Reuse gems from previous version

[leomao10]

I noticed that every time I run gcloud app deploy, bundle install will be execute, and it will refeching gems and install them again, even the ruby version and Gemfile.lock are not updated.

Wondering if there is a way for us to reuse the gems we fetched before, so that it can speed up the deployments.

[RSpace]

+1

[leomao10]

I can do it via cloud build by adding following docker file in my repo as ruby-base.dockerfile:

# This file is generated base on generate-dockerfile from follow repo:
# https://github.com/GoogleCloudPlatform/ruby-docker/tree/master/ruby-generate-dockerfile

ARG ruby_version=2.6.4
ARG prebuilt_image=gcr.io/gcp-runtimes/ruby/ubuntu16/prebuilt/ruby-2.6.4:latest
FROM $prebuilt_image as prebuilt-ruby

FROM gcr.io/gcp-runtimes/ruby/ubuntu16:latest AS augmented-base
ARG ruby_version=2.6.4
ARG bundler_version=2.0.2
ARG rails_env=production

## Commonly installed gems (e.g. bundler) are available from this image.
COPY --from=gcr.io/gcp-runtimes/ruby/ubuntu16/build-tools:latest /opt/gems/ /opt/gems/

## Install Ruby ${ruby_version} from a prebuilt image. If a prebuilt image
## is not available, use the alternate installation method commented below.
COPY --from=prebuilt-ruby \
 /opt/rbenv/versions/${ruby_version} \
 /opt/rbenv/versions/${ruby_version}

RUN echo "This is the ruby version ${ruby_version}"
RUN rbenv global $ruby_version \
 && rbenv rehash \
 && (gem install /opt/gems/bundler-${bundler_version}.gem ; \
 rbenv rehash);

## Alternate installation for Ruby versions that have no prebuilt image.
# RUN if [ ! -x ${RBENV_ROOT}/versions/${ruby_version}/bin/ruby ]; \
# then \
# cd ${RBENV_ROOT}/plugins/ruby-build \
# && git pull \
# && rbenv install -s ${ruby_version} \
# && rbenv global ${ruby_version} \
# && rbenv rehash \
# && (gem install /opt/gems/bundler-${bundler_version}.gem ; \
# rbenv rehash); \
# fi

COPY ./Gemfile /app/
COPY ./Gemfile.lock /app/

RUN bundle install --deployment && rbenv rehash

ENTRYPOINT []

Then in cloudbuild.yml file, I added this step:

 - name: 'gcr.io/cloud-builders/docker'
 id: preinstall-gems
 entrypoint: 'bash'
 args:
 - '-c'
 - |
 docker build -t gcr.io/${PROJECT_ID}/ruby-base/${COMMIT_SHA} \
 --file ruby-base.dockerfile \
 --build-arg ruby_version=$(cat .ruby-version) \
 --build-arg prebuilt_image=gcr.io/gcp-runtimes/ruby/ubuntu16/prebuilt/ruby-$(cat .ruby-version):latest \
 .
 docker push gcr.io/${PROJECT_ID}/ruby-base/${COMMIT_SHA}
 
 # Generate dockerfile for app engine
 - name: 'gcr.io/gcp-runtimes/ruby/ubuntu16/generate-dockerfile'
 id: generate-dockerfile
 env: [
 'PROJECT_ID=${PROJECT_ID}'
 ]
 args: [
 '--base-image','gcr.io/${PROJECT_ID}/ruby-base/${COMMIT_SHA}:latest',
 '--build-tools-image', 'gcr.io/gcp-runtimes/ruby/ubuntu16/build-tools:latest'
 ]

 # Build docker image for app engine
 - name: 'gcr.io/cloud-builders/gcloud'
 id: deploy-appengine
 entrypoint: /bin/bash
 args:
 - '-c'
 - |
 gcloud config set app/cloud_build_timeout 1200
 gcloud app deploy ./app.yaml ${_TRAFFIC}
 waitFor: ['generate-dockerfile', 'preinstall-gems']
 timeout: 1200s
timeout: 1200s

[leomao10]

But of course, we still reinstall the gems when Gemfile.lock is not changed. Might need to take idea from this blogpost for yarn cache:
https://medium.com/hackernoon/using-yarn-with-docker-c116ad289d56