The Journey of Feature Flag Implementation (Build vs. Buy)

Rowan Haddad
June 2, 2021
12 min read
Flagship.ioFeature FlagsThe Journey of Feature Flag Implementation (Build vs. Buy)

The concept of feature flags is quite straightforward and easy to implement, at least at first. In the beginning, you would usually be managing one feature flag by modifying a configuration file but when you start using multiple flags they may become harder to manage and to keep everyone in sync across different functions. 

Undoubtedly, feature flags become increasingly important as engineering and product teams begin to see their benefits. By separating code deployment from feature release, teams can now deliver new functionalities to users safely and quickly.

Feature flags are also extremely versatile and their uses can extend to a number of different scenarios to achieve various tasks by all teams across your organization. As feature flags help developers release faster with lower risk, it makes sense that teams would want to extend their usage across these additional use cases.

We can look at feature flag implementation as a journey that is used initially for one simple use case and which then evolves to more advanced implementations by different stakeholders. This article will illustrate this journey by introducing you to the different use cases of feature flags from simple to more complex and to help you consider whether it is in your best interest to build or buy a feature flag management system according to your goals.

The journey begins with a simple step: if/else statements

A feature flag in a code is essentially an IF statement. Here is a very straightforward, basic example:

Therefore, you can just be starting off with a simple if/else statement, usually reserved for short-lived flags but less so if you’re planning to keep the flag around for a long time or for other more advanced use cases which require more sophistication. Therefore, feature flags have evolved beyond one use case and can serve a variety of purposes. Inserting a few IF statements is easy but it’s actually maintaining a feature flag management system that’s hard work; it requires time, resources and commitment. 

You can implement a feature flag by reading from a config file in order to control which code path will be exposed to your subset of users. Using a config file at the beginning may seem like a viable solution but in the long-term may not be so practical, resulting in technical debt that accumulates over time

Here, a simple flagging solution will not suffice and so you would need to turn to a more advanced solution. Implementing the solution you need in-house can be quite costly and requires a lot of maintenance. In this case, you can turn to a third-party option.

Bumps along the road: Evolving use cases

When you’re just starting out, you’ll implement a feature flag from a config file with an easy on/off toggle to test and roll out new features. Sounds simple enough. Then, one flag turns into 10 or 20 and as you keep adding to these flags leading to the aforementioned technical debt issue as it becomes harder to pinpoint which of your active feature flags need to be removed. In this case, a proactive approach to managing your flags is essential in the form of a comprehensive feature flag management system.

Therefore, at the start of your feature flag journey, you may simply be employing one use case which is experimentation through release management but over time, you may want to implement feature flags across a variety of use cases once you’ve seen first-hand the difference feature flags are making to your releases. 

Test in production

You may for example want to test in production but only internally so you expose the feature to people within your organization. You may also use feature flags to manage entitlements, that is a small subset of users can access your feature, such as users with a premium subscription to your product or service. These types of flags are referred to as permission toggles. So you will need to build a system that can handle different levels of permissions for different users.

Indeed, one of the most important uses for feature flags is the ability to toggle features on or off for a certain subset of users. This use case is referred to as testing in production, which is essential to verify that your feature works as it should in real time and allows you to easily roll back the feature if it turns out to be buggy resulting in safer releases.

To be able to carry out such controlled roll-outs, your feature flagging system should enable you to make such context-specific flagging decisions, for example, for carrying out A/B tests. 

So, for example, you might want to expose your feature to 5, 10 or 15% of your users or you might be looking to test this feature on users from a certain region. A good feature management system provides the means necessary to take such specific contexts when making flagging decisions. Therefore, such contexts can include additional information about the user so here we take into consideration the server handling the request as well as the geographic market the request is linked to.

Choose your players

As a result, feature flags allow you to choose who you want to release your feature to, so the new code can be targeted to a specific group of users whose feedback you need. This would require you to have a system in place that would allow you to perform feature experimentation on those users and attach KPIs to your releases to monitor their reception. However, some companies may not have the time or resources or even experience to collect this kind of rich data.  

Kill switches

Feature flags can be used to kill off non-essential features or disable any broken features in production. Therefore, as soon as your team logs an error, they can easily turn off the feature immediately with the click of a button while your team investigates the issue. This would require your team to have a 2-way communication pathway between monitoring tools and the internal flag system that could be complex to set-up and maintain. The feature can then just as easily be turned on again once it’s ready for deployment. Such kill switches usually require a mature feature flag service implementation platform.

Feature flag hell

We can conclude that when implementing feature flags, you must continuously be aware of the state of each of your feature flags. Otherwise, you could find yourself becoming overwhelmed with the amount of flags in your system leading you to lose control of them when you’re unable to keep track of and maintain them properly. Things could get complicated fast as you add more code to your codebase so you need to make sure that the system you have in place is well-equipped to handle and reduce those costs. 

You’ve probably already come across the term ‘merge hell’ but there’s also such a thing as ‘feature flag hell’. This is basically when you add too many feature flags which can convert your code into the nightmare that is ‘feature flag hell’.

As mentioned above, you can start off with a simple if/else statement but more sophistication will be needed to implement these more advanced use cases.

It is also important to be able to manage the configuration of your in-house system. Any small configuration change can have a major impact on the production environment. Therefore, your system will need to have access controls, audit logs and custom permissions to restrict who can make changes. 

Your system will also need to have an environment-aware configuration that supports a flag configuration from one environment to the next. Most systems should be able to create two kinds of environments: one for development and one for production with its own SDK key. Then you would be able to control the flag’s value depending on which of these environments it’s being used. For example, the flag could be ‘true’ in development but ‘false’ in production. 

