Feature Flags

Feature Flags, also known as Feature Flags, are a software development technique that enables developers to turn on and off certain features or functionality of an application or service without deploying new code.

In essence, a feature toggle is a conditional statement that checks whether a particular feature is enabled or disabled, and determines the behavior of the application accordingly.

• 1. Category
• 1.1. Release Toggles
• 1.2. Experiment Toggles
• 1.3. Operations Toggles
• 1.4. Permission Toggles
• 1.5. Configuration Toggles
• 2. Principle
• 3. Best Practice
• 4. Terminology
• 5. References

1. Category

Feature flags can be implemented in a number of different ways, including using conditional statements in code, using configuration files, or using external services such as LaunchDarkly or Split. However, it's important to use feature flags judiciously, as they can add complexity to code and make it harder to maintain over time. It's also important to have a clear strategy for managing feature flags, including documenting them, testing them thoroughly, and removing them once they are no longer needed.

1.1. Release Toggles

Release toggles control whether a feature is released to users or not. They are typically used to control the rollout of new features and to perform canary releases.

• Early access toggle

  This toggle allows a small group of users to access a new feature before it's released to everyone else. It's often used to gather feedback and ensure that the feature works as intended before releasing it to a wider audience.

• Gradual release toggle

  This toggle enables a new feature to be gradually rolled out to a subset of users. This is useful for testing and monitoring the performance of the feature before releasing it to everyone.

• Rollback toggle

  This toggle is used to quickly disable a feature that has been released if it's causing issues or isn't working as intended. It can be a useful tool in ensuring that the application remains stable and reliable.

Example:

if (featureToggle.isEnabled("newFeature")) {
    // New feature code here
} else {
    // Old feature code here
}

1.2. Experiment Toggles

Experiment toggles control whether a feature is visible to users or not. They are typically used for A/B testing and other experimentation scenarios.

• A/B testing toggle

  This toggle allows developers to test different versions of a feature to see which one performs better. Users are randomly assigned to either the control group (which doesn't see the new feature) or the experimental group (which does see the new feature).

• Personalization toggle

  This toggle enables different versions of a feature to be shown to different users based on their demographics or behavior. This is useful for tailoring the user experience to different segments of the audience.

• Feature subset toggle

  This toggle enables a feature to be released in different stages or variations to different groups of users. For example, some users might see a simplified version of the feature while others see a more advanced version.

Example:

if (featureToggle.isEnabled("newFeature", userId)) {
    // New feature code here
} else {
    // Old feature code here
}

1.3. Operations Toggles

Operations toggles control the behavior of an application or service in different environments, such as development, testing, and production. They are typically used to enable or disable specific functionality in response to changes in the environment.

• Maintenance toggle

  This toggle enables the application to be put into maintenance mode, which can be useful for performing upgrades or fixing critical bugs.

• Feature flag toggle

  This toggle enables the feature flags themselves to be turned on or off. This can be useful for troubleshooting or disabling features that are causing issues.

• Operational toggle

  This toggle enables developers to turn on or off specific functionality in response to changes in the environment, such as an increase in traffic or a change in user behavior. For example, a toggle might be used to disable certain features if the application is experiencing high load.

Example:

if (environment.equals("production") && featureToggle.isEnabled("newFeature")) {
    // Production code here
} else {
    // Development/testing code here
}

1.4. Permission Toggles

Permission toggles control access to specific features or functionality based on user roles, permissions or to a particular user or group of users. They are typically used to enable or disable certain features based on the user's role or permissions.

• Admin toggle

  This toggle enables specific features or functionality to be available only to users with administrative privileges. For example, an admin toggle might be used to give admins access to a dashboard that regular users don't see.

• User role toggle

  This toggle enables specific features or functionality to be available only to users with a particular role or permission level. For example, a user role toggle might be used to give premium users access to additional features that free users don't have.

