How to write .gitlab-ci.yml to build/deploy with conditions - gitlab

Question

I am new to CI/CD and Gitlab. I have a CI/CD script to test, build and deploy and I use 2 branches and 2 EC2. My goal is to have a light and not redundant script to build and deploy my changes in functions of the branch.
Currently my script looks like this but after looking the Gitlab doc I saw many conditionals keywords like rules but I'm really lost about how I can use conditional format in my script to optimise it.
Is there a way to use condition and run some script if there is a merge from a branch or from an other? Thanks in advance!
#image: alpine
image: "python:3.7"
before_script:
- python --version
stages:
- test
- build_staging
- build_prod
- deploy_staging
- deploy_prod
test:
stage: test
script:
- pip install -r requirements.txt
- pytest Flask_server/test_app.py
only:
refs:
- develop
build_staging:
stage: build_staging
image: node
before_script:
- npm install -g npm
- hash -d npm
- nodejs -v
- npm -v
script:
- cd client
- npm install
- npm update
- npm run build:staging
artifacts:
paths:
- client/dist/
expire_in: 30 minutes
only:
refs:
- develop
build_prod:
stage: build_prod
image: node
before_script:
- npm install -g npm
- hash -d npm
- nodejs -v
- npm -v
script:
- cd client
- npm install
- npm update
- npm run build
artifacts:
paths:
- client/dist/
expire_in: 30 minutes
only:
refs:
- master
deploy_staging:
stage: deploy_staging
image: registry.gitlab.com/gitlab-org/cloud-deploy/aws-base:latest # gitlab image for awc cli commands
before_script:
- apt-get update
# - apt-get -y install python3-pip
# - apt-get --assume-yes install awscli
- apt-get --assume-yes install -y shellcheck
script:
- shellcheck .ci/deploy_aws_STAGING.sh
- chmod +x .ci/deploy_aws_STAGING.sh
- .ci/deploy_aws_STAGING.sh
- aws s3 cp client/dist/ s3://......./ --recursive
only:
refs:
- develop
deploy_prod:
stage: deploy_prod
image: registry.gitlab.com/gitlab-org/cloud-deploy/aws-base:latest # gitlab image for awc cli commands
before_script:
- apt-get update
# - apt-get -y install python3-pip
# - apt-get --assume-yes install awscli
- apt-get --assume-yes install -y shellcheck
script:
- shellcheck .ci/deploy_aws_PROD.sh
- chmod +x .ci/deploy_aws_PROD.sh
- .ci/deploy_aws_PROD.sh
- aws s3 cp client/dist/ s3://........../ --recursive
only:
refs:
- master

Answer 1

Gitlab introduces rules for includes with version 14.2
include:
- local: builds.yml
rules:
- if: '$INCLUDE_BUILDS == "true"'

Answer 2

A good pattern as your cicd grows in complexity is to use includes and extend keywords. For example you could implement the following in your root level .gitlab-ci.yml file:
# best practice is to pin to a specific version of node or build your own image to avoid surprises
image: node:12
# stages don't need an environment appended to them; you'll see why in the included file
stages:
- build
- test
- deploy
# cache node modules in between jobs on a per branch basis like this
cache:
key: ${CI_COMMIT_REF_SLUG}
paths:
- .npm/
# include other definitions
includes:
- './ci-templates/.foo-app-ci.yml'
Then in another folder (or even another repository) you can include other templates. I didn't fully refactor this out for you but I hope this gives you the idea of not only how to use a rule to trigger your job but also how you can start to make reusable snippets and build on them to reduce the overall complexity. See the yaml comments for guidance on why I did things a certain way. example .foo-app-ci.yml file
# this script was repeated so define it once and reference it via anchor
.npm:install: &npm:install
- npm ci --cache .npm --prefer-offline # to use the cache you'll need to do this before installing dependencies
- cd client
- npm install
- npm update
# you probably want the same rules for each stage. define once and reuse them via anchor
.staging:rules: &staging:rules
- if: $CI_COMMIT_TAG
when: never # Do not run this job when a tag is created manually
- if: $CI_COMMIT_BRANCH == 'develop' # Run this job when commits are pushed or merged to the develop branch
.prod:rules: &prod:rules
- if: $CI_COMMIT_TAG
when: never # Do not run this job when a tag is created manually
- if: $CI_COMMIT_BRANCH == $CI_DEFAULT_BRANCH # Run this job when commits are pushed or merged to the default branch
# many parts of the build stage were repeated; define it once and lets extend from it
.build:template: &build:template
stage: build
before_script:
- &npm:install
artifacts:
paths:
- client/dist/
expire_in: 30 minutes
# many parts of the deploy stage were repeated; define it once and lets extend from it
.deploy:template: &deploy:template
stage: deploy
image: registry.gitlab.com/gitlab-org/cloud-deploy/aws-base:latest # gitlab image for awc cli commands
before_script:
- apt-get update
- apt-get --assume-yes install -y shellcheck
# here we extend from the build template to run the staging specific build
build:staging:
extends: *build:template
environment: staging
script:
- npm run build:staging
rules:
- *staging:rules
# this is kind of an oddball... not used to seeing python to test a node app. we're not able to reuse as much here
test:staging:
image: "python:3.7"
stage: test
script:
- pip install -r requirements.txt
- pytest Flask_server/test_app.py
rules:
- *staging:rules # apply staging rules to trigger test stage
needs:
- job: build:staging # normally we want to build before test; this will trigger test after the build
# here we extend from the build template to run the prod specific build
build:prod:
extends: *build:template
environment: prod
script:
- npm run build
rules:
- *prod:rules
# same thing for the deploy phases... extend from the deploy template for env specific requirements
deploy:staging:
extends: *deploy:template
script:
- shellcheck .ci/deploy_aws_STAGING.sh
- chmod +x .ci/deploy_aws_STAGING.sh
- .ci/deploy_aws_STAGING.sh
- aws s3 cp client/dist/ s3://......./ --recursive
rules:
- *staging:rules
needs:
- job: build:staging
artifacts: true
deploy:prod:
extends: *deploy:template
script:
- shellcheck .ci/deploy_aws_PROD.sh
- chmod +x .ci/deploy_aws_PROD.sh
- .ci/deploy_aws_PROD.sh
- aws s3 cp client/dist/ s3://........../ --recursive
rules:
- *prod:rules
needs:
- job: build:prod
artifacts: true
I would start basic and as you start to get comfortable with a working pipeline you can experiment with further enhancements and breaking out into more fragments. Hope this helps!