Jenkins to GitLab: The ultimate guide to modernizing your CI/CD environment

In today's dynamic landscape of software development, certain requirements have become paramount for delivering high-quality software rapidly. These requirements include the need for cloud compatibility, faster development cycles, improved collaboration, containerization, enhanced development experiences, and the integration of AI-driven capabilities for better efficiency and speed. Jenkins, a longstanding and respected continuous integration (CI) tool, has admirably played a role in many teams' software development for years. However, as more teams adopt DevOps/DevSecOps strategies for their software delivery, leveraging the integrated CI that is available in a DevSecOps platform like GitLab can provide benefits that Jenkins does not.

Some organizations find themselves hesitating to migrate, not because they doubt the benefits of a top-tier CI/CD solution such as GitLab, but due to the complexities of their existing Jenkins implementations. It's understandable that such a transition can seem daunting.

In this blog, you'll find several migration strategies to help transition from Jenkins to GitLab and make the process smoother and more manageable.

Migrating to GitLab

It's become evident that for organizations seeking a CI/CD solution that can seamlessly support their evolving demands, GitLab emerges as a powerful game-changer. Let's explore why transitioning to this advanced platform is transformative for Jenkins users.

Why migrate to GitLab

Before we delve into the migration approaches, let's take a moment to understand GitLab CI and what makes it a compelling choice for modern CI/CD needs.

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GitLab CI overview

GitLab CI is an integral part of the GitLab AI-powered DevSecOps Platform, which offers a comprehensive and unified solution for DevSecOps and CI/CD. GitLab's design revolves around streamlining development workflows, fostering collaboration, enhancing security, and ensuring scalability.

Key features of GitLab CI

These are the key features of GitLab CI:

• Unified platform: GitLab CI is more than just a CI/CD tool; it's part of a broader ecosystem that includes source code management, project management, security features, analytics and more. This unified platform streamlines workflows and enhances collaboration among development teams.
• Containerization and orchestration: GitLab CI/CD is designed with containerization in mind, offering native support for Docker and Kubernetes. This enables seamless integration of container technologies into your CI/CD pipelines.
• Security by design: Security is a top priority, and GitLab CI incorporates features such as static code analysis and vulnerability scanning to help teams identify and address security issues early in the development process.
• GitOps principles: GitLab CI aligns with GitOps principles, emphasizing version-controlled, declarative configurations for infrastructure and application deployments. This approach enhances the reliability and repeatability of deployments.

Get familiar with GitLab CI with this tutorial:

With that understanding of GitLab CI's capabilities, let's explore the migration steps and strategies for Jenkins users looking to leverage the benefits of GitLab CI.

A recommended step-by-step Jenkins-to-GitLab CI migration

When considering a migration from Jenkins to GitLab CI, we strongly recommend following a well-structured, step-by-step approach to ensure a seamless transition. Here's our recommended process:

1. Pipeline assessment: Start by conducting a comprehensive inventory of all your existing pipelines in Jenkins. This initial step will help you gain a clear understanding of the scope and complexity of the migration.
2. Parallel migration: Begin the migration process by selecting individual pipelines and moving them to GitLab CI one at a time. Continue to maintain the use of Jenkins for your ongoing work during this transition to minimize disruptions.
3. Code verification: We advise beginning with verification checks in CI. Run both the Jenkins and GitLab CI pipelines in parallel. This dual approach allows you to directly compare the two workflows and identify any issues in the new GitLab workflows. During this phase, keep the GitLab workflow as an optional choice while Jenkins remains required.
4. Continuous validation: After running both pipelines in parallel for a full iteration, thoroughly evaluate the outcomes from each pipeline. This evaluation should consider various factors, including status codes, logs, and performance.
5. GitLab CI transition: As you gain confidence in the reliability and effectiveness of GitLab CI through the parallel runs, make the transition to the GitLab CI workflow as the required standard while Jenkins continues to operate in the background.
6. Jenkins phaseout: After a second iteration, when you are confident in the performance and stability of GitLab CI, you can begin to remove the Jenkins job from your code verification pipeline. This successful transition will enable you to retire Jenkins from this particular aspect of your CI/CD process.

