由于 ruby-buildpack + bundler，部署到 dokku 失败？

Question

I'm deploying a rails app to dokku. The Versions are:

• ruby 3.1.2
• bundler 2.3.26 (on my development machine)
• gem 3.3.22 (on my development machine)

when i try to deploy to dokku, the heroku ruby buildpack is used, and I get the following output:

-----> Ruby app detected
-----> Installing bundler 2.2.21
-----> Removing BUNDLED WITH version in the Gemfile.lock
-----> Compiling Ruby/Rails
-----> Using Ruby version: ruby-3.1.2
-----> Installing dependencies using bundler 2.2.21
       Running: BUNDLE_WITHOUT='development:test' BUNDLE_PATH=vendor/bundle BUNDLE_BIN=vendor/bundle/bin BUNDLE_DEPLOYMENT=1 bundle install -j4
       [330, #<Thread:0x00007fc0e8b43c90 run>, #<NameError: uninitialized constant Gem::Source
       (defined?(@source) && @source) || Gem::Source::Installed.new
       ^

The crazy thing: I have another app with the same configuration where it works:

-----> Ruby app detected
-----> Installing bundler 2.2.21
-----> Removing BUNDLED WITH version in the Gemfile.lock
-----> Compiling Ruby/Rails
-----> Using Ruby version: ruby-3.1.2
-----> Installing dependencies using bundler 2.2.21
       Running: BUNDLE_WITHOUT='development:test' BUNDLE_PATH=vendor/bundle BUNDLE_BIN=vendor/bundle/bin BUNDLE_DEPLOYMENT=1 bundle install -j4
       Fetching gem metadata from https://rubygems.org/.........

My research so far:

This seems to be the problem described here as an issue with bundler 2.3.7 first described in February 2022. But my buildpack uses bundler 2.2.21, so it should not be affected?

The newest ruby-buildpack from heroku seems to have been released in 2021? Can this be right?

This fixed the problem for one app:

• upgrade to ruby 3.1.3 (by editing ruby version in Gemfile and in .ruby-version )
• bundle install
• bundle lock --add-platform x86_64-linux

After one successfull install I could also roll back to the old ruby version, before upgrade, and successfully install that.

How? Why? What is going on here?

Now another app that used to work stopped working.

Answer 1

Purging the dokku build cache fixed the problem:

dokku repo:purge-cache