Stop bundling bootstrap Ruby (#1481)

Since this buildpack is written in Ruby, it needs a Ruby installation
to be installed in order to run. As such, during buildpack compile, a
bootstrap Ruby is downloaded and installed.

As a performance optimisation, this bootstrap Ruby was vendored into
the buildpack archive published to the Buildpack Registry, via the
`[[publish.Vendor]]` entries in `buildpack.toml`. Since Ruby installs
are OS-specific, this meant bundling three copies of Ruby, even though
only one would ever be used. With the old build system this was still a
net benefit, since the official language buildpacks would be downloaded
in advance when a build worker first booted.

However, with the new build system architecture, the build system
workers are no longer booted en-mass in advance, but instead started
on demand. This means there is no worker idle time, and so speculative
downloading of possibly-needed assets no longer makes sense.

As such, the bundling of multiple copies of Ruby in the buildpack
registry archive has now been removed.

This not only makes non-Ruby builds faster (since they have no need
for a Ruby installation at all), but will also speed up Ruby builds,
since they'll only need to download one bootstrap Ruby (for their
specific stack), rather than a version for every stack.

GUS-W-16184923.

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## [Unreleased]
 
+- Stop bundling bootstrap Ruby for each stack inside the buildpack archive on the buildpack registry (https://github.com/heroku/heroku-buildpack-ruby/pull/1481)
 
 ## [v276] - 2024-07-09
 

bin/support/bash_functions.sh

@@ -11,7 +11,7 @@ curl_retry_on_18() {
 }
 
 # This function will install a version of Ruby onto the
-# system for the buidlpack to use. It coordinates download
+# system for the buildpack to use. It coordinates download
 # and setting appropriate env vars for execution
 #
 # Example:
@@ -25,7 +25,7 @@ curl_retry_on_18() {
 #
 # This function relies on the env var `$STACK` being set. This
 # is set in codon outside of the buildpack. An example of a stack
-# would be "cedar-14".
+# would be "heroku-24".
 install_bootstrap_ruby()
 {
   local bin_dir=$1
@@ -42,10 +42,7 @@ install_bootstrap_ruby()
 
   # The -d flag checks to see if a file exists and is a directory.
   # This directory may be non-empty if a previous compile has
-  # already placed a Ruby executable here. Also
-  # when the buildpack is deployed we vendor a ruby executable
-  # at this location so it doesn't have to be downloaded for
-  # every app compile
+  # already placed a Ruby executable here.
   if [ ! -d "$heroku_buildpack_ruby_dir" ]; then
     heroku_buildpack_ruby_dir=$(mktemp -d)
     # bootstrap ruby

buildpack.toml

@@ -2,8 +2,6 @@
 name = "Ruby"
 ruby_version = "3.1.6"
 
-[publish]
-
 [publish.Ignore]
 files = [
   "changelogs/",
@@ -15,15 +13,3 @@ files = [
   "hatchet.json",
   "hatchet.lock",
 ]
-
-[[publish.Vendor]]
-url = "https://heroku-buildpack-ruby.s3.us-east-1.amazonaws.com/heroku-20/ruby-3.1.6.tgz"
-dir = "vendor/ruby/heroku-20"
-
-[[publish.Vendor]]
-url = "https://heroku-buildpack-ruby.s3.us-east-1.amazonaws.com/heroku-22/ruby-3.1.6.tgz"
-dir = "vendor/ruby/heroku-22"
-
-[[publish.Vendor]]
-url = "https://heroku-buildpack-ruby.s3.us-east-1.amazonaws.com/heroku-24/amd64/ruby-3.1.6.tgz"
-dir = "vendor/ruby/amd64/heroku-24"

spec/helpers/config_spec.rb

@@ -7,33 +7,11 @@
     bootstrap_version = config["buildpack"]["ruby_version"]
     expect(bootstrap_version).to eq(LanguagePack::RubyVersion::BOOTSTRAP_VERSION_NUMBER)
 
-    urls = config["publish"]["Vendor"].map {|h| h["url"] if h["dir"] != "." }.compact
-    urls.each do |url|
-      expect(url.include?(bootstrap_version)).to be_truthy, "expected #{url.inspect} to include #{bootstrap_version.inspect} but it did not"
-    end
-
     expect(`ruby -v`).to match(Regexp.escape(LanguagePack::RubyVersion::BOOTSTRAP_VERSION_NUMBER))
 
     bootstrap_version = Gem::Version.new(LanguagePack::RubyVersion::BOOTSTRAP_VERSION_NUMBER)
     default_version = Gem::Version.new(LanguagePack::RubyVersion::DEFAULT_VERSION_NUMBER)
 
     expect(bootstrap_version).to be >= default_version
   end
-
-  it "doesn't contain unexpected entries" do
-    require 'toml-rb'
-    config = TomlRB.load_file("buildpack.toml")
-
-    urls = config["publish"]["Vendor"].map {|h| h["url"] if h["dir"] != "." }.compact
-    heroku_20 = urls.find_all {|url| url.include?("heroku-20") }
-    expect(heroku_20.length).to eq(1)
-
-    heroku_22 = urls.find_all {|url| url.include?("heroku-22") }
-    expect(heroku_22.length).to eq(1)
-
-    heroku_24 = urls.find_all {|url| url.include?("heroku-24") }
-    expect(heroku_24.length).to eq(1)
-
-    expect(urls.length).to eq(3)
-  end
 end