🏗 What is CI/CD?
Think of software development like running a factory:
- CI (Continuous Integration) = the assembly line that checks every part before it moves forward.
- CD (Continuous Delivery/Deployment) = the shipping system that delivers the finished product safely to customers.
🔹 Continuous Integration (CI) — the “build & test” stage
Goal: Make sure every code change works well with the existing system.
- Code is written by a developer and pushed to Git (GitHub/GitLab).
- CI server runs automatically:
- Pulls the latest code.
- Builds the application (compiles, bundles, etc.).
- Runs automated tests (unit tests, linting, security scans).
- Feedback:
- If something breaks → developer gets an alert immediately.
- If everything passes → code is ready to be merged.
👉 CI ensures that the main branch is always healthy.
🔹 Continuous Delivery (CD) — the “ready to ship” stage
Goal: Always have a version of the app that can be deployed to production on demand.
- After CI passes, the pipeline packages the app:
- Example: JAR file, Docker image, or ZIP bundle.
- It is stored in a safe place (artifact repo, container registry).
- It can be deployed to staging or production with one click (but not automatically).
🔑 There’s usually a manual approval before production.
👉 CD = “delivery ready” — every change is deployable at any time.
🔹 Continuous Deployment (also CD) — the “auto-ship” stage
Goal: Every change that passes CI goes straight to production without human approval.
- Same process as Continuous Delivery.
- But instead of waiting for a human, the pipeline deploys automatically.
- If problems are detected, monitoring/alerts trigger a rollback.
👉 Continuous Deployment = fully automated releases.
🚀 Simple Analogy
Imagine you run a bakery:
- CI = Every time a baker finishes a cake, it goes through a quality check (taste, size, decoration). If bad, it’s sent back immediately.
- Continuous Delivery = Good cakes are placed in a ready-to-ship box. The delivery van waits for your approval before going.
- Continuous Deployment = As soon as a cake is boxed, the delivery van drives off automatically.
🎯 Why CI/CD matters
- Catch bugs early (cheaper to fix).
- Faster releases → deploy many times a day if needed.
- More confidence → small changes = easier rollbacks.
- Less manual work → automation saves time.
✅ Summary
- CI = test every code change automatically.
- CD (Delivery) = app is always ready to deploy, usually requires human approval.
- CD (Deployment) = app is deployed automatically after passing tests.