Feature flags for stress-free continuous deployment

Feature flags (also known as feature toggles or switches) are conditional statements in code that determine whether a feature or functionality is visible and accessible to users of an application or service. They offer programmers a powerful tool for managing feature releases. Their capabilities are indispensable in software development, where agility and continuous, automated delivery are paramount.

Agility and automation form the basis of continuous deployment (CD), which aims to rapidly deliver new features, enhancements, and bug fixes to end users. Feature flags introduce an additional layer of control and risk mitigation into the CD pipeline. This piece will review the benefits of the CD approach and underscore how feature flags can keep your pipeline moving.

Continuous deployment and its benefits

CD benefits development teams and the software delivery lifecycle in several ways:

• Rapid and frequent release cycles: CD enables the regular and timely release of software updates and new features, allowing your teams to deliver value to users and quickly respond to market demands.
• Reduced risk and improved quality: The foundation of CD is automated testing, including unit, integration, and end-to-end tests. By automating testing and implementing continuous integration practices, teams can catch issues early in development.
• Faster time to recovery and improved resilience: CD emphasizes robust and automated deployment practices. Properly integrated automation and version control mechanisms mean you can roll changes back or forward in case of failures or production issues.

Let’s look at some of the ways feature flags can help facilitate these capabilities.

Feature flag strategies for continuous deployment

Feature flags are primarily used to separate feature releases from code deployments. Incorporating feature flags into the codebase lets you selectively enable or disable features at runtime without needing an entire deployment.

Decoupling deploy and release processes can prove invaluable for risk mitigation and user satisfaction. While it may be necessary to redeploy you application when introducing bug fixes or security patches, doing so to test the functionality or user reception of a new feature introduces unnecessary risk.

Imagine an app for aviation enthusiasts that lets users research aircraft and view information about planes flying in their region. After an initial release, the development team creates a notification feature to alert users when their favorite planes are within a specified range.

The developers test the feature and redeploy the code, but the new notification option causes 10% of users’ apps to crash. In addition, some customers complain that the alerts are not timely enough to be helpful. Now, developers must scramble to release yet another version to fix the crashing.

If the development team had used feature flags, they could have avoided a lot of hassle. Let’s explore how as we examine various feature flag types.

Types of feature flags

There are numerous categories of feature flags, each with a unique purpose, but all facilitating a smoother CD pipeline.

Release flags

Release (on/off) flags are the simplest type of feature flag. They let you enable or disable an entire feature or functionality, a critical capability for ready-to-deploy features that require gradual rollouts or an immediate shutoff if issues arise.

The aviation app team could use a release flag to toggle the notification feature during rollout, initially enabling a small percentage of users to test its functionality and provide feedback. This flag would let the team switch off the alert at the first sign of trouble rather than spending time and effort to modify the codebase and release a full app update.

Operational flags

Operational (ops) flags control a system’s operational aspects. These flags allow developer teams to toggle diagnostic features, adjust logging levels, enable performance monitoring tools, and manage specific system behaviors. These capabilities allow teams to make on-the-fly adjustments without a new deployment.

Before releasing the aviation app, the development team could have implemented an ops flag that adjusts the logging level for monitoring live aircraft data. By increasing the amount of detailed information logged during debugging or troubleshooting, the team could gather more detailed data about the app’s behavior and more accurately identify any issues or bottlenecks impeding the delivery of timely notifications.

Experimental flags

Experimental flags help test and iterate upon new software features or functions. By including a flag that restricts a component to designated user groups or specific individuals, your team can test multiple versions of the same function to gauge user preference, understand potential areas for improvement, and redesign based on the insights you gather.

After a successful initial release, the aviation app team will likely want to test new variations or enhancements to the alert feature. They could create an experimental flag to try a different algorithm for determining the proximity range of aircraft. By enabling this flag for a subset of users, the team can collect data and user feedback to evaluate the effectiveness of the updated notification algorithm, as well as user satisfaction. Based on the results, they could decide whether to roll out the experimental change fully or iterate further.

