Ruby Builder for Heroku

This uses Docker to build MRI ruby binaries locally in a cedar image for the heroku ruby buildpack.

Building a Ruby

Assumptions

I'm assuming you've already setup Docker.

The directory layout used by this script inside the docker container is as follows:

• It builds the binary as tarball and puts it in /tmp/output.
• All the work is performed in a clean room /tmp/workspace.
• The artifacts downloaded for the build are put into /tmp/cache.
• Finally, the /app directory is there like in a normal cedarish app, so we'll prefix things within this directory so the load paths are useable and fast lookups when using the --enable-load-relative flag. We'll need special build rubies for ruby 1.9.2/1.8.7 since --enable-load-relative is broken there.

Stacks

This build tool supports heroku's multiple stacks. The built rubies will go in the builds/ directory. We also have a rubies/ directory for ensuring consistent builds. In each of these directories, they're split into a stack folder. All of the cedar-14 builds will be in builds/cedar-14/ for instance.

Building

First we'll need to generate the docker images needed for building the appropriate stack.

$ bundle exec rake generate_image[cedar-14]

Generate a ruby build script:

$ bundle exec rake new[2.2.2,cedar-14]

From here, we can now execute a ruby build:

$ bash rubies/cedar-14/ruby-2.2.2.sh

When it's complete you should now see builds/cedar-14/ruby-2.2.2.tgz.

If you set the env vars AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY, you can upload them to s3. By default, we upload to the heroku-buildpack-ruby s3 bucket.

$ bundle exec rake upload[2.2.2,cedar-14]

Support two stacks

When a new Ruby version releases you will want to build support for all stacks.

bundle exec rake new[2.6.0,heroku-18] && \
bash rubies/heroku-18/ruby-2.6.0.sh && \
bundle exec rake upload[2.6.0,heroku-18] && \
\
bundle exec rake test[2.6.0,heroku-18] && \
bundle exec rake new[2.6.0,heroku-16] && \
bash rubies/heroku-16/ruby-2.6.0.sh && \
bundle exec rake upload[2.6.0,heroku-16] && \
bundle exec rake test[2.6.0,heroku-16] && \
\
bundle exec rake new[2.6.0,cedar-14] && \
bash rubies/cedar-14/ruby-2.6.0.sh && \
bundle exec rake upload[2.6.0,cedar-14] && \
bundle exec rake test[2.6.0,cedar-14] && \
\
echo "Done building 2.6.0 for cedar-14, heroku-16, and heroku-18"

Building a GIT_URL release

Sometimes a version might need to be tested, for example a commit on Ruby trunk.

If you're building from a specific commit, then fork ruby/ruby to your own repo.

To build it first generate a new file:

bundle exec rake new[2.6.0,heroku-18]

Then add in the destination to the GIT_URL:

docker run -v $OUTPUT_DIR:/tmp/output -v $CACHE_DIR:/tmp/cache -e VERSION=2.6.0 -e GIT_URL=https://github.com/schneems/ruby#schneems/bundler -e STACK=heroku-18 hone/ruby-builder:heroku-18

If you need to use a branch you can put it in the url after the #.

Docker Enviroment Variables

To configure the build, we use environment variables. All of them are listed below:

• VERSION - This is the ruby version being used. It's expected to be in the format: "#{MAJOR}.#{MINOR}.#{TEENY}-p#{PATCH}". This option is required.
• BUILD - If this flag is set (can be set to anything for true), then hammer-ruby will build a "build" ruby. This sets the prefix to "/tmp/ruby-#{MAJOR}.#{MINOR}.#{TEENY}". This is required for ruby 1.8.7 and 1.9.2 since the --enable-load-relative flag does not work properly. --enable-load-relative allows a ruby to be executed from anywhere and not just the prefix directory. By required, you need to build two binaries: one where BUILD is false (runtime ruby) and where BUILD is true (build ruby).
• DEBUG - If this flag is set (can be set to anything for true), then hammer-ruby will set debug flags in the binary ruby being built.
• RUBYGEMS_VERSION - This allows one to specify the Rubygems version being used. This is only required for Ruby 1.8.7 since it doesn't bundle Rubygems with it.
• GIT_URL - If this option is used, it will override fetching a source tarball from http://ftp.ruby-lang.org/pub/ruby with a git repo. This allows building ruby forks or trunk. This option also supports passing a treeish git object in the URL with the # character. For instance, git://github.com/hone/ruby.git#ruby_1_8_7.
• S3_BUCKET_NAME - This option is the S3 bucket name containing of dependencies for building ruby. If this option is not specified, hammer-ruby defaults to "heroku-buildpack-ruby". The dependencies needed are libyaml-0.1.4.tgz and libffi-3.0.10.tgz.
• JOBS - the number of jobs to run in parallel when running make: make -j<jobs>. By default this is 2.

How it works

There is a script build.rb that was coppied over when the docker container was built. This can be seen in the various Dockerfile.* files.