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Feature Flags and How to Use Them in Software Development

By: Mandy Schmitz
  |  March 16, 2023
Feature Flags and How to Use Them in Software Development

Developing software can be a complex and sometimes chaotic process. You need to create, build, test and debug code quickly, while watching for potential problems down the road.

Unfortunately, unless you’re Doctor Strange, you can’t predict the future. There’s no way of telling when clients may ask to add a feature or decide to completely scrap several features. When this happens, you obviously have to make changes to your code. But as a developer, you know too well that changes to the source code may end up rendering it unrunnable.

That’s where feature flags can help. Also called feature toggle, using this feature can be a great strategy for application development. Feature flags enable developers to deploy features safely in progressive stages – adding features gradually and testing each step along the way – plus help you create stable applications that scale over time.

In today’s blog post, we’ll take a look at what feature flags are, how they’re used in software development processes, and when you should implement them as part of your project workflows.

Whether you’re just getting started with coding or have been writing code for years and want to understand how to best use feature flags, this post has got you covered!

What are Feature Flags?

Feature flags refer to a code implementation that gives developers and administrators the ability to quickly turn features on and off in order to customize an application. This enables developers to make changes to the software without having to go through the entire review and development cycle.

For example, if a developer wants to test out a new feature, they can quickly and easily deploy it with a feature flag. Doing this allows them to easily turn the feature off if it’s not working correctly, while other parts of the app remain running and tested. Feature flags also make rolling out new features or taking down old ones much easier without the end user noticing.

With feature flags, teams can commit large chunks of code all at once but only activate pieces when they’re ready for use. This makes app development more agile and allows for greater flexibility when it comes to product changes.

Feature Flags vs. Feature Branches

While they may sound similar, feature flags and feature branches have very distinct differences. 

As I’ve mentioned, feature flags allow teams to turn certain functionality on and off without writing any new code or rewriting the entire source code. 

Feature branches, on the other hand, allow teams to develop and work on new features in their codebase without impacting the main branch – where their code is released from. Feature branches also allow developers to have a log of commits and changes they’ve made to review before merging into the main branch or releasing directly.

In short, feature flags enable developers to separate what users will experience from what’s in development. While feature branches involve testing within a development environment before deploying changes in production.

The Benefits of Using Feature Flags

Since feature flags allow developers to turn functionality on and off without affecting user experiences, they have various benefits.

1. Ensures Continuous Deployment

By reducing the risks associated with deploying updates, feature flags enable developers to continuously deploy revised code while keeping production systems up and running. This, in turn, dramatically reduces the risk of an unsuccessful deployment. So when developers put their work out there, it works.

2. Easier and Faster Migrations

Feature flags make setting up A/B tests, reducing feature rollouts, canarying code, and root cause analysis simpler and more efficient. The ultimate result? A quicker path to launching – or even pausing – any change in the software development cycle without sacrificing reliability. This not only ensures a smooth transition but also helps to reduce the amount of risks associated with deploying new features.

3. Enhances the Agility of Software Development Teams

By using feature flags, software development teams rapidly and safely iterate on code. This makes it much easier to roll out updates in stages and ensures that only well-tested code reaches end users. Because of this, software teams can easily maintain an agile workflow and move faster without sacrificing quality or security.

4. Minimizes Risks and Disruptive Changes

Rather than shooting from the hip with a huge change all at once, feature flagging facilitates making changes incrementally. This helps developers avoid overly disruptive changes and allows quicker identification of any unintended consequences in your apps.

Feature flagging also helps teams gather real-world feedback from actual customers before pushing a feature out into the world. With this, companies can minimize risks while also making sure they still have the ability to innovate quickly and efficiently.

5. More Room for Experimentation

Feature flags offer a controlled way to test out new ideas without committing to code changes. As such, they provide developers with more room for experimentation. Using feature flags, developers can perform A/B tests without destabilizing the production system. And when something goes wrong, the feature flag can simply be disabled with one click – no permanent harm done.

When to Use Feature Flags

Feature flags are especially helpful in the following situations:

1. Soft Rollouts

In soft rollouts, you can use feature flags and slowly introduce a new feature to a small percentage of users before releasing it to everyone. Rather than having to put out a complete update, you can enable or disable certain features as part of the rollout process. This lets you customize the experience, ensuring that users get the most out of what you have to offer. It also allows you to spread out releases across regions for testing times.

2. A/B Testing

A/B testing is a great way to experiment with different features in your software without committing to the changes just yet. But did you know that feature flags can help you take it one step further? 

