Use variant feature flags
Variant feature flags enable your application to support multiple variants of a feature. The variants of your feature can be assigned to specific users, groups, or percentile buckets. These flags can be useful for feature rollouts, configuration rollouts, and feature experimentation (also known as A/B testing).
What is a variant feature flag?
A variant feature flag is an enhanced feature flag that supports multiple states or variations. While it can still be toggled on or off, it also allows for different variants with configurations. A variant is defined with a Name and an optional Configuration Value. The name is an identifier to tell variants apart. The configuration value can range from simple JSON primitives to complex JSON objects. You can use variants to differentiate functionalities or user experiences and optionally configure these functionalities or user experiences with variant configuration values. Additionally, a variant feature flag includes allocation rules, which define the target audience for each variant.
Variants
The following example shows two variants using JSON objects for the configuration value.
| Variant Name | Variant Configuration Value |
|---|---|
| Minimal | { "maxitems": 10, "showAds": false } |
| Standard | { "maxitems": 30, "showAds": true } |
Allocation
Allocation controls which segment of users get each variant. