Trunk-based development refers to a version control management model where every developer divides their work into small short-lived code branches and then merges them into a core "trunk." This is a common practice among software developers and is done to streamline the merging and integration stages of the development process. The practice helps achieve continuous integration and continuous delivery and results in high performance in technology organizations. As the complexity of the codebase and the size of the team grows, trunk-based development helps keep the production releases flowing.
Advantages of Trunk-Based Development Model
Trunk-based development is an essential practice for continuous integration. If the building and testing processes are automated but the developers are working on lengthy, isolated feature branches that are only erratically integrated into a shared branch, then continuous integration cannot happen in the best way. Trunk-based development can help with that.
Once a developer finishes a short-term new work, he must merge the code into the main branch. However, they should not merge the changes into the main branch until it is confirmed that they can build successfully. During this phase, increasingly complex conflicts can arise, particularly if the codebase and teams are growing. These conflicts can occur when developers create separate branches that diverge from the main branch while other developers are merging overlapping codes at the same time. Fortunately, the trunk-based development model can reduce such conflicts.
Here are some benefits of the model:
Creates Short-lived Branches
Short-lived branches are a major benefit of the trunk-based model. In a feature flow, there are no branches that are truly short-lived and it can have multiple touchpoints where the branch required a pull request into yet another branch.
On the other hand, in the trunk-based development model, there is a single touchpoint for the branch with only a single pull request. By reducing the number of pull requests as the new code flows through the system, you can minimize friction in the process and eliminate any bottlenecks between writing the code and delivering it to the customer.
Enables Continuous Code Integration
In the trunk-based development model, a steady stream of codebase flows into the main branch. This enables continuous integration. When the new branch is merged into the trunk, code coverage tests and automated integration are run to ensure the quality of the code.
Ensures Continuous Code Review
Since the trunk-based development model allows short-term codes to merge with the trunk, it makes for a more efficient code reviewing process. Small branches allow developers to quickly review any small changes. This makes it much easier as compared to reviewing long-lived feature branches where the developer has to read multiple pages of coding and manually inspect a sprawling surface of code changes.
Allowing Quicker Releases
The trunk-based development model allows DevOps teams to send new changes to production rapidly. Research shows that shortening the time period between writing codes and shipping results in many benefits, like the opportunity to build more features that customers like and delivering fewer bugs.
On the other hand, teams that use the feature-branch development model often have slow and long deployment cycles.
Best Practices of Trunk-Based Development Model
Trunk-based development allows DevOps teams to make code releases quickly, consistently, and efficiently. Here are a few best practices to make the most out of this model.
Develop in Small Batches
By making small changes that translate to a few lines of code changes can prevent developers from becoming overwhelmed. It is easier for DevOps teams to have meaningful conversations and make quick, more informed decisions when they are reviewing only a small area of code rather than a large set of code changes.
Feature flags allow the DevOps team to wrap new code changes into an inactive code path to be activated at a later time. This eliminates the need to create another repository feature branch and allows the new feature code to commit directly to the core branch within the path of a feature flag.
Implement Automated Testing
A meaningful and comprehensive suite of automated unit tests that are run before every commit review code issues and automatically approves or rejects them. This helps the DevOps team create commits more accurately and at a faster rate by running them through the tests and checking for new issues.
Retain Few Active Branches in the Repository
Once a branch merges with the core trunk, it is good practice to delete it. The application’s code repository that has a large number of active code branches may become vulnerable to negative side effects. Even though it may be convenient for developers to see what work is in progress by looking at the active branches, it can become unwieldy and cumbersome to work and renders any benefit useless if there are too many stale branches hanging around.
Merge Branches to the Trunk At Least Once a Day
High-performing DevOps teams should close and merge any ready branches at least once every day and ideally multiple times every day. This practice helps keep the rhythm and sets a pace for tracking releases. The team can then tag the trunk as a release commit once the day ends, which can offer benefits like creating an agile release increment every day.
Lower Number of Code Freezes
Trunk-based development allows DevOps teams to forego planned code freezes or integration phase pauses. The model allows updates to flow continuously. Developers should try to avoid blocking code freezes and strive to ensure the release pipeline is not slowed down.
Nowadays, trunk-based development is the highest standard for high-performing DevOps teams since it can start and maintain a software release cadence with the use of a simplified Git branching strategy. This model offers developers more control and flexibility over how the software is delivered to the end-user.
As you explore the trunk-based development model, keep in mind that one of the key principles of this model is continuous improvement. Hence, you should avoid jumping the gun and instead try to get better at a steady rate each day.