CI/CD for Monorepos
Explore strategies for optimizing CI/CD pipelines in monorepos, including selective job execution based on changed files.
CI/CD for Monorepos is a free DevOps Bootcamp lesson on CoddyKit — lesson 1 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the DevOps Bootcamp learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.
What's a Monorepo?
A monorepo is a single repository that holds the code for many projects or applications. Instead of having separate repositories for each service or library, everything lives together.
Think of it like a big library with many books (projects) in one building (repository), rather than a separate building for each book. This approach has its pros and cons, especially for CI/CD.
Monorepo CI/CD Challenges
While monorepos offer benefits like easier code sharing, they can pose challenges for Continuous Integration/Continuous Delivery (CI/CD) pipelines:
- Slow Builds: If every change triggers a full build and test suite for *all* projects, pipelines become very slow.
- Resource Waste: Unnecessarily running unrelated jobs consumes build minutes and resources.
- Developer Frustration: Long feedback loops can slow down development velocity.
The Need for Selective CI/CD
The key to efficient monorepo CI/CD is selectivity. We want our pipelines to be smart enough to:
- Identify *what* has changed.
- Run CI/CD jobs *only* for the projects affected by those changes.
This approach saves time, reduces resource consumption, and provides faster feedback to developers.
Triggering by Paths: `on.paths`
GitHub Actions provides a powerful way to achieve selectivity using the paths filter in your workflow triggers. You can specify directories or files that, when changed, should trigger a workflow.
If a file outside these paths changes, the workflow won't run. This is perfect for monorepos!
on:
push:
branches:
- main
paths:
- 'apps/frontend/**'
- 'libs/shared/**'Paths Filter in Action
Here's a simple workflow that only runs when changes are pushed to files within the apps/backend directory or a specific README.md file.
This ensures only relevant tests or builds are triggered for your backend service.
name: Backend CI
on:
push:
branches:
- main
paths:
- 'apps/backend/**'
- 'README.md'
jobs:
build-backend:
runs-on: ubuntu-latest
steps:
- uses: actions/checkout@v4
- name: Build backend app
run: echo "Building backend..."Ignoring Paths: `paths-ignore`
Sometimes you want a workflow to run for *most* changes, but skip it if only certain files are modified (e.g., documentation, log files). The paths-ignore filter is perfect for this.
It works similarly to paths but specifies files that should *not* trigger the workflow.
on:
pull_request:
branches:
- main
paths-ignore:
- 'docs/**'
- '**/*.md'Dynamic Selective Runs with `git diff`
For more complex logic, you can use Git commands like git diff within your workflow steps to dynamically check for changes. This allows you to build custom conditions.
For example, you might check if changes occurred in a specific folder and set an output variable to decide if a subsequent job should run.
Conditional Job Execution Example
This workflow step uses git diff to see if any files under apps/api/ have changed between the current commit and the base branch. If they have, it sets an output variable api_changed to 'true'.
This output can then control whether a 'deploy API' job runs.
jobs:
check-changes:
runs-on: ubuntu-latest
outputs:
api_changed: ${{ steps.diff.outputs.api_changed }}
steps:
- uses: actions/checkout@v4
- name: Check API changes
id: diff
run: |
if git diff --quiet ${{ github.event.before }} ${{ github.sha }} -- apps/api/;
then
echo "api_changed=false" >> $GITHUB_OUTPUT
else
echo "api_changed=true" >> $GITHUB_OUTPUT
fi
deploy-api:
needs: check-changes
if: needs.check-changes.outputs.api_changed == 'true'
runs-on: ubuntu-latest
steps:
- name: Deploy API
run: echo "Deploying API..."Monorepo Structure for CI/CD
An organized monorepo structure greatly simplifies selective CI/CD. Grouping related files and projects into well-defined directories makes it easy to use paths filters effectively.
/apps/frontend/apps/backend/libs/shared/docs
Clear separation allows for precise targeting of workflows.
Monorepo CI/CD Quiz
Optimizing CI/CD for monorepos is crucial for maintaining developer velocity and efficient resource usage. Consider what strategies best address the challenges of a large, consolidated codebase.
Recap & Next Steps
You've learned how to tackle CI/CD challenges in monorepos by implementing selective job execution. Using GitHub Actions' paths filters and advanced git diff techniques, you can ensure your pipelines run only what's necessary.
This leads to faster feedback, reduced costs, and a smoother development experience. Keep exploring how to fine-tune your workflows for even greater efficiency!
Frequently asked questions
Is the “CI/CD for Monorepos” lesson free?
Yes — the full text of “CI/CD for Monorepos” is free to read here on the web, and the DevOps Bootcamp course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the DevOps Bootcamp course, upgrade to CoddyKit PRO.
What will I learn in “CI/CD for Monorepos”?
Explore strategies for optimizing CI/CD pipelines in monorepos, including selective job execution based on changed files. You practise DevOps Bootcamp with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start DevOps Bootcamp?
No prior experience is required. DevOps Bootcamp on CoddyKit is structured for beginners through advanced learners; this is — lesson 1 of 4, so you can start here or from the beginning and move at your own pace.
How long does the “CI/CD for Monorepos” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this DevOps Bootcamp lesson?
Yes. Every DevOps Bootcamp lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.