW"

  • Create the Heroku application with the container stack

    heroku create --stack=container

    Or configure an existing application to use the container stack.

    heroku stack:set container

  • Deploy your application to Heroku, replacing <branch> with your branch. E.g. master.

    git push heroku <branch>

  • Scale the web dyno

    heroku scale web=1

See heroku-docker-r-plumber-app for an example application.

Other R Applications

These steps are for console and other types of R applications.

In your R application source's root directory:

  • Create a Dockerfile file and insert the following content.

    FROM ghcr.io/virtualstaticvoid/heroku-docker-r:build
CMD ["/usr/bin/R", "--no-save", "-f", "/app/<R-program>"]

    Change <R-program> to be the main R program you want to have executed, or change it to just run the R console for interactive use. E.g. CMD ["/usr/bin/R", "--no-save"].

  • Create a heroku.yml file and insert the following content.

    build:
  docker:
    app: Dockerfile

  • Commit the changes, using git as per usual.

    git add Dockerfile heroku.yml
git commit -m "Using heroku-docker-r FTW"

  • Create the Heroku application with the container stack

    heroku create --stack=container

    Or configure an existing application to use the container stack.

    heroku stack:set container

  • Deploy your application to Heroku, replacing <branch> with your branch. E.g. master.

    git push heroku <branch>

  • Run the application

    heroku run app

Multi-Buildpack Applications

For R applications which make use of multiple buildpacks, this is not supported nor needed on the container stack.

You will need to refactor your setup to include the components, which those buildpacks provided, in the Dockerfile if possible.

Details on this are out of the scope of this document, as there are too many permutations possible.

Slug Compilation

During the slug compilation phase of the Heroku deploy on the container stack, you will notice that the build output is now different. It shows the docker build instructions and outputs as the image is being built.

During this phase your init.R file is executed, to typically install and configure any R packages you require, as it did before with the R buildpack.

If you have provided an Aptfile in your application directory then those packages will be installed during this process.

Furthermore, if you use packrat or renv to manage your R package dependencies, then you can elect to do away with your init.R if all it was doing was installing packages :-).

This is an example of the output during compilation:

$ git push heroku master

Counting objects: 9, done.
Delta compression using up to 8 threads.
Compressing objects: 100% (6/6), done.
Writing objects: 100% (9/9), 2.17 KiB | 1.08 MiB/s, done.
Total 9 (delta 0), reused 0 (delta 0)
remote: Compressing source files... done.
remote: Building source:
remote: === Fetching app code
remote: Sending build context to Docker daemon  9.216kB
remote: Step 1/5 : FROM ghcr.io/virtualstaticvoid/heroku-docker-r:build
remote: build: Pulling from ghcr.io/virtualstaticvoid/heroku-docker-r
remote: d3938036b19c: Pulling fs layer
...
remote: 817da545be2b: Waiting
...
remote: a9b30c108bda: Verifying Checksum
remote: a9b30c108bda: Download complete
...
remote: d3938036b19c: Pull complete
...
remote: Digest: sha256:a88020addc2f8b80e674eb169e09c5b02bf1da169b6fcaef02b87b059fd38164
remote: Status: Downloaded newer image for virtualstaticvoid/heroku-docker-r:build
remote: # Executing build triggers...
...
remote: Step 1/1 : COPY . /app
remote: Step 1/1 : RUN if [ -f "/app/init.R" ]; then /usr/bin/R --no-init-file --no-save --slave -f /app/init.R; fi;
remote:  ---> Running in b8ec7dab059a
remote: Step 1/1 : RUN if [ -f "/app/packrat/init.R" ]; then /usr/bin/R --no-init-file --no-save --slave -f /app/packrat/init.R --args --bootstrap-packrat; fi;
remote:  ---> Running in f15cfb28f0c6
...
remote: Successfully built 9a5ca146f496
remote: Successfully tagged a4d0f4b97ebe88c0e65264081366350647bfc9b6:latest
remote: a0638673a463: Preparing
remote: 3d3996739656: Waiting
remote: 3f8b58dc539d: Pushed
remote: Verifying deploy... done.
To https://git.heroku.com/xyz-abc-12345.git
 * [new branch]      master -> master

Troubleshooting

  • If you are using a Procfile, then you will need to change the arguments of the CMD directive in the Dockerfile to be the same as that in your Procfile. Alternatively, you can provide run directives in the heroku.yml file, to match your Procfile. See the heroku.yml documentation for further details.
  • Any fakechroot, fakeroot and chroot command prefixes are no longer needed and must be removed.
  • The container's file system layout follows the same convention as that of the R buildpack, so your application files will be located in the /app directory.