[SOLVED] How to Trigger a Jenkins Build When a New Tag is Released? - jenkins

[SOLVED] Easy Ways to Trigger a Jenkins Build When a New Tag is Released

In the field of continuous integration and delivery, triggering a Jenkins build when we release a new tag is very important for developers and teams. It helps us automate our deployment processes. This guide will show us different ways to set up Jenkins to react to new tag events. This way, our software will always be up-to-date with the latest changes. We will also talk about best practices for setting up these triggers and some tips for troubleshooting.

Here are the solutions we will talk about in this chapter:

Part 1 - Configure GitHub Webhook for Tag Events: We will learn how to set up a webhook in GitHub. This webhook will trigger a Jenkins build when we create a new tag.
Part 2 - Set Up Jenkins Job to Poll for Tags: We will find out how to set up a Jenkins job to check regularly for new tags in our repository.
Part 3 - Use Git Tag Trigger Plugin in Jenkins: We will explore the Git Tag Trigger plugin. This plugin makes it easier to trigger builds based on tags.
Part 4 - Create a Custom Script to Handle Tag Events: We will understand how to write a custom script that listens for tag events and triggers a Jenkins build when needed.
Part 5 - Integrate with GitLab for Tag Releases: We will see how to set up a similar integration using GitLab. This will help us trigger Jenkins builds on tag releases.
Part 6 - Utilize Jenkins Pipeline for Tag Detection: We will learn how to create a Jenkins pipeline that can detect and respond to tag events.
Frequently Asked Questions: We will answer common questions about triggering Jenkins builds on tag releases.

By the end of this chapter, we will know how to automate our Jenkins builds in response to new tag releases. This will help improve our development workflow. For more information, we can check these resources: How can I trigger Jenkins builds? and How to set up Jenkins CI with Git?.

Part 1 - Configure GitHub Webhook for Tag Events

We want to trigger a Jenkins build when we release a new tag in our GitHub repository. To do this, we need to set up a webhook in GitHub. This webhook will send messages to Jenkins. Here are the steps to follow:

Navigate to Your GitHub Repository:
- First, we go to our repository on GitHub.
- Next, we click on “Settings”.
Add a Webhook:
- On the left side, we select “Webhooks”.
- Then we click on “Add webhook”.
Configure the Webhook:
- Payload URL: We enter our Jenkins URL with the correct job and token if we use one. For example:
```
http://<your-jenkins-url>/github-webhook/
```
- Content type: We select application/json.
- Secret: We can set a secret for more security if we want.
- Events: We choose “Let me select individual events” and check the “Release” option. This includes events for creating tags.
Save the Webhook:
- We click on “Add webhook” to save our settings.
Verify the Webhook:
- After we save, GitHub sends a ping event to check the webhook. We can look at the “Recent Deliveries” section to see if it was successful.

Now, our Jenkins setup will listen for tag events from GitHub. For more help with Jenkins, we can see how to trigger Jenkins builds based on these events.

Part 2 - Set Up Jenkins Job to Poll for Tags

We can trigger a Jenkins build when a new tag is released. To do this, we need to set up our Jenkins job to check for tags in our Git repository. Here are the steps we will follow:

Create a New Job:
- We go to the Jenkins dashboard.
- We click on “New Item.”
- We choose “Freestyle project” and give our job a name.
Configure Source Code Management:
- In the job settings, we select “Git” in the Source Code Management section.
- We enter our repository URL.
- We add the credentials if we need them.
Set Up Polling:
- We scroll down to the “Build Triggers” section.
- We check the box for “Poll SCM.”
- In the Schedule field, we enter a cron expression to say how often Jenkins should check for new tags. For example, to check every 5 minutes, we use:
```
H/5 * * * *
```
Specify Branch Specifier for Tags:
- In the “Branches to build” field, we enter:
```
refs/tags/*
```
  This will make sure Jenkins looks at all tags in the repository.
Add Build Steps:
- In the “Build” section, we add our build steps (like Execute Shell or Invoke Ant) to tell Jenkins what to do when it finds a new tag.
Save the Configuration:
- We click on “Save” to keep the changes.

Now our Jenkins job is ready to check for new tags. When a new tag is made in our Git repository, Jenkins will start a build based on our polling schedule.

For more details on how to trigger Jenkins builds, we can look at this guide.

