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How Feature Flags Enable Trunk-Based Development


Software development holds a central role in business success in today’s world. However, the game has progressed from merely creating new features quickly and reliably. The true test lies in producing features that significantly affect customers’ lives and propel business growth – a concept known as Impact-Driven Development.

Engineering teams relentlessly strive to innovate and make a difference. Yet, the challenge is to accomplish this without losing sight of the end goal – delivering genuine value over simply producing features. Two potent tools at their disposal are trunk-based development and feature flags.

Trunk-based development is a software development approach that advocates frequent integration, reducing the risk of conflicts. Maintaining a clean, updated codebase drastically enhances the efficiency and speed of the development process.

Trunk-based development can’t be accomplished without a way to commit unfinished code to a build that may end up in production. That’s where feature flags come in. With feature flags, developers gain control over the visibility and behavior of features in their applications. The possibility of testing new features in a live environment without jeopardizing the application’s stability is thus realized.

What Is Trunk-Based Development

Trunk-based development is a software development method where all developers work on one shared codebase, referred to as the ‘trunk’. Rather than creating separate branches for each feature, developers integrate their work into the main codebase, sometimes multiple times a day.

Reducing risk is the main goal with trunk-based development. Like practicing together in an orchestra to avoid a performance catastrophe, frequent code integration diminishes the chances of severe conflicts or bugs emerging when merging different code branches later. It also supports continuous integration and continuous delivery (CI/CD), essential components of modern software development. Trunk-based development forms the foundation for these practices.

Advantages of Trunk-Based Development

Adopting trunk-based development offers several benefits:

  • Quicker release cycles: Regular integration on the same codebase allows for more rapid and frequent software releases, eliminating the need to wait for completion and merging of long-lived branches.
  • Enhanced team collaboration: Working on the same codebase naturally promotes communication and collaboration. Developers can easily comprehend the changes their colleagues are making.
  • Lowered risk: Frequent integration allows for early detection and resolution of conflicts or bugs, reducing the danger of dealing with multiple conflicting changes at once.
  • Better code quality: Regular integrations and code reviews continuously refine and improve the codebase, often leading to superior code quality.

Shifting to trunk-based development may require changes in mentality and development practices. However, once the transition is made, it can significantly enhance the speed, efficiency, and quality of your software development processes.

Introduction to Feature Flags

Feature flags, or feature toggles, are essential tools in a developer’s toolkit. They allow developers to switch specific functionality on and off for one user, any group of users, or the entire user population–all without altering the codebase.

Understanding Feature Flags

A feature flag is essentially made of a conditional statement in a software application, enabling or disabling a specific feature based on a predetermined condition. These conditions could vary from the type of user, the time of day, or any other criteria set by the developer. If the condition is met, the feature is activated. If not, it remains inactive. This flexibility allows developers to add new features to an application and control their availability to users.

While feature flags are not new, their importance and usage have grown with the rise of agile development and continuous integration/continuous delivery (CI/CD) practices.

The Benefits of Using Feature Flags

Feature flags offer various advantages, making them a versatile tool for software developers. Let’s delve into some of the key benefits:

  • Greater control: Feature flags provide developers with absolute control over when and to whom a feature becomes available. They can test new features with a select group of users before a full-scale deployment (i.e. a “canary release”), ensuring safer releases and minimizing the risk of a faulty feature affecting all users.
  • Improved testing capabilities: Developers can test features directly in the production environment using feature flags. This allows for practical testing scenarios and the ability to rectify issues before the feature is fully live.
  • Risk reduction: Feature flags facilitate “dark launching,” which involves releasing features to production, but not visible to users or impacting their experience in any way. The very first dark launch may have been Facebook’s test of a chat app that used real user traffic to test essential functionality without exposing any of it in the UI. This approach substantially reduces the risk of introducing bugs into the live application.
  • Facilitating experimentation: Feature flags aid A/B testing enabling developers to experiment with different variations of a feature to evaluate their performance. The results of these experiments can inform data-driven decisions about future feature launches.
  • Efficient rollback: If a released feature causes problems or underperforms, feature flags allow for easy rollbacks. Developers can simply deactivate the feature rather than redeploying the application without it.

Collectively, these advantages make feature flags invaluable in modern software development. They allow developers to innovate more rapidly, minimize risks, and deliver more value to users. 

So how do feature flags enable trunk-based development? Let’s dig in.

Combining Feature Flags With Trunk-Based Development

Using trunk-based development principles and feature flags together can greatly enhance your software development process. This combination improves code integration and team collaboration.

Improving Code Integration and Testing

Feature flags boost code integration and testing capabilities in trunk-based development. Developers working directly on the trunk can commit not-yet-finished code to the trunk turned “off” to maintain safety while avoiding the difficulties of managing separate branches. They can use a feature flag to control the exposure of a new feature in the live environment.

Rather than waiting to merge a completed feature into the trunk, developers can continuously integrate their work. As they create a feature, they can test it in real-time using feature flags, even if the feature is not yet ready for release. This approach allows them to detect bugs and conflicts early on.

Feature flags also enable testing features directly in the production environment. This results in more accurate testing scenarios and helps uncover issues that might not show up in a staging environment.

Boosting Team Collaboration and Feedback

Feature flags facilitate better team collaboration in trunk-based development. Multiple teams can work on different features of the same codebase simultaneously without disruption. Each team uses a feature flag to control their feature’s visibility and behavior, contributing to the same codebase independently.

  • Real-time feedback: Feature flags allow developers to share their work with other teams or stakeholders and receive immediate feedback, enhancing the development process.
  • Greater transparency: Working on the same codebase provides visibility into what others are doing, promoting unity and helping identify potential conflicts or dependencies between features.
  • Improved efficiency: Feature flags enable independent development and testing of different features, increasing productivity and reducing the risk of bottlenecks.

Integrating feature flags into trunk-based development streamlines the software development process. It improves code integration, promotes smoother team collaboration, and reduces the risk of bugs and conflicts. However, managing feature flags diligently is crucial to prevent them from becoming technical debt.

A New Shift in Software Development

We’re progressing into a future of software development that values speed, collaboration, and more effective risk management.The shift significantly depends on the blending of trunk-based development and feature flags.

Feature flags give control and flexibility to developers, promoting innovation. By enabling safer releases and practical testing scenarios, they reduce risk and provide an enhanced user experience.

In contrast, trunk-based development speeds up release cycles and encourages team collaboration by offering a shared codebase. This strategy ensures frequent integration, which in turn diminishes risks and improves the overall code quality.

Used together, these two tools usher in Impact-Driven Development. This approach enables engineering teams to prioritize delivering value over merely producing features. In effect, the combination of feature flags and trunk-based development transforms software development processes, making them more efficient, reliable, and impactful. 

To learn more about how feature flags can make your trunk-based development even more impactful, schedule a demo of Split.  Split helps developers and development teams ship more great code every day.

Switch It On With Split

The Split Feature Data Platform™ gives you the confidence to move fast without breaking things. Set up feature flags and safely deploy to production, controlling who sees which features and when. Connect every flag to contextual data, so you can know if your features are making things better or worse and act without hesitation. Effortlessly conduct feature experiments like A/B tests without slowing down. Whether you’re looking to increase your releases, to decrease your MTTR, or to ignite your dev team without burning them out–Split is both a feature management platform and partnership to revolutionize the way the work gets done.  Schedule a demo to learn more.

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