Flow of CI Pipeline

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1. Code Commit (Starting Point)

The CI pipeline starts when a developer writes code and pushes it to a version control system like Git.

What happens:

• Developer makes changes

• Runs basic checks locally

• Pushes code to Git repository (GitHub / GitLab / Bitbucket)

Why this matters:

• CI ensures every code change is tested automatically

• No waiting for manual builds

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2. Trigger the CI Pipeline

Once code is pushed, the CI tool (like Jenkins) detects the change.

How it triggers:

• Webhook from Git

• Poll SCM (not recommended)

• Manual trigger (for testing)

Result:

• A new CI job starts automatically

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3. Source Code Checkout

The pipeline pulls the latest code from the repository.

Actions:

• Clones the repo

• Checks out the correct branch (main, develop, feature branch)

Why:

• CI always works on fresh code

• Avoids local machine dependency

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4. Environment Setup

Before building, the pipeline prepares the environment.

Includes:

• Installing dependencies

• Setting up language runtime (Java, Node, Python)

• Loading environment variables

• Injecting credentials securely

Example:

• Node modules install

• Maven dependencies download

Purpose:

• Makes builds repeatable and consistent

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5. Build Stage

Now the actual build happens.

Examples:

• Java: mvn clean package

• React: npm run build

• Python: create package or artifact

Output:

• Build artifacts (JAR, WAR, ZIP, dist folder)

Why:

• Converts source code into deployable format

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6. Automated Testing

This is the core of CI.

Types of tests:

• Unit tests

• Integration tests

• Basic smoke tests

What happens:

• Tests run automatically

• Pipeline stops if any test fails

Why:

• Catches bugs early

• Prevents broken code from moving forward

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7. Code Quality & Security Checks (Optional but Strong)

Many teams add quality gates.

Includes:

• Static code analysis

• Code coverage checks

• Security scans

Tools:

• SonarQube

• ESLint

• Snyk

Purpose:

• Maintains code standards

• Reduces technical debt

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8. Artifact Versioning & Storage

After a successful build:

• Artifacts are versioned using build number or commit ID

• Stored in artifact repositories

Examples:

• Nexus

• Artifactory

• S3

Why:

• Traceability

• Rollback support

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9. Notifications

The pipeline sends build status to the team.

Examples:

• Slack message

• Email

• Git status update

Purpose:

• Immediate feedback

• Team visibility

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10. CI Pipeline End

At this point:

• Code is built

• Tested

• Verified

If all stages pass:

• CI pipeline succeeds

• Code is ready for CD (deployment)

If any stage fails:

• Pipeline stops

• Developer fixes the issue and pushes again

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CI Pipeline Flow in One Line

Code Commit → Trigger → Checkout → Setup → Build → Test → Quality Check → Artifact Store → Notify

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CI vs CD (Quick clarity)

• CI stops at build + test

• CD continues with deployment to staging or production

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Interview-Ready Summary

A CI pipeline automates code integration by building, testing, and validating every code change, ensuring fast feedback, high code quality, and stable software delivery