Access control flags

Access control flags (also known as permission or entitlement flags) control access to specific features based on user roles and privileges. They ensure specific features are available only to authorized users or groups. Applications using subscription tiers and multiple user types can integrate access control flags to enable fine-grained access management and personalized experiences.

Once successful, the aviation app could offer subscription tiers that separate basic users and premium subscribers. Access control flags would let the team moderate access to specific features based on these roles.

For example, the premium version of the notification feature might allow subscribers to track a specific plane or use weather data to determine its visibility. An access control flag decides if a user can access this feature based on their subscription status, enabling the team to manage feature availability without changing the underlying codebase.

The dual benefits of feature flags: flexibility and control

Feature flags provide greater flexibility and control within the CD process. They offer fine-grained management of feature releases and visibility without requiring extensive code deployments or rollbacks, which clog the pipeline.

Moreover, they provide the same high degree of control over an application’s behavior and configuration. Development teams can toggle functionality, change default settings, or configure feature variations based on user preferences. These capabilities provide a safety net when issues or errors arise.

Empowering progressive releases with feature flags

Feature flags enable progressive releases in a CD pipeline, reducing risk and improving system stability. Controlled rollouts ensure a stable and reliable deployment process by gradually introducing features and toggling them using feature flags. These toggling capabilities similarly facilitate A/B testing and — should an issue arise — a rapid rollback of the associated feature without affecting the entire system.

A/B testing with feature flags

A/B testing compares two or more versions of a webpage, user interface, or feature to determine which performs better. Using feature flags in this process empowers development teams to make evidence-based decisions and continuously improve their software. Your team can create several feature versions, assign them to different user segments, and measure their impact on user behavior, performance, and other specified metrics.

As you learned previously, segmenting users and assigning different feature variations allows development teams to gather data on user interaction and analyze each variation’s performance.

Rapid rollbacks with feature flags

The use of feature flags in rapid rollbacks promotes continuous delivery of fixes and updates to the production environment. When development teams detect an issue or error, they can swiftly turn off the feature flag associated with the problematic feature, effectively rolling back to a known and stable configuration.

Once the problem is fixed, feature flags let you re-enable the feature seamlessly, ensuring that users can access the updated and improved version in the shortest possible time. By taking advantage of feature flags in rapid rollbacks, development teams can maintain a continuous flow of fixes and updates, enhancing the software’s responsiveness and reliability.

Implementing feature flags in your delivery practice

Incorporating feature flags into software development practices requires careful planning and implementation. Here are some best practices to consider:

• Define clear objectives: Clearly define the desired goals for using feature flags in your development process. Determine how feature flags will align with your overall development strategy.
• Implement feature flag governance: Establish governance guidelines and roles for feature flag management within your development team. Clearly define who has the authority to create, modify, and remove feature flags.
• Monitor and measure: Implement robust monitoring and measurement mechanisms to track the performance and impact of your feature flags. Monitor key metrics, user behavior, and feedback to evaluate the success of feature flag implementations.

Addressing the challenges of feature flags

While feature flags offer significant benefits, they can also introduce challenges that must be addressed. Here are some common challenges and suggestions to help you mitigate them.

• Flag proliferation and technical debt: Flags can accumulate over time and lead to increased complexity and technical debt. Establish a governance process for flag creation and removal. Regularly review and clean up unused or obsolete flags.
• Testing complexity: When you introduce a feature flag, it must be tested. Having several flag configurations can therefore increase testing complexity. Adopt a comprehensive testing strategy that covers various flag combinations. Prioritize testing for critical and high-impact flags and their interactions with other components.
• Security and access control: Feature flags can introduce potential vulnerabilities if not properly managed. Ensure that access control is in place to prevent unauthorized flag modifications.

Conclusion

Feature flags are critical for ensuring low-risk CD, providing development teams with the flexibility and control to release bug-free, stable software. Incorporating feature flags into your development practices lets your team confidently release features and changes with the lowest chance of encountering serious issues.

By embracing CD and using feature flags effectively, you can deliver value more quickly to your users. CircleCI’s automation platform can help you unlock the full potential of continuous deployment in your organization. To get the most out of your delivery pipeline, sign up for a free CircleCI account today.