Triggering Jenkins Jobs

Ways to Trigger a Jenkins Job

A Jenkins job can be triggered either manually or automatically. There are three common automatic triggers:

1. GitHub Webhook
2. Build Periodically
3. Poll SCM

1. WebHooks

Whenever a developer commits code, the change is automatically applied on the server — this is achieved using WebHooks.

Setting up a webhook from GitHub

Repository → Settings → Webhooks → Add webhook

• Payload URL: jenkinsURL:8080/github-webhook/
• Content type: application/json
• Click Add webhook

Then, in Jenkins: Job → Configure → Build Triggers → check "GitHub hook trigger for GITScm polling" → Save.

2. Build Periodically

Job → Configure → Build Periodically. This runs on CRON syntax.

The cron format has 5 stars: * * * * *

• 1st star → minutes
• 2nd star → hours (24-hour format)
• 3rd star → date
• 4th star → month
• 5th star → day of the week (Sunday=0, Monday=1 ... Saturday=6)

Example: Aug 28, 11:30 AM, Sunday build → 30 11 28 08 0

* * * * * means a build every single minute. */5 * * * * means every 5 minutes. For reference, use the website crontab.guru.

Note: with Build Periodically, the build happens on schedule whether the code changed or not.

3. Poll SCM

Also based on cron syntax, but only runs a build if there's an actual change in the GIT repo within that window.

Quick Comparison

Trigger	Behaviour	Scope
Webhooks	Build happens the instant a commit is pushed	Only works with GIT/GitHub
Poll SCM	Checks periodically, builds only if changes exist	Only works with GIT
Build Periodically	Builds on a fixed schedule 24x7, regardless of changes	Works for any DevOps tool, not just Git