Jenkins (FREE ALL)

Moved to GitLab Free in 13.7.

You can trigger a build in Jenkins when you push code to your repository or create a merge request in GitLab. The Jenkins pipeline status displays on merge requests widgets and on the GitLab project's home page.

For an overview of the Jenkins integration for GitLab, see GitLab workflow with Jira issues and Jenkins pipelines.

Use the Jenkins integration when:

You plan to migrate your CI from Jenkins to GitLab CI/CD in the future, but need an interim solution.
You're invested in Jenkins plugins and choose to keep using Jenkins to build your apps.

NOTE: This documentation focuses only on how to configure a Jenkins integration with GitLab. Learn how to set up Jenkins on your local machine in the developer documentation, and how to migrate from Jenkins to GitLab CI/CD in the Migrating from Jenkins documentation.

The Jenkins integration requires configuration in both GitLab and Jenkins.

Grant Jenkins access to the GitLab project

To grant Jenkins access to the GitLab project:

Create a personal, project, or group access token.
- Create a personal access token to use the token for all Jenkins integrations of that user.
- Create a project access token to use the token at the project level only. For instance, you can revoke the token in a project without affecting Jenkins integrations in other projects.
- Create a group access token to use the token for all Jenkins integrations in all projects of that group.
Set the access token scope to API.
Copy the access token value to configure the Jenkins server.

Configure the Jenkins server

Install and configure the Jenkins plugin. The plugin must be installed and configured to authorize the connection to GitLab.

On the Jenkins server, select Manage Jenkins > Manage Plugins.
Install the Jenkins GitLab Plugin.
Select Manage Jenkins > Configure System.
In the GitLab section, select Enable authentication for '/project' end-point.
Select Add, then choose Jenkins Credential Provider.
Select GitLab API token as the token type.
In API Token, paste the value you copied from GitLab and select Add.
Enter the GitLab server's URL in GitLab host URL.
To test the connection, select Test Connection.

For more information, see Jenkins-to-GitLab authentication.

Configure the Jenkins project

Set up the Jenkins project you intend to run your build on.

On your Jenkins instance, go to New Item.
Enter the project's name.
Select Freestyle or Pipeline and select OK. We recommend a Freestyle project, because the Jenkins plugin updates the build status on GitLab. In a Pipeline project, you must configure a script to update the status on GitLab.
Choose your GitLab connection from the dropdown list.
Select Build when a change is pushed to GitLab.
Select the following checkboxes:
- Accepted Merge Request Events
- Closed Merge Request Events
Specify how the build status is reported to GitLab:
- If you created a Freestyle project, in the Post-build Actions section, choose Publish build status to GitLab.
- If you created a Pipeline project, you must use a Jenkins Pipeline script to update the status on GitLab.
  
  Example Jenkins Pipeline script:
```
pipeline {
   agent any

   stages {
      stage('gitlab') {
         steps {
            echo 'Notify GitLab'
            updateGitlabCommitStatus name: 'build', state: 'pending'
            updateGitlabCommitStatus name: 'build', state: 'success'
         }
      }
   }
}
```
  For more Jenkins Pipeline script examples, go to the Jenkins GitLab plugin repository on GitHub.

Configure the GitLab project

Configure the GitLab integration with Jenkins in one of the following ways.

Configure a Jenkins integration (recommended)

GitLab recommends this approach for Jenkins integrations because it is easier to configure than the webhook integration.

On the left sidebar, at the top, select Search GitLab ({search}) to find your project.
Select Settings > Integrations.
Select Jenkins.
Select the Active checkbox.
Select the events you want GitLab to trigger a Jenkins build for:
- Push
- Merge request
- Tag push
Enter the Jenkins server URL.
Optional. Clear the Enable SSL verification checkbox to disable SSL verification.
Enter the Project name.

The project name should be URL-friendly, where spaces are replaced with underscores. To ensure the project name is valid, copy it from your browser's address bar while viewing the Jenkins project.
If your Jenkins server requires authentication, enter the Username and Password.
Optional. Select Test settings.
Select Save changes.

Configure a webhook

If you are unable to provide GitLab with your Jenkins server login, you can use this option to integrate GitLab and Jenkins.

In the configuration of your Jenkins job, in the GitLab configuration section, select Advanced.
Under Secret Token, select Generate.
Copy the token, and save the job configuration.
In GitLab, create a webhook for your project, enter the trigger URL (such as https://JENKINS_URL/project/YOUR_JOB) and paste the token in Secret Token.
To test the webhook, select Test.

Troubleshooting

Error during GitLab configuration - "Connection failed. Please check your settings"

If you get this error message while configuring GitLab, the following are possible causes:

GitLab is unable to reach your Jenkins instance at the address. If your GitLab instance is self-managed, try pinging the Jenkins instance at the domain provided on the GitLab instance.
The Jenkins instance is at a local address and is not included in the GitLab installation's allowlist.
The credentials for the Jenkins instance do not have sufficient access or are invalid.
The Enable authentication for /project end-point checkbox is not selected in your Jenkins plugin configuration.

Error in merge requests - "Could not connect to the CI server"

You might get the Could not connect to the CI server error if GitLab did not receive a build status update from Jenkins via the Commit Status API.

This issue occurs when Jenkins is not properly configured or there is an error reporting the status via the API.

To fix this issue, ensure you:

Configure the Jenkins server for GitLab API access.
Configure the Jenkins project, including the 'Publish build status to GitLab' post-build action.

Merge request event does not trigger a Jenkins pipeline

This issue can occur when the request exceeds the webhook timeout, which is set to 10 seconds by default.

For this issue, check:

Integration webhook logs for request failures.

/var/log/gitlab/gitlab-rails/production.log for messages like:

WebHook Error => Net::ReadTimeout

WebHook Error => execution expired

On self-managed GitLab instances, you can fix this issue by increasing the webhook timeout value.

Enable job logs in Jenkins

To troubleshoot an integration issue, you can enable job logs in Jenkins to get more details about your builds.

To enable job logs in Jenkins:

Go to Dashboard > Manage Jenkins > System Log.
Select Add new log recorder.
Enter a name for the log recorder.
On the next screen, select Add and enter com.dabsquared.gitlabjenkins.
Make sure that the Log Level is All and select Save.

To view your logs:

Run a build.
Go to Dashboard > Manage Jenkins > System Log.
Select your logger and check the logs.