Part 3 - Use Git Tag Trigger Plugin in Jenkins

We can trigger a Jenkins build when we release a new tag by using the Git Tag Trigger Plugin. This plugin helps Jenkins to react to tag events in our Git repository. It will start a build automatically when a tag is created.

Installation of the Git Tag Trigger Plugin

Open Jenkins Dashboard.
Go to Manage Jenkins then Manage Plugins.
In the Available tab, search for Git Tag Trigger Plugin.
Click on the plugin and choose Install without restart.

Configuration of the Plugin

Create or change a Jenkins job.
In the job settings page, scroll down to Build Triggers section.
Check the box for “Trigger builds remotely (e.g., from scripts)” and set a token like tag-trigger.
In the Source Code Management section, pick Git and enter your repository URL.
Under Branches to build, use this format to specify tags:
```
refs/tags/*
```

Setting Up Webhook in GitHub

Go to the settings of your GitHub repository.
Click on Webhooks then Add webhook.
Set the Payload URL to your Jenkins server URL followed by /github-webhook/ (like http://your-jenkins-url/github-webhook/).
Choose application/json for the content type.
In the section Which events would you like to trigger this webhook?, select Let me select individual events. and check Create for tags.
Save the webhook.

Example of Triggering a Build

After we finish the setup, pushing a new tag to our GitHub repository will trigger the Jenkins job automatically. We can check the Jenkins job console output to see the build.

For more information on triggering builds, you can look at this detailed guide.

Part 4 - Create a Custom Script to Handle Tag Events

We can trigger a Jenkins build when we release a new tag. To do this, we need to create a custom script. This script will listen for tag events and trigger the Jenkins job. We can use a simple webhook and a script that processes incoming requests.

Step 1: Create a Webhook in Your Git Repository

Go to the settings of your Git repository.
Find the “Webhooks” section.
Add a new webhook with these details:
- Payload URL: http://<your-jenkins-server>/git/notifyCommit?url=<your-repo-url>
- Content type: application/json
- Which events would you like to trigger this webhook?: Choose “Just the push event” or “Let me select individual events” and check “Tag push events”.

Step 2: Custom Script to Handle the Incoming Payload

Next, we will create a script to handle the incoming payload. Here is a simple Python script:

import json
import requests
from flask import Flask, request

app = Flask(__name__)

@app.route('/tag_event', methods=['POST'])
def tag_event():
    data = request.json
    if 'ref' in data and data['ref'].startswith('refs/tags/'):
        tag_name = data['ref'].split('/')[-1]
        trigger_jenkins_build(tag_name)
    return '', 204

def trigger_jenkins_build(tag_name):
    jenkins_url = 'http://<your-jenkins-server>/job/<your-job-name>/buildWithParameters'
    params = {'TAG_NAME': tag_name}
    response = requests.post(jenkins_url, params=params)
    print(f'Jenkins build triggered for tag: {tag_name}, Response: {response.status_code}')

if __name__ == '__main__':
    app.run(host='0.0.0.0', port=5000)

Step 3: Deploy the Script

Make sure Python and Flask are installed on our server.
Save the script as tag_listener.py.
Run the script:
```
python tag_listener.py
```

Step 4: Configure Jenkins Job

In Jenkins, create or change your job to accept parameters.
Add a string parameter named TAG_NAME. We will use this to get tag information from the webhook.

Testing the Setup

Push a new tag to your repository. Check if the Jenkins build is triggered.
Make sure the webhook is set up correctly. It should point to your script’s endpoint.

For more help on integrating Jenkins with tags, check out this tutorial.

Part 5 - Integrate with GitLab for Tag Releases

We want to trigger a Jenkins build when we release a new tag in GitLab. To do this, we need to set up a webhook in our GitLab repository that points to our Jenkins server. Let’s follow these steps to connect GitLab with Jenkins for tag releases:

Create a Jenkins Job:
- First, we go to our Jenkins dashboard.
- Next, we create a new Freestyle project or a Pipeline project.
- In the job settings, we find the “Build Triggers” section. Here, we select “Trigger builds remotely (e.g., from scripts)” and set an auth token like gitlab-trigger.
Set Up GitLab Webhook:
- Now, we go to our GitLab repository and click on Settings then Webhooks.
- In the URL box, we enter:
```
http://<your-jenkins-url>/project/<your-job-name>?token=gitlab-trigger
```
- We choose the Trigger option for “Tag push events”.
- If our Jenkins server uses HTTPS, we can turn on SSL verification.
- Finally, we click Add webhook.
Test the Webhook:
- To test, we need to push a new tag to our GitLab repository. We can do this with the command:
```
git tag v1.0.0
git push origin v1.0.0
```
- After that, we check our Jenkins job to see if it started successfully.
Configure Job to Build on Tags:
- In the Jenkins job settings, we look at the “Source Code Management” section. Here, we make sure “Branches to build” is set to */tags/*. This way, it will build only on tag events.
Verify Build Trigger:
- After pushing a new tag, we can confirm that the Jenkins build was started by checking the build history in Jenkins.