This recommended approach ensures that your migration is a gradual evolution, allowing you to identify and address any issues or discrepancies before fully committing to GitLab CI. Running Jenkins and GitLab CI pipelines in parallel provides valuable insights and ensures the effective streamlining of your CI/CD processes.

Preparing for migration: Training and communication

To ensure a smooth and successful migration from Jenkins to GitLab CI, follow these essential steps:

• Stakeholder communication: Start by announcing your migration plans and timelines to all relevant stakeholders. This includes DevOps teams, developers, and QA engineers. Transparency in communication is crucial to ensure that everyone understands the objectives and expectations of the migration.
• Knowledge-level training: Conduct knowledge-level training sessions for your teams to promote GitLab CI adoption. Cover topics such as using GitLab CI, understanding the YAML syntax, and how to create a basic pipeline. Provide team members with the knowledge and skills necessary to navigate the new GitLab CI environment effectively.
• Hands-on learning: Encourage hands-on learning by pairing up developers. Create opportunities for them to learn from each other's experiences throughout the migration process.

By following these instructions for training and communication, you'll build a strong foundation for a successful migration, empowering your teams to adapt and thrive in the new environment.

3 Jenkins-to-GitLab CI migration strategies

There are different strategies to consider. These three strategies offer flexibility, allowing organizations to choose the path that best aligns with their specific needs and resources. Let's explore these strategies in detail to help you make an informed decision about which one suits your organization best.

Migration Strategy 1: Using GitLab CI for new projects

The first migration strategy involves a gradual transition. While you maintain your existing Jenkins infrastructure for ongoing projects, you introduce GitLab CI for new projects. This approach allows you to harness the modern features of GitLab CI without disrupting your current work.

Benefits of Migration Strategy 1

The benefits of this approach include the following:

• New projects can leverage GitLab CI's advanced features right from the start.
• This strategy minimizes the risk of disrupting existing workflows, as your existing Jenkins setup remains intact.
• Your team can gradually adapt to GitLab CI, building confidence and expertise without the pressure of an immediate full-scale migration.

Challenges of Migration Strategy 1

The challenges of this approach include the following:

• Operating two CI/CD platforms simultaneously can introduce complexity, especially in terms of integration and team collaboration.
• Managing projects on different platforms may require careful coordination to ensure consistency in processes and security practices.

This strategy offers a smooth and manageable transition by allowing you to harness GitLab CI's strengths for new projects, while your existing Jenkins infrastructure continues to support ongoing work.

Migration Strategy 2: Migrating only strategic projects

In this strategy, you identify specific projects within your organization that stand to benefit the most from the capabilities of GitLab CI. Instead of preparing for a wholesale migration, you start by focusing your efforts on migrating these strategically selected projects first.

Benefits of Migration Strategy 2

The benefits of this approach include the following:

• By concentrating on key projects, you can realize significant improvements in those areas where GitLab CI aligns with specific needs.
• This approach reduces the complexity of migrating everything at once, minimizing the potential for disruptions.
• You can gradually build confidence with GitLab CI and its benefits before considering further migrations.

Challenges of Migration Strategy 2

The challenges of this approach include the following:

• Even though you're not migrating all projects, the chosen projects' migration can still be intricate and require careful planning.
• Ensuring seamless collaboration between projects on different platforms may require additional attention.

This strategy allows you to maximize the impact of GitLab CI by focusing on strategic areas, minimizing risk, and gradually gaining experience with the new tool.

Migration Strategy 3: Migrating everything

The third strategy is a comprehensive migration where you commit to moving all your CI/CD processes, projects, and workflows to GitLab CI. This approach aims for uniformity and simplification of CI/CD across all projects. This strategy can benefit from taking an iterative approach. Consider starting with new projects, followed by migrating strategic projects, and then leverage your growing knowledge and experience with GitLab CI to complete the migration of remaining projects.

Benefits of Migration Strategy 3

The benefits of this approach include the following:

• Uniform CI/CD processes across all projects can streamline administration and maintenance, reducing complexity.
• You can take full advantage of GitLab CI's modern capabilities, from Infrastructure as Code to enhanced security features.
• As your projects grow, GitLab CI is designed to handle increased demands, ensuring long-term scalability.

