build triggers

Different Types of Build Triggers in Jenkins with Real-Time Examples

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🔹 Poll SCM

Use Case: Automatically build when code changes are pushed to Git (without a webhook).

Scenario: You want Jenkins to check the Git repository every 5 minutes. If changes are detected, it should trigger a build.

1

Steps to demo

Go to your Jenkins job → Configure, scroll to Build Triggers, check ✅ Poll SCM.

2

In the Schedule box, enter:

H/5 * * * *

(This means: check every 5 minutes)

3

Save the job. Make a commit in your Git repo → push to the remote. Jenkins will poll every 5 minutes and run a build if it detects changes.

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🔹 Build Periodically

Use Case: Run builds at scheduled times (like cron jobs).

Scenario: You want to run a job every night at 1 AM to back up logs or run a report.

1

Jenkins job → Configure, under Build Triggers, check ✅ Build periodically.

2

Add schedule:

CopyEdit0 1 * * *

(This means: run at 1:00 AM every day)

3

Save → Wait for the scheduled time → Jenkins runs the job automatically.

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🔹 GitHub hook trigger for GITScm polling

Use Case: Trigger builds instantly when changes are pushed to GitHub.

Scenario: As soon as a developer pushes code to GitHub, Jenkins should run the job (faster than polling).

1

Jenkins job → Configure, under Build Triggers, check ✅ GitHub hook trigger for GITScm polling. Save the job.

2

Go to GitHub repo → Settings → Webhooks. Add a new webhook:

• Payload URL: http://<your-jenkins-url>/github-webhook/

• Content type: application/json

• Choose: Just the push event

3

Push a commit to GitHub → Jenkins job triggers instantly.

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🔹 Trigger builds remotely (with authentication token)

Use Case: Trigger Jenkins jobs from external systems (like scripts, other tools, or pipeline integrations).

Scenario: You want to run a job from a custom Python script using a Jenkins API call.

1

Jenkins job → Configure, check ✅ Trigger builds remotely, enter a token (e.g., mytoken123). Save.

2

URL format:

http://<jenkins-url>/job/<job-name>/build?token=mytoken123

3

Run from browser or CURL:

curl http://<jenkins-url>/job/<job-name>/build?token=mytoken123

Add a Token to a Jenkins Job

1

Login to Jenkins → Go to your Freestyle job or create a new one. Click Configure for that job.

2

Scroll down to Build Triggers section. Check ✅ Trigger builds remotely (e.g., from scripts).

3

In the Authentication Token field, enter a token like:

nginxCopyEditmysecrettoken123

Click Save.

Trigger the Build Using the Token

Now you can trigger this job remotely using a browser or script.

URL Format:

http://<jenkins-host>:<port>/job/<job-name>/build?token=<your-token>

Example: If your Jenkins is running on http://localhost:8080, job name is my-job, and token is mysecrettoken123, then:

http://localhost:8080/job/my-job/build?token=mysecrettoken123

Example CURL command from the original content:

curl -u "admin:1a2b3c4d5e6f7g" "http://44.223.61.165:8080/job/test-job/build?token=mytoken123"

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🔹 Build after other projects are built

Use Case: Chain jobs (Job A triggers Job B after success).

Scenario: You want to run a testing job only after the deployment job finishes.

1

Create two jobs: Job-A and Job-B.

2

Go to Job-B → Configure, under Build Triggers, check ✅ Build after other projects are built, enter: Job-A. Save.

3

Run Job-A → After completion, Job-B starts automatically.

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🔹 Parameterized Trigger (Advanced using plugins)

Use Case: Trigger another job and pass parameters.

Scenario: Job A deploys an app, and then Job B runs a test suite with environment as a parameter.

1

Install Parameterized Trigger Plugin.

2

Go to Job-A → Configure. Under Post-build Actions, choose Trigger parameterized build on other projects.

3

Enter job name: Job-B. Pass parameter: ENV=dev. Save and run → Job-B is triggered with ENV=dev.

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🔹 Scripted Trigger via Pipeline (Using triggers {} block in Jenkinsfile)

Scenario: You want to define triggers as code inside the Jenkinsfile.

Sample Jenkinsfile (from original content):

groovyCopyEditpipeline {
    triggers {
        pollSCM('H/5 * * * *')   // Equivalent to Poll SCM
    }
    agent any
    stages {
        stage('Build') {
            steps {
                echo 'Building...'
            }
        }
    }
}

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Teaching Tip

• Start with a Freestyle project.

• Show a simple job first (like printing date or echo "Build triggered").

• Gradually show one trigger at a time.

• Use GitHub + webhook + Poll SCM for real-world impact.

• Allow students to test triggering via CURL or Git push.

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Do you want a combined Jenkins demo job with all trigger types? I can generate it for you as a ready-made teaching package — say "Yes" and tell me whether you prefer a Freestyle job, a Pipeline (Jenkinsfile), or both.