Having different environments prevents you from accidentally exposing something in production before you are prepared. When you have all these flags across different environments, it becomes harder to keep everyone in sync, which leads us back to the issue of ‘feature flag hell’ if you don’t have the right system in place.

Feature flags categorization

With such sophisticated use cases, it would not make sense to place feature flags under one category and call it a day. Thus, here we will talk about feature flags when it comes to their longevity and dynamism.

Static vs dynamic

The configuration for some flags will need to be more dynamic than for others. Flipping a toggle can be a simple on/off switch. However, other categories of toggle are more dynamic and will require more sophisticated, very context-specific flagging decisions which are needed for advanced use cases such as A/B testing. For example, permission toggles, usually used for entitlements mentioned earlier, tend to be the most dynamic type of flag as their state depends on the current user and are triggered on a user basis. 

Long- vs short-lived

We can also categorize flags based on how long the decision logic for that flag will remain in the codebase. On the one hand, some flags may be transient in nature, such as release toggles, which can be removed within a few days where the decision logic can be implemented through a simple if/else statement. On the other hand, for flags that will last longer then you’ll need to use more maintainable implementation techniques. Such flags include permission toggles and kill switches.

Therefore, it is important that your feature management solution can keep track of all the flags by determining which flag is which and indicating which flags need to be removed that are no longer needed or in use.

Challenges of an in-house system

As use cases grow so do the challenges of developing an in-house feature flagging system/ Among the challenges organizations face when developing such a system include:

  • Many organizations will start out with a basic implementation where config changes would need to be made manually so the config change for every release will need to be made manually, which is time-consuming. Similarly, when rolling out releases, compiling customer IDs will also be done manually so keeping track of the features rolled out to each user would prove to be a major challenge.
  • Most of these manual processes would be carried out by the engineering team so product managers would be unable to make changes from their end and so will be dependent on engineers to make those changes for them.
  • The preceding point also raises the question of what you want your engineers to devote their time to. Your engineers will need to dedicate a large chunk of their time maintaining your in-house feature flagging tool which could divert their attention from building new features that could drive revenue for your company.
  • This ties to a lack of a UI that could serve as an audit log tracking to monitor when changes are made and by who. The lack of a UI will also mean that only engineers can control feature rollouts while product managers cannot do such deployments themselves or view which features are rolled out to which users. Thus, a centralized dashboard is needed so that all relevant stakeholders can monitor feature impact.
  • As mentioned previously, inability to monitor and clean up old flags will become increasingly difficult as more flags are generated. When flag adoption increases, people across your organization will find it more difficult to track which flags are still active. 

Eventually, if your team does not remove these flags from the system, technical debt would become a major issue. Even keeping track of who created which flag and for what purpose could become a problem if the in-house system doesn’t provide such data. Thus, while the advantages of feature flags are numerous, they will be far outweighed by the technical debt you start to accumulate over time that could slow you down if you are not able to take control and keep track of your feature flags’ lifecycles.

  • There are often high costs associated with maintaining such in-house tools as well as costs associated with upgrades so over time you will see such costs as well as your technical debt accumulating over time. 
  • Such in-house tools are usually built initially to address one pain point so they have minimal functionality and thus cannot be used widely across teams and lack the scalability required to handle a wide range of uses and functions.
  • Time taken to develop feature flag solutions could be time lost you could have spent developing features for your customers so you will need to consider how much time you are willing to dedicate to developing such a system. 

Safe landing: How to proceed

To ensure a safe arrival at the final spot of your feature flag journey (depending on why and how you’re using feature flags), you will need to decide whether in-house or a third-party solution is what’s right for you. With each additional use case, maintaining an in-house solution may become burdensome. In other words, as the scope of the in-house system grows so do the challenges of building and maintaining your in-house system.

Feature flag system is a must

At this point, you may decide that using a third-party feature flag management tool is the right choice for you. Which one you opt for will largely depend on your needs. As already pointed out, implementing your own solution is possible at first but it can be quite costly and troublesome to maintain. 

Keep in mind the following before selecting a feature flag solution:

  • Pain points: what are your goals? What issues are you currently facing in your development and/or production process?
  • Use cases: we’ve already covered the many use cases where feature flags can be employed so you need to consider what you will be using feature flags for. You also need to consider who will be using it (is it just your developers or are there stakeholders involved beyond developers such as Product, Sales, etc?)
  • Carefully weigh the build vs buy solution taking into account factors such as total costs and budget, the scope of your solution (consider the long-term plan of your system), whether there is support across multiple programming languages-the more languages you use, the more tools you will need to support them.

Following the aforementioned points, your feature flagging management system will need to be: stable, scalable, flexible, highly-supported and multi-language compatible.

It’s more than fine to start simple but don’t lose sight of the higher value feature flags can bring to your company, well beyond the use case of decoupling deploy from release. To better manage and monitor your flags, the general consensus is to rely on a feature management system. This will make feature flags management a piece of cake and can help speed up your development process. 

With Flagship by AB Tasty, we take feature flagging to the next level where we offer you more than just switching features on and off, offering high performance and highly scalable managed services. Our solution is catered not just to developers but can be widely used across different teams within your organization. Sign up for a free trial today to learn how you can ship with confidence anytime anywhere.

About the author
Rowan is part of the content marketing team at Flagship by AB Tasty. She's interested in all things marketing, particularly digital marketing. She's also passionate about expanding her knowledge on all things tech.

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