Trunk-based development is a streamlined approach to software development where all developers integrate their changes into a single mainline, or "trunk," frequently. This method is crucial for improving the integration process, reducing merge conflicts, and maintaining a deployable codebase, ensuring that updates are rapid and reliable. Unlike other branching models, trunk-based development emphasizes continuous integration and short-lived branches, making it a favorite among modern development teams.

What is trunk-based development?

Trunk-based development is a source-control branching model where developers integrate frequent updates directly into the main branch, known as the "trunk", “master branch”, or "mainline." This approach emphasizes continuous integration, ensuring the new code base is always deployable and reducing integration challenges.

Unlike Gitflow and feature branches, which involve multiple long-lived branches, trunk-based development uses short-lived branches or direct commits to the trunk. This reduces the risk of merge conflicts and streamlines the development workflow by avoiding the complexity of managing multiple branches.

How trunk-based development works

In trunk-based development, developers either work directly on the trunk (mainline) or use short-lived branches for specific tasks. The key is to keep branches short-lived and merge them back into the trunk frequently. This ensures that the main codebase remains up-to-date and deployable at all times.

Frequent commits and integrations are crucial to this approach. Developers commit small changes regularly, which helps in identifying and resolving issues early. This practice minimizes the complexity of integrating large sets of changes and reduces the risk of merge conflicts.

Continuous integration and automated testing are integral to trunk-based development. Automated tests run with each commit to ensure that new changes do not break the existing codebase. Continuous integration tools automatically merge changes into the trunk, provided all tests pass, maintaining the integrity of the mainline.

Example workflow

A typical workflow in trunk-based development might start with a developer creating a short-lived branch to work on a new feature or bug fix. The developer makes small, frequent commits to this branch, regularly integrating changes and running automated tests. Once the work is complete and all tests pass, the branch is quickly merged back into the trunk. This process ensures that new features and fixes are continuously integrated and deployed.

Role of feature flags or feature toggles in trunk-based development

Feature flags play a significant role in trunk-based development by allowing features to be integrated into the trunk without being immediately exposed to users. This enables developers to deploy incomplete features safely, conducting real-time testing and gradual rollouts. Feature flags help manage the risk associated with new features and provide the flexibility to enable or disable functionality as needed.

By using feature flags, software engineer teams can adopt a more flexible and controlled approach to deploying new features, further enhancing the benefits of trunk-based development.

Benefits of using the trunk-based development process

Reduced merge conflicts and avoidance of "merge hell"

One of the primary benefits of trunk-based development is the significant reduction in merge conflicts. By integrating small, frequent updates directly into the trunk, developers avoid the complex and time-consuming process of reconciling divergent branches, commonly known as "merge hell." This streamlined approach ensures that code changes are continuously incorporated, minimizing the risk of integration issues.

Maintaining a deployable codebase at all times

This branching strategy emphasizes maintaining a codebase that is always in a deployable state. Continuous integration and frequent commits ensure that new features and bug fixes are incrementally added and tested, keeping the mainline stable and ready for deployment at any moment. This practice supports a more agile and responsive development cycle, allowing for quicker releases and more reliable software.

Enhanced code quality and faster feedback loops

With trunk-based development, code quality is enhanced through rapid feedback loops. Automated testing runs with every commit, immediately identifying any issues introduced by new changes. This continuous testing process ensures that problems are detected and addressed promptly, leading to higher overall code quality. Additionally, the frequent integration of changes allows developers to receive feedback on their work quickly, facilitating continuous improvement.

Improved collaboration among team members

Trunk-based development fosters better collaboration among team members by encouraging a more unified and cohesive workflow. With all developers working on a single mainline or using short-lived branches, communication and coordination are simplified. This approach reduces the chances of code divergence and helps maintain consistency across the project. It also encourages regular code reviews and collaborative problem-solving, enhancing team dynamics and productivity.

Benefits for DevOps practices and continuous delivery

Trunk-based development aligns seamlessly with DevOps practices and continuous delivery principles. By maintaining a stable and deployable codebase, development teams can automate their deployment pipelines more effectively. Continuous integration ensures that code is regularly tested and integrated, supporting a culture of continuous delivery where updates can be released quickly and reliably. This synergy with DevOps practices leads to faster development cycles, more efficient workflows, and higher-quality software.

Implementing trunk-based development

Transitioning to trunk-based development from other branching models, such as Gitflow, involves several steps and the adoption of best practices to ensure a smooth and effective implementation.

Steps to transition from other branching models

1. Evaluate current workflow: Assess your current development process, identify pain points, and determine how trunk-based development can address these issues.

2. Plan the transition: Develop a clear plan for transitioning to trunk-based development, including timelines, key milestones, and responsibilities.

3. Training and onboarding: Provide training for your team on trunk-based development principles and practices. Ensure everyone understands the new workflow and tools.

4. Gradual implementation: Start by implementing trunk-based development on a smaller project or a subset of your codebase to allow your team to adapt gradually.

