Installed gems not found by bundler when BUNDLE_PATH changed with Docker - ruby-on-rails

Question

I'm using docker to develop a rails application. The docker file looks like this:
FROM ruby:1.9.3
RUN apt-get update -qq && apt-get install -y build-essential libpq-dev vim
ENV APP_HOME /next-reg
RUN mkdir $APP_HOME
WORKDIR $APP_HOME
ENV BUNDLE_PATH /box
ADD . $APP_HOME
RUN gem install gem1.gem gem2.gem
COPY Gemfile Gemfile
COPY Gemfile.lock Gemfile.lock
RUN bundle install
As you can see I change the BUNDLE_PATH, this is because of an article showing how we can persist gem downloads. So that overtime when the docker cache gets warm, it re-bundles and takes FOREVER.
When I docker build it successfully installs the gems, then it fails to find them on bundle. Could someone give me a hand with persisting gems, installing my own gems, and getting it to work?
Before I changed the BUNDLE_PATH the build worked, it just re bundled frequently without changes to the gem file (because, I guess the docker image cache got warm).
My docker-compose is like this:
db:
image: postgres
volumes:
- ~/.docker-voumes/postgres/data:/var/lib/postgresql/data
# This is to hold and persist ruby gems, referenced in web and in web's dockerfile.
gem_files:
image: busybox
volumes:
- /box
web:
build: .
command: bundle exec rails s -p 3000 -b '0.0.0.0'
volumes:
- .:/next-reg
volumes_from:
- gem_files
ports:
- "3000:3000"
- "8000:8000"
links:
- db
env_file:
- .myenv.env

Answer 1

I think that there is a lack of GEM_HOME/GEM_PATH in your code.
GEM_HOME/GEM_PATH will be used by gem install xxx to install gems in a specific folder.
BUNDLE_PATH will be used by bundle install to install gems in a specific folder but not by gem install xx
To have a working system you should do :
FROM ruby:1.9.3
RUN apt-get update -qq && apt-get install -y build-essential libpq-dev vim
ENV APP_HOME /next-reg
RUN mkdir $APP_HOME
WORKDIR $APP_HOME
ENV BUNDLE_PATH /box
ENV GEM_PATH /box
ENV GEM_HOME /box
ADD . $APP_HOME
RUN gem install bundler
RUN gem install tzinfo -v 1.2.2
COPY Gemfile Gemfile
RUN bundle install
With this Gemfile :
source 'https://rubygems.org'
gem 'tzinfo', '1.2.2'
Wich will produce :
Step 11/13 : RUN gem install tzinfo -v 1.2.2
---> Running in 8a87fa54fa19
Successfully installed thread_safe-0.3.6
Successfully installed tzinfo-1.2.2
2 gems installed
---> 3c91d59bde8a
Removing intermediate container 8a87fa54fa19
Step 13/13 : RUN bundle install
---> Running in 20f1e4ec93b1
Don't run Bundler as root. Bundler can ask for sudo if it is needed, and
installing your bundle as root will break this application for all non-root
users on this machine.
Fetching gem metadata from https://rubygems.org/...
Fetching version metadata from https://rubygems.org/.
Resolving dependencies...
Rubygems 1.8.23.2 is not threadsafe, so your gems will be installed one at a time. Upgrade to Rubygems 2.1.0 or higher to enable parallel gem installation.
Installing rake 12.0.0
Using thread_safe 0.3.6
Using bundler 1.14.6
Using tzinfo 1.2.2
Bundle complete! 2 Gemfile dependencies, 4 gems now installed.
Bundled gems are installed into /box.
As you can see in the result output, the bundle install re-use the preloaded gems from gem install