Challenges of Migration Strategy 3

The challenges of this approach include the following:

• A full-scale migration can be intricate, requiring meticulous planning and implementation.
• The transition may disrupt ongoing projects and require a significant time investment.
• Investment in training and potential tool migration expenses should be considered.

Opt for this approach if uniformity and consolidation of CI/CD processes are a high priority, and you have the resources to execute a full migration.

The migration strategy you select should align with your organization's specific needs and circumstances. In all cases, the ultimate goal is to enhance your development process with modern CI/CD tools like GitLab CI, which offers scalability, infrastructure automation, security, and collaboration features that align with today's development needs.

Technical insights: How the migration works

Moving your CI/CD workflows from Jenkins to GitLab CI is a transformative journey, and understanding how it works is vital for a successful transition.

Understanding the configurations: Jenkinsfile vs. .gitlab-ci.yml

The heart of your CI/CD pipeline lies in the configurations defined in your Jenkinsfile (for Jenkins) and .gitlab-ci.yml (for GitLab CI). While there are some similarities between these configuration files, there are notable differences as well.

Similarities

• Both files define the stages, jobs, and steps of your CI/CD process.
• You specify the desired build, test, and deployment steps in both files.
• Environment variables and settings can be configured in either file.

Differences

• Jenkinsfile uses Groovy for scripting, while .gitlab-ci.yml uses YAML. This change in language affects the way you write and structure your configurations.
• The process of defining pipelines is more intuitive in .gitlab-ci.yml, with a cleaner, more human-readable syntax.
• GitLab CI provides a wide range of built-in templates and predefined jobs, simplifying configuration and reducing the need for custom scripting.

Manually converting the pipeline configuration

Currently, migrating your existing Jenkins pipelines to GitLab CI is typically done manually. This means analyzing your Jenkinsfile and re-creating the equivalent configurations in .gitlab-ci.yml. While there are similarities in the concepts and structure, the differences in syntax and the specific capabilities of each platform require careful consideration during the migration.

Strategic planning for a smooth transition

Migrating from Jenkins to GitLab CI requires meticulous planning to ensure a seamless transition. It's crucial to assess the disparities between the two systems and evaluate their impact on your workflow, considering aspects like security, cost, time, and capacity.

Once you've identified these differences and devised your migration strategy, break down the migration into key steps. These include setting up GitLab CI pipelines, securely transferring data from Jenkins to GitLab CI, and integrating GitLab CI into your existing tools and processes.

Case study: A seamless transition for Lockheed Martin

Let's look at a real-world case study to illustrate the effectiveness of the "Migrate Everything" strategy. Lockheed Martin, the world’s largest defense contractor, had been using Jenkins for several years. As their project portfolio expanded, they realized that their Jenkins implementation with a wide variety of DevOps tools was becoming increasingly complex to manage. They were also eager to adopt modern CI/CD capabilities that Jenkins struggled to provide.

In collaboration with GitLab, Lockheed Martin decided to undertake a comprehensive migration to GitLab CI. Their goals included achieving consistency in their CI/CD processes, simplifying administration and maintenance, and taking full advantage of The GitLab Platform’s robust features.

The comprehensive migration strategy proved to be a resounding success for Lockheed Martin. With GitLab CI, they not only streamlined their CI/CD processes but achieved remarkable results. They managed to run CI pipeline builds a staggering 80 times faster, retired thousands of Jenkins servers, and reduced the time spent on system maintenance by a staggering 90%. This monumental shift resulted in a significant increase in efficiency and productivity for Lockheed Martin.

This case study showcases how a comprehensive migration strategy can be effective for organizations looking to leverage GitLab capabilities across all their projects.

For more in-depth insights into Lockheed Martin's successful transition to GitLab and how it streamlined their software development processes, check out the detailed case study.

GitLab documentation and support

For those embarking on this migration journey, GitLab offers documentation to guide you through the process. You can find valuable resources in GitLab's official documentation.

In addition to documentation, GitLab's Professional Services team is available to assist organizations in their migrations. They bring expertise and experience to ensure a smooth transition. Whether it's understanding the nuances of Jenkinsfile to .gitlab-ci.yml conversion or optimizing your CI/CD workflows, their support can be invaluable.

Try GitLab CI/CD today with a free trial of Ultimate.