For more information on triggering Jenkins jobs, we can visit this link. This setup helps us automate our CI/CD pipeline easily each time we create a new tag in GitLab.

Part 6 - Use Jenkins Pipeline for Tag Detection

We can trigger a Jenkins build when a new tag is released by using a Jenkins Pipeline. This helps us define our CI/CD process in code. It makes it easier to manage and keep track of changes. Here is a simple guide to set up a Jenkins Pipeline for tag detection.

Create a Jenkinsfile: We should place the Jenkinsfile in the root of our repository. This file will show the pipeline stages. One of the stages will check for new tags.

pipeline {
    agent any
    triggers {
        pollSCM('H/5 * * * *') // Check every 5 minutes
    }
    stages {
        stage('Checkout') {
            steps {
                checkout scm
            }
        }
        stage('Build') {
            when {
                expression { return env.GIT_TAG != null }
            }
            steps {
                echo "Building for tag: ${env.GIT_TAG}"
                // Add build steps here
            }
        }
        stage('Deploy') {
            when {
                expression { return env.GIT_TAG != null }
            }
            steps {
                echo "Deploying for tag: ${env.GIT_TAG}"
                // Add deployment steps here
            }
        }
    }
}

Configure the Jenkins Job: We can create a new pipeline job in Jenkins. Or we can change an existing one to use our Jenkinsfile.
Set Up GitHub/GitLab Webhook: We need to make sure our GitHub or GitLab repository has a webhook. This webhook will trigger the Jenkins build when we create a tag. We can usually find this in the repository settings under “Webhooks”. For GitHub, we can use these settings:
- Payload URL: http://<JENKINS_URL>/github-webhook/
- Content type: application/json
- For events to trigger this webhook, select Let me select individual events. and check Release.
Environment Variables: We have to make sure our Jenkins job sets the GIT_TAG variable when a new tag is found. Jenkins does this automatically when we use the Git plugin.
Test the Pipeline: We can create a new tag in our Git repository and push it. Then, we should check Jenkins to see if the pipeline runs and the stages work well.

For more info on triggering Jenkins builds from Git events, we can look at this resource.

This setup helps us use Jenkins Pipeline for tag detection and makes our CI/CD workflow smoother.

Frequently Asked Questions

1. How can we trigger a Jenkins build when we create a new tag in GitHub?

To trigger a Jenkins build when we create a new tag in GitHub, we can set up a webhook. This webhook sends tag events to our Jenkins server. With this setup, Jenkins listens for tag creation and starts the build process by itself. For a simple guide, check our article on how to trigger Jenkins builds.

2. What permissions does Jenkins need to access GitHub tags?

Jenkins needs the right permissions to access our GitHub repository and its tags. We must make sure that the Jenkins integration has the right access, usually with a GitHub personal access token. For more details about setting permissions, look at our article on how to set up Jenkins CI.

3. Can we use Jenkins Pipeline to automate tag detection?

Yes, we can use Jenkins Pipeline to automate the detection of new tags in our Git repository. We can create a pipeline that triggers on tag events. This gives us more flexibility and control over our build process. For more information about using Jenkins pipeline for different tasks, visit our guide on fixing Jenkins pipeline issues.

4. Is it possible to set up Jenkins to check for new tags instead of using webhooks?

Yes, we can set up Jenkins to check our Git repository for new tags regularly. This way can work as a backup if the webhook setup is not very reliable. For more steps on tagging and checking setups, see our article on how to configure Git post-commit hooks.

5. How do we fix it if Jenkins does not trigger on tag events?

If Jenkins does not trigger builds on tag events, we should first check our webhook setup in GitHub for mistakes. We also need to make sure that Jenkins has the right plugins installed and is set up correctly to listen for tag events. For tips on troubleshooting, see our post about fixing common Jenkins issues.

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