How to cache deployment image in gitlab-ci? - docker

Question

I'm creating a gitlab-ci deployment stage that requires some more libraries than existing in my image. In this example, I'm adding ssh (in real world, I want to add many more libs):
image: adoptopenjdk/maven-openjdk11
...
deploy:
stage: deploy
script:
- which ssh || (apt-get update -y && apt-get install -y ssh)
- chmod 600 ${SSH_PRIVATE_KEY}
...
Question: how can I tell gitlab runner to cache the image that I'm building in the deploy stage, and reuse it for all deployment runs in future? Because as written, the library installation takes place for each and every deployment, even if nothing changed between runs.

Answer 1

GitLab can only cache files/directories, but because of the way apt works, there is no easy way to tell it to cache installs you've done this way. You also cannot "cache" the image.
There are two options I see:
Create or use a docker image that already includes your dependencies.
FROM adoptopenjdk/maven-openjdk11
RUN apt update && apt install -y foo bar baz
Then build/push the image the image to dockerhub, then change the image: in the yaml:
image: membersound/maven-openjdk11-with-deps:latest
OR simply choose an image that already has all the dependencies you want! There are many useful docker images out there with useful tools installed. For example octopusdeploy/worker-tools comes with many runtimes and tools installed (java, python, AWS CLI, kubectl, and much more).
attempt to cache the deb packages and install from the deb packages. (beware this is ugly)
Commit a bash script as so to a file like install-deps.sh
#!/usr/bin/env bash
PACKAGES="wget jq foo bar baz"
if [ ! -d "./.deb_packages" ]; then
apt update && apt --download-only install -y ${PACKAGES}
cp /var/cache/apt/archives/*.deb ./.deb_packages
fi
apt install -y ./.deb_packages/*.deb
This should cause the debian files to be cached in the directory ./.deb_packages. You can then configure gitlab to cache them so you can use them later.
my_job:
before_script:
- install-deps.sh
script:
- ...
cache:
paths:
- ./.deb_packages