JenkinsHow-ToBeginner · 4 min read

How to Integrate GitLab with Jenkins for CI/CD

To integrate GitLab with Jenkins, install the GitLab plugin in Jenkins, create a Jenkins job linked to your GitLab repository, and configure a webhook in GitLab to trigger Jenkins builds on code changes. This setup automates your CI/CD pipeline by connecting GitLab commits to Jenkins jobs.

📐

Syntax

The integration involves these key parts:

GitLab Plugin: Jenkins plugin to connect with GitLab.
Jenkins Job: A pipeline or freestyle job configured to pull code from GitLab.
GitLab Webhook: URL in GitLab that triggers Jenkins on push or merge events.

Each part works together to automate builds when code changes.

yaml

gitlab:
  webhook_url: http://<jenkins-server>/project/<job-name>

jenkins:
  plugins:
    - gitlab
  job:
    scm: git
    repository_url: https://gitlab.com/your-repo.git
    triggers:
      - gitlab webhook

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Example

This example shows how to create a Jenkins pipeline job triggered by GitLab webhook:

groovy

pipeline {
  agent any
  triggers {
    GenericTrigger(
      genericVariables: [
        [key: 'ref', value: '$.ref']
      ],
      causeString: 'Triggered by GitLab push',
      token: 'your-webhook-token',
      printContributedVariables: true,
      printPostContent: true,
      regexpFilterText: '$.ref',
      regexpFilterExpression: 'refs/heads/main'
    )
  }
  stages {
    stage('Checkout') {
      steps {
        git url: 'https://gitlab.com/your-repo.git', branch: 'main'
      }
    }
    stage('Build') {
      steps {
        echo 'Building the project...'
      }
    }
  }
}

Output

[Pipeline] Start of Pipeline [Pipeline] node Running on Jenkins in /var/lib/jenkins/workspace/your-job [Pipeline] { [Pipeline] stage [Pipeline] { (Checkout) [Pipeline] git Cloning repository https://gitlab.com/your-repo.git [Pipeline] } [Pipeline] stage [Pipeline] { (Build) [Pipeline] echo Building the project... [Pipeline] } [Pipeline] } [Pipeline] // node [Pipeline] End of Pipeline

⚠️

Common Pitfalls

Missing or incorrect webhook URL: Ensure the webhook URL in GitLab matches Jenkins job URL exactly.
Webhook token mismatch: The token set in Jenkins GenericTrigger must match the one in GitLab webhook settings.
Insufficient Jenkins permissions: Jenkins user must have access to the GitLab repository.
Firewall or network issues: GitLab must be able to reach Jenkins server URL.

text

Wrong webhook URL example:
https://jenkins-server/wrong-path

Correct webhook URL example:
https://jenkins-server/project/your-job

Wrong token in Jenkins:
GenericTrigger(token: 'wrong-token')

Correct token in Jenkins:
GenericTrigger(token: 'your-webhook-token')

📊

Quick Reference

Summary tips for GitLab and Jenkins integration:

Install and configure GitLab plugin in Jenkins.
Create Jenkins job with Git SCM pointing to GitLab repo.
Set up GitLab webhook to Jenkins job URL with correct token.
Test webhook delivery from GitLab to Jenkins.
Check Jenkins logs for webhook trigger confirmation.

✅

Key Takeaways

Install the GitLab plugin in Jenkins to enable integration features.

Configure a Jenkins job to pull code from your GitLab repository.

Set up a GitLab webhook pointing to Jenkins job URL to trigger builds automatically.

Ensure webhook tokens and URLs match exactly to avoid trigger failures.

Test the webhook connection and monitor Jenkins logs for successful triggers.