Change default process type host to IPv6 ::

IPv6 is the future. Here's some more context heroku/roadmap#40. Related heroku/ruby-getting-started#165
heroku · Nov 23, 2024 · 1de4345 · 1de4345
1 parent 8491520
commit 1de4345
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diff --git a/buildpacks/ruby/CHANGELOG.md b/buildpacks/ruby/CHANGELOG.md
@@ -7,6 +7,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Changed
+
+- Default process types defined by the Ruby buildpack now use IPv6 host `::` which is equivalent of IPv4 host `0.0.0.0`. This will only affect applications that do not define a `web` process type via the `Procfile` and [Procfile Cloud Native Buildpack](https://github.com/heroku/buildpacks-procfile). Those applications must make sure to update their configuration to bind to an IPv6 host. ([]())
+
+### Added
+
 - The buildpack now warns the user when environmental variables used in running the default process are not defined. ([#307](https://github.com/heroku/buildpacks-ruby/pull/307))
 
 ## [3.0.0] - 2024-05-17

diff --git a/buildpacks/ruby/src/steps/get_default_process.rs b/buildpacks/ruby/src/steps/get_default_process.rs
@@ -72,7 +72,7 @@ fn default_rack() -> Process {
             &[
                 "bundle exec rackup",
                 "--port \"${PORT:?Error: PORT env var is not set!}\"",
-                "--host \"0.0.0.0\"",
+                "--host \"::\"",
             ]
             .join(" "),
         ])
@@ -88,6 +88,7 @@ fn default_rails() -> Process {
                 "bin/rails server",
                 "--port \"${PORT:?Error: PORT env var is not set!}\"",
                 "--environment \"$RAILS_ENV\"",
+                "--binding \"::\"",
             ]
             .join(" "),
         ])

diff --git a/docs/application_contract.md b/docs/application_contract.md
@@ -61,9 +61,9 @@ Once an application has passed the detect phase, the build phase will execute to
         - We will delete the least recently used (LRU) files first. Detected via file mtime.
 - Process types:
   - Given an application with the `railties` gem:
-    - We will default the web process to `bin/rails server` while specifying `-p $PORT` and `-e $RAILS_ENV"`. Use the `Procfile` to override this default.
+    - We will default the web process to `bin/rails server` while specifying `--port $PORT`, `--environment $RAILS_ENV"` and an IPv6 host with `--binding "::"` (equivalent of IPv4 host `0.0.0.0`). Use the `Procfile` to override this default.
   - If `railties` gem is not found but `rack` gem is present and a `config.ru` file exists on root:
-    - We will default the web process to `rackup` while specifying `-p $PORT` and `-h 0.0.0.0`. Use the `Procfile` to override this default. .
+    - We will default the web process to `rackup` while specifying `--port $PORT` and IPv6 host with `--host "::"` (equivalent of IPv4 host `0.0.0.0`). Use the `Procfile` to override this default. .
 - Environment variable defaults - We will set a default for the following environment variables:
   - `JRUBY_OPTS="-Xcompile.invokedynamic=false"` - Invoke dynamic is a feature of the JVM intended to enhance support for dynamicaly typed languages (such as Ruby). This caused issues with Physion Passenger 4.0.16 and was disabled [details](https://github.com/heroku/heroku-buildpack-ruby/issues/145). You can override this value.
   - `RACK_ENV=${RACK_ENV:-"production"}` - An environment variable that may affect the behavior of Rack based webservers and webapps. You can override this value.