CI/CD in a nutshell
Continuos Integration
Integration means adding new code to the shared codebase
What does it mean to do that continously?
Version Control
- The code needs to be in version control.
These days that means git
- Roll back when something is wrong
- Work independently on a shared codebase
- A record of who has done what
Test
- All tests are run automatically
- New code can't break tests
- You still need to write the tests! 😉
Lint
It is common to have a linter setup - a utility that checks codestyle, formatting etc.
This ensures that the code is formatted consistently across multiple developers
Review
After tests are green and linters have passed, another developer gives a code review.
Reviews are focused on logic and implementation
Build
Take the approved code and package it into an artifact, pushing it to some artifact storage
Continous Integration
Continous Integration has three goals
- Quick feedback
- Rapid integration of new code into the main codebase
- ...while ensuring high quality through automatic testing and linting
Continous Delivery
Continous Delivery is making sure that code is always in a releasable state.
The CD part of the pipeline is in charge of taking the artifact and deploying to an environment
Quick Aside - Definitions
Artifact
The packaged code that is the result of our CI step
Deploying
Releasing the artifact into a given environment
Environment
A set of services and their configuration. Isolated from each other, so they don’t share resources
Configuration
A setting that changes how the artifact operates.
In one environment, the GDPR masking setting might be turned on and another might have it turned off.
Same artifact - different behaviour depending on configuration
Read more at https://12factor.net/
Deployment vs Delivery
- Continous Deployment is having code that's always shippable
- Continous Delivery is always shipping code
Most implement Continous Deployment - a pipeline that is able to deploy a given artifact to a given environment
Deploying
What deploying means is different from project to project
- Upload a binary to a homepage
- Publish a package to a package index
- Copy code to a webserver
- Create a Kubernetes release
CICD Services
There are many vendors in this space
Jenkins
- Is open source
- Written in Java
- Tons of plugins
- Groovy syntax
Gitlab CI/CD
- Pioneered Repo -> CICD integration
- Tied to Gitlab
- YAML syntax
Github Actions
- The new kid on the block
- Uses Node.js / Docker containers
- Tied to Github
- YAML syntax
Bamboo
- Integrated with Bitbucket
- Written in Java
- Has a limited subset in YAML
Git workflow
To best use CI/CD, we often combine it with a standardized git workflow.
This helps write CI/CD pipelines that match the intentions when using git
Git flow
Each type of branch has a meaning
Main branch
Is always in a releasable state - should only be merged into when ready to release
Develop
Contains the newest features being worked on - the basis for new features
Feature branch
When starting work on a new feature we create a feature branch starting from develop.
This is the main unit of work - every bit of new code starts as a feature branch and is merged back into develop when done, through a Pull Request.
When the feature branch is merged, it should be deleted
Release
When we are ready to release, we create a release branch and run through the release checklist.
for example:
- Update versions
- Update any version references
- Merge into master and develop.
- Tag master with the version number and push tags
CI/CD is often set up to run deployment if it’s a tagged commit