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Overview

GitHub webhooks enable automatic triggering of the Jenkins CI/CD pipeline whenever code is pushed to the repository. This eliminates the need to manually start builds and ensures continuous integration.

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How Webhooks Work

When you push code to your GitHub repository:
  1. GitHub sends an HTTP POST request to your Jenkins server
  2. Jenkins receives the webhook payload
  3. Jenkins automatically starts the pipeline defined in the Jenkinsfile
  4. The pipeline executes all stages (Clone, Build, Test, Deploy)

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Prerequisites

Before configuring webhooks, ensure:
  • Jenkins is running on a publicly accessible server (e.g., AWS EC2)
  • Jenkins has the GitHub plugin installed
  • Your Jenkins server accepts incoming connections on the webhook port

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GitHub Webhook Configuration

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Step 1: Navigate to Repository Settings

  1. Go to your GitHub repository: https://github.com/mani-6666/Jenkins-Pipeline-for-CI-CD
  2. Click on Settings
  3. In the left sidebar, click Webhooks
  4. Click Add webhook

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Step 2: Configure Webhook Settings

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Payload URL
string
required
The Jenkins webhook endpoint URL.Format: http://<your-jenkins-server-ip>:8080/github-webhook/Example: http://54.123.45.67:8080/github-webhook/
Make sure to include the trailing slash (/) at the end of the URL.
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Content type
string
default:"application/json"
The format of the webhook payload.Select: application/json
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Secret
string
Optional: A secret token for validating webhook requests.Leave blank or configure a secret token for added security.
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Which events would you like to trigger this webhook?
string
default:"Just the push event"
Select the events that should trigger the Jenkins pipeline.Recommended: Just the push eventOptions:
  • Just the push event (recommended for CI/CD)
  • Send me everything
  • Let me select individual events
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Active
boolean
default:true
Enable the webhook immediately after creation.Keep this checked to activate the webhook.

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Step 3: Save Webhook

Click Add webhook to save your configuration.

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Jenkins Configuration

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Install Required Plugins

Ensure these plugins are installed in Jenkins:
  1. GitHub Integration Plugin
  2. Pipeline Plugin
  3. Docker Plugin
To install plugins:
  1. Go to Manage Jenkins > Manage Plugins
  2. Search for the required plugins
  3. Install and restart Jenkins if needed

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Configure Jenkins Job

  1. Create a new Pipeline job in Jenkins
  2. Under Build Triggers, enable:
    • GitHub hook trigger for GITScm polling
  3. In Pipeline section, configure:
    • Definition: Pipeline script from SCM
    • SCM: Git
    • Repository URL: https://github.com/mani-6666/Jenkins-Pipeline-for-CI-CD.git
    • Branch: */main
    • Script Path: Jenkinsfile

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Testing the Webhook

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Test Push Event

  1. Make a change to your repository (e.g., update README.md)
  2. Commit and push to the main branch:
git add .
git commit -m "Test webhook trigger"
git push origin main
  1. Check Jenkins dashboard - the pipeline should start automatically
  2. View the build logs to verify all stages execute successfully

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Verify Webhook Delivery

  1. Go to GitHub repository Settings > Webhooks
  2. Click on your webhook
  3. Scroll to Recent Deliveries
  4. Check for successful delivery (green checkmark)
  5. Click on a delivery to view:
    • Request headers and payload
    • Response from Jenkins

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Troubleshooting

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Webhook Not Triggering

  • Verify Jenkins is publicly accessible
  • Check firewall rules on your server
  • Ensure port 8080 is open for incoming connections
  • Verify the payload URL is correct with trailing slash
  • Check Recent Deliveries in GitHub webhook settings
  • Review the response code and error message
  • Verify Jenkins is running and accessible
  • Check Jenkins logs: /var/log/jenkins/jenkins.log
  • Verify GitHub hook trigger for GITScm polling is enabled
  • Check Jenkins job configuration
  • Ensure the branch name matches (e.g., main vs master)
  • Review Jenkins system logs for errors

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Security Considerations

If your Jenkins server is publicly accessible, consider:
  • Enabling authentication for Jenkins
  • Using webhook secret tokens for validation
  • Restricting IP access to known GitHub webhook IPs
  • Using HTTPS instead of HTTP for webhook URLs

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Pipeline Execution Flow

Once the webhook triggers the pipeline, the following stages execute automatically: 
// 1. Clone Stage
git branch: 'main', url: 'https://github.com/mani-6666/Jenkins-Pipeline-for-CI-CD.git'

// 2. Build Stage
docker build -t nodejs-demo-app:latest .

// 3. Test Stage
npm install
npm test

// 4. Deploy Stage
docker run --name Jenkins -d -p 80:3000 nodejs-demo-app:latest

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Accessing the Deployed Application

After successful pipeline execution:
  • Access your application at: http://<your-ec2-public-ip>
  • The app runs on port 80 (mapped from internal port 3000)
  • Check Jenkins console output for deployment confirmation

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