Feature flags can give you more granular control over which users see different versions, enabling you to fine-tune experiments until you’re ready for launch. When integrated into A/B testing, you can be sure that no matter what version performs best, only the most successful version goes live.

Plus, your stakeholders have visibility into experimental results throughout the process. So everyone involved will have peace of mind when it comes time to push the button.

3. Manage Entitlements

Utilizing feature flags is an effective way to easily manage and modify entitlements within your system. With this, you can easily turn features on or off depending on their users’ entitlements. You can also use feature flags to restrict access to resources and test certain features without risking massive system breakdowns or data loss.

For instance, let’s say you have some top-tier customers whose user entitlements gave them exclusive access to certain features. Feature flagging ensures that those features are locked to anyone else who has not been granted that particular entitlement. 

In short, it’s the perfect way to manage access control policies with precision and simplicity.

4. System Outage (Maintenance or Downtime)

In some cases, system maintenance may result in temporary loss of access to the source code repository or other tools used in the development process. This can impact your ability to make changes or collaborate effectively. 

Plus, if the maintenance involves updates or upgrades to the underlying infrastructure or dependencies, the application’s behavior or performance could be compromised.

By using feature flags, you can target specific user segments with updates or turn off functionality altogether. This targeted approach allows for much faster repairs and can help minimize disruption for other users and customers.

Best of all, if something goes wrong during the process, you don’t have to worry about manually reverting changes. You can simply disable the flag that controls the feature and move on.

5. Continuous Integration

Since feature flags can be used for a wide variety of purposes, they are extremely beneficial when it comes to continuous integration. 

You can use feature flags to safely release new features to selected users, gradually roll out changes to users, test new versions in a production environment and much more. All these help contain changes within decision points instead of affecting the whole codebase. As a result, you’ll find it much easier to continuously integrate new features and changes with fewer risks.

How to Implement Feature Flags

Implementing feature flags can give organizations a greater degree of control over their applications. However, it also presents some logistical and security challenges.

At the most basic level, feature flagging involves deciding which users to give access to new features. This may require technical infrastructure changes on your part. And if you rely on third-party infrastructures, there’s no telling how the new feature will affect performance of the underlying system.

In addition, permissions must be managed carefully to ensure that unauthorized users do not gain access to private or sensitive data. Plus, you need to evaluate what controls should be used to secure each feature flag. All these can give rise to security issues.

Lastly, using feature flags can create logistical issues, such as identifying which features should be flagged and how the moment they’re implemented.

The Implementation Process

To address these, the feature flag implementation process typically involves the following steps:

  • Choosing a feature flag library or tool: There are many open-source and commercial options available, such as LaunchDarkly, Rollout and Unleash.
  • Deciding on the scope of the feature flag: This can be at the code level (e.g., a single feature or bug fix), at the service level (e.g., a whole microservice), or at the application level (e.g., the entire application).
  • Adding the feature flag to the codebase: This involves adding the flag library to your codebase and wrapping the code related to the new feature with a flag check.
  • Controlling the flag’s state: The state of the flag can be managed through a dashboard provided by the flag library, or through APIs and CLI tools.
  • Evaluating the results: Monitor the effects of the new feature on your application’s performance and stability, and make any necessary adjustments to the feature flag or the code itself.
  • Gradually rolling out the feature: Gradually increase the percentage of users who can access the new feature, monitor the results and make any necessary adjustments until the feature is fully rolled out to all users.

Note that the specifics of implementing feature flags will vary depending on the chosen library and the specific requirements of your project.

Avoiding Flag Debts

Feature flags debt happens when a developer adds feature flags but does not take the time to properly remove them from their environment after they are no longer needed. This can cause bloat in the codebase and can lead to bugs, performance issues, redundant code and wasted engineering time on unnecessary maintenance tasks. 

Over time, these issues can create a burden on the development team and slow down the release process. It can also cost a lot in terms of time and resources, as the code needs to be re-visited each time the application is updated or modified.

One way to avoid feature flag debt is to keep the “shelf life” of a flag short. If features are done and ready to be released, they should be deployed quickly, no more than a month after modifications are completed. You should also ensure good communication between teams so everyone remains up-to-date with changes made in any project.

Final Thoughts

Feature flags are a powerful tool that can help improve your software development process. By understanding when and how to use feature flags, you can take advantage of the benefits they provide. Implementing feature flags may require some effort, but the end result will make your team more agile and your life much easier.

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