Example:

if (currentUser.isAdmin() && featureToggle.isEnabled("newFeature")) {
    // Admin-only feature code here
} else {
    // Regular user feature code here
}

1.5. Configuration Toggles

Configuration toggles control the behavior of an application or service based on configuration settings. They are typically used to enable or disable specific functionality based on the environment or configuration of the application.

• Environment toggle

  This toggle enables specific features or functionality to be enabled or disabled based on the environment in which the application is running. For example, a development environment toggle might be used to enable debug mode or disable certain features that are still in development.

• Configuration toggle

  This toggle enables specific features or functionality to be enabled or disabled based on certain configurations or settings. For example, a configuration toggle might be used to enable or disable a feature based on the user's language or location.

Example:

if (configuration.getBoolean("newFeatureEnabled")) {
    // New feature code here
} else {
    // Old feature code here
}

2. Principle

By following these principles, developers can ensure that feature flags are used effectively and do not negatively impact software quality or user experience. Feature flags can be a valuable technique for managing software development and deployment, but their use should be carefully considered and managed to ensure their proper use.

• Plan ahead

  Feature flags should be planned and designed before any coding begins. This ensures that they are integrated into the codebase in a consistent and organized way. It's important to think about the purpose of each toggle, and how it will be used throughout the development cycle.

• Use meaningful names

  Toggle names should be clear and descriptive, so that other developers can easily understand what they do. It's also important to avoid using generic names, such as "flag" or "toggle", which can cause confusion.

• Test thoroughly

  Before deploying a feature toggle, it should be thoroughly tested in a staging or testing environment to ensure that it works as intended. It's important to test all possible scenarios and edge cases, and to have a plan in place for rolling back if something goes wrong.

• Document everything

  All feature flags should be documented in a centralized location, such as a wiki or documentation site. This should include information on the purpose of the toggle, when it was implemented, and who implemented it. This documentation should be kept up to date as the project evolves.

• Remove toggles as soon as possible

  Feature flags should be removed from the codebase as soon as they are no longer needed. This helps to keep the codebase clean and maintainable, and reduces the risk of bugs or conflicts. It's important to have a clear process in place for removing toggles, including testing and deployment procedures.

3. Best Practice

By following these best practices, developers can use feature flags to manage software development in a flexible and efficient way, while minimizing the risk of bugs and conflicts.

• Limit the number of toggles

  Feature flags should be used sparingly and only when necessary. The more toggles there are, the more complex the codebase becomes, and the harder it is to maintain.

• Use feature flags in combination with other techniques

  Feature flags should be used in combination with other techniques, such as continuous integration and continuous deployment, to ensure that new features are delivered in a timely and efficient manner.

• Use version control

  Feature flags should be managed using version control tools, such as Git or SVN, to keep track of changes and make it easy to roll back if something goes wrong.

• Use descriptive names

  Feature flags should be named in a descriptive and meaningful way, so that other developers can easily understand their purpose and function.

• Test thoroughly

  All feature flags should be thoroughly tested before deployment to ensure that they work as intended. This includes testing all possible scenarios and edge cases, and having a plan in place for rolling back if something goes wrong.

• Monitor toggles in production

  Feature flags should be monitored in production to ensure that they are performing as expected and not causing any performance or security issues.

• Remove toggles as soon as possible

  Feature flags should be removed from the codebase as soon as they are no longer needed. This helps to keep the codebase clean and maintainable, and reduces the risk of bugs or conflicts.

4. Terminology

By understanding these terminologies, developers can effectively use feature flags and related deployment strategies to manage software development and releases.

• Toggle

  A toggle is a piece of code that controls the behavior of a feature or functionality. It can be turned on or off to enable or disable the feature.

• Feature flag

  A feature flag is another name for a feature toggle. It is a mechanism for controlling the release and visibility of features in software development.

• Flagsmith

  Flagsmith is an open-source feature flagging and remote configuration platform. It provides a centralized way to manage feature flags, and includes features like multivariate testing and targeting.

5. References

• Martin Fowler feature toggles article.