5. Refine and scale: Collect feedback, make necessary adjustments, and gradually scale the approach across all projects.

Best practices for successful implementation

1. Keeping branches short-lived:

Aim to keep branches short-lived to reduce the risk of integration issues. Regularly merge changes back into the trunk to maintain a consistent codebase.

1. Emphasizing code reviews and pull requests:

Implement a robust code review process. Use pull requests to ensure that all changes are reviewed by multiple team members before being integrated into the trunk.

1. Utilizing automated testing and continuous integration:

Set up automated tests that run with every commit to catch issues early. Use continuous integration tools to automatically merge changes into the trunk when tests pass.

Tools and strategies to support trunk-based development

1. Version control systems (VCS) like Git and GitHub:

Use VCS like Git to manage your codebase. GitHub can facilitate collaboration with features like pull requests, code reviews, and branch management.

1. Continuous integration tools:

Tools such as Jenkins, CircleCI, and Travis CI can automate the testing and integration process, ensuring that changes are continuously integrated into the trunk.

1. Feature management tools like Statsig:

Statsig provides feature management capabilities that support trunk-based development. Feature toggles allow for safe deployment of new features, enabling gradual rollouts and real-time testing.

Potential challenges in adopting trunk-based development

Adopting trunk-based development can present several challenges. One of the most significant hurdles is the initial resistance to change. Team members accustomed to traditional branching models like Gitflow might find it difficult to adjust to the more fluid and continuous nature of trunk-based development. This resistance can slow down the adoption process and create friction within the team.

Another challenge is ensuring team discipline in committing frequently. Trunk-based development relies heavily on small, incremental commits and regular integrations. Maintaining this discipline can be difficult, especially for teams used to working with longer-lived branches. Without consistent commitment practices, the benefits of trunk-based development, such as reduced merge conflicts and continuous integration, can be compromised.

Strategies to overcome these challenges

To overcome the initial resistance to change, it is crucial to invest in training and onboarding. Providing comprehensive training sessions that explain the benefits and principles of trunk-based development can help team members understand the value of this approach. Hands-on workshops and gradual onboarding processes can ease the transition, allowing team members to become comfortable with the new workflow at their own pace.

Establishing clear guidelines and best practices is another essential strategy. Clearly defined methodologies and guidelines on how to commit frequently, manage short-lived feature branches and long-lived feature branches, and conduct code reviews can help maintain discipline and consistency across the team. Best practices should be documented and regularly reviewed to ensure they are being followed and to make improvements as needed.

Trunk-based development use cases

Team size

Trunk-based development is particularly effective for large teams. With many developers working simultaneously, managing long-lived branches can become complex and error-prone. Trunk-based development mitigates these issues by encouraging frequent integration into the main codebase. This approach reduces the risk of integration conflicts and ensures that all team members are working with the most up-to-date version of the software. Large teams benefit from improved collaboration and streamlined communication, as everyone is working on a single branch.

Release frequency

For organizations that prioritize frequent releases, trunk-based development is an ideal methodology. By maintaining a continuously deployable codebase, teams can push updates to production more regularly and with greater confidence. This approach aligns well with DevOps practices, enabling continuous integration and continuous delivery (CI/CD). The ability to release small, incremental changes frequently allows teams to respond swiftly to market demands, user feedback, and bug fixes, thereby improving overall product quality and customer satisfaction.

Rapid prototyping and innovation

Trunk-based development is also well-suited for environments that emphasize rapid prototyping and innovation. The methodology's emphasis on short-lived branches and frequent commits allows teams to experiment with new features and ideas quickly. Feature flags can be used to deploy experimental features safely, enabling real-time testing and validation without disrupting the main codebase. This flexibility supports a culture of continuous improvement and innovation, helping teams to iterate quickly and effectively.

Complex, multi-team projects

In complex projects involving multiple teams, trunk-based development helps coordinate efforts and maintain consistency across the entire project. By integrating changes frequently into a single trunk, teams can avoid the pitfalls of divergent branches and "merge hell." This approach ensures that all teams are aligned and working towards the same goals, facilitating smoother integration and reducing the likelihood of conflicts. It also enables better visibility and tracking of progress, as all changes are continuously integrated and tested.

Legacy system modernization

When modernizing legacy systems, trunk-based development can provide a structured and efficient approach. Frequent commits and continuous integration allow teams to gradually refactor and improve the legacy codebase while keeping it operational. Short-lived branches enable developers to isolate specific areas of the system for updates, ensuring that changes are manageable and reversible if necessary. This incremental approach minimizes risks and disruptions, making it easier to transition from outdated technologies to modern architectures.

Trunk-based development keeps your code in the fast lane, ensuring rapid, reliable updates without the merge mayhem. With Statsig's feature management, you’re always on the right track, deploying new features safely and efficiently. The key takeaway? By integrating frequently and using tools like Statsig, you can maintain a deployable codebase, avoid 'merge mayhem,' and accelerate your development cycle. Trunk on, and watch your productivity soar!

Create a free account

You're invited to create a free Statsig account! Get started today with 2M free events. No credit card required, of course.

Create my account