Adding an R buildpack to my Ruby on Rails App

Questions / Help
1

I’m migrating from Heroku and my Rails app uses an R script to analyze some data.

On Heroku, I added https://github.com/virtualstaticvoid/heroku-buildpack-r.git to my Buildpacks section in the Settings tab.

What’s the equivalent step I need to take over here on Fly? I found the Buildpacks section of the docs but nothing I’ve tried has worked.

Thanks!

2

I’m not an expert on heroku or buildpacks, but (and don’t scream!) I know a thing or two about deploying Rails apps via Dockerfiles. dockerfile-generator is a Rails generator that will inspect your application and generate a dockerfile.

If what you are saying is that you shell out to an R script, that’s beyond what can be automatically detected and I’d need a hint. If you are willing to give it a try, by tomorrow-ish I could have something like the following working for you:

bin/rails generate dockerfile --add r-base

I was planning on adding that support in the next week or so, but I can do that next if you are interested.

3

I have a Rake task that includes this line:

task.rake

output, status = Open3.capture2(Rails.root.join("clusters.r").to_s, stdin_data: csv_input)

clusters.r

#!/usr/bin/env Rscript

library(readr)

data <- read_csv(file("stdin"))

all=c()

for (k in 2:5)

... and so on

This works on Heroku when I include the R buildpack I mentioned above. But when I try to run this on Fly, I get:

/usr/bin/env: 'Rscript': No such file or directory
rake aborted!
4

I have verified that once r-base-core is added to the Dockerfile, Rscript is available:

% fly ssh console -C Rscript
Connecting to fdaa:0:d445:a7b:ae:56cc:9309:2... complete
Usage: /path/to/Rscript [--options] [-e expr [-e expr2 ...] | file] [args]

--options accepted are
  --help              Print usage and exit
  --version           Print version and exit
  --verbose           Print information on progress
  --default-packages=list
                      Where 'list' is a comma-separated set
                        of package names, or 'NULL'
or options to R, in addition to --no-echo --no-restore, such as
  --save              Do save workspace at the end of the session
  --no-environ        Don't read the site and user environment files
  --no-site-file      Don't read the site-wide Rprofile
  --no-init-file      Don't read the user R profile
  --restore           Do restore previously saved objects at startup
  --vanilla           Combine --no-save, --no-restore, --no-site-file
                        --no-init-file and --no-environ

'file' may contain spaces but not shell metacharacters
Expressions (one or more '-e <expr>') may be used *instead* of 'file'
See also  ?Rscript  from within R
5

You’re a bit of a wizard! :slight_smile: I’m not sure how this would be possible, but if I could also define which additional packages to install along with Rscript, that would be helpful. For example, I have to install the “readr” package and all of its dependencies as well.

6

Is this the package you are looking for? Debian -- Details of package r-cran-readr in bullseye

What I’m suggesting is that you will be able to peruse the following: Debian -- List of sections in "bullseye" and add any of the packages you see there - and as many as you want. If you go to that page and click on “GNU R” you will see a long list of packages. And, yes, any package you select would include the list of dependencies.

Note: I’m not the wizard here. That credit goes to the Debian team.

7

It is ready to beta test. Functionally complete, docs and tests not yet implemented.

First remove any buildpacks from fly.toml.

Then install/update dockerfile-rails.

  • if this gem is not in your Gemfile already, run bundle add dockerfile-rails --optimistic --group development
  • if this gem is already in your Gemfile, run bundle update

Generate a Dockerfile with r-base-core:

bin/rails generate dockerfile --add r-base-core

The generator will remember packages that you have added, so if you want to add another package, run the command again. You can also specify --add multiple times on one command. If you add something you don’t want anymore, run again with --remove.

When ready, fly deploy.

Nothing against buildpacks - they are magic but opaque. Dockerfiles aren’t magic and very transparent/explicit.

Additional information can be found at the FAQ: Dockerfiles and fly.toml · Fly Docs - this page will be updated soon to document how to add and remove packages.