How to conditionally update a CI/CD job image? - docker

Question

I just got into the (wonderful) world of CI/CD and have working pipelines. They are not optimal, though.
The application is a dockerized website:
the source needs to be compiled by webpack and end up in dist
this dist directory is copied to a docker container
which is then remotely built and deployed
My current setup is quite naïve (I added some comments to show why I believe the various elements are needed/useful):
# I start with a small image
image: alpine
# before the job I need to have npm and docker
# the problem: I need one in one job, and the second one in the other
# I do not need both on both jobs but do not see how to split them
before_script:
- apk add --update npm
- apk add docker
- npm install
- npm install webpack -g
stages:
- create_dist
- build_container
- stop_container
- deploy_container
# the dist directory is preserved for the other job which will make use of it
create_dist:
stage: create_dist
script: npm run build
artifacts:
paths:
- dist
# the following three jobs are remote and need to be daisy chained
build_container:
stage: build_container
script: docker -H tcp://eu13:51515 build -t widgets-sentinels .
stop_container:
stage: stop_container
script: docker -H tcp://eu13:51515 stop widgets-sentinels
allow_failure: true
deploy_container:
stage: deploy_container
script: docker -H tcp://eu13:51515 run --rm -p 8880:8888 --name widgets-sentinels -d widgets-sentinels
This setups works bit npm and docker are installed in both jobs. This is not needed and slows down the deployment. Is there a way to state that such and such packages need to be added for specific jobs (and not globally to all of them)?
To make it clear: this is not a show stopper (and in reality not likely to be an issue at all) but I fear that my approach to such a job automation is incorrect.

Answer 1

You don't necessarily need to use the same image for all jobs. Let me show you one of our pipelines (partially) which does a similar thing, just with composer for php instead of npm:
cache:
paths:
- vendor/
build:composer:
image: registry.example.com/base-images/php-composer:latest # use our custom base image where only composer is installed on to build the dependencies)
stage: build dependencies
script:
- php composer.phar install --no-scripts
artifacts:
paths:
- vendor/
only:
changes:
- composer.{json,lock,phar} # build vendor folder only, when relevant files change, otherwise use cached folder form s3 bucket (configured in runner config)
build:api:
image: docker:18 # use docker image to build the actual application image
stage: build api
dependencies:
- build:composer # reference dependency dir
script:
- docker login -u gitlab-ci-token -p "$CI_BUILD_TOKEN" "$CI_REGISTRY"
- docker build -t $CI_REGISTRY_IMAGE:latest.
- docker push $CI_REGISTRY_IMAGE:latest
The composer base image contains all necessary packages to run composer, so in your case you'd create a base image for npm:
FROM alpine:latest
RUN apk add --update npm
Then, use this image in your create_dist stage and use image: docker:latest as image in the other stages.

Answer 2

As well as referncing different images for different jobs you may also try gitlab anchors which provides reusable templates for the jobs:
.install-npm-template: &npm-template
before_script:
- apk add --update npm
- npm install
- npm install webpack -g
.install-docker-template: &docker-template
before_script:
- apk add docker
create_dist:
<<: *npm-template
stage: create_dist
script: npm run build
...
deploy_container:
<<: *docker-template
stage: deploy_container
...

Answer 3

Try multistage builder, you can intermediate temporary images and copy generated content final docker image. Also, npm should be part on docker image, create one npm image and use in final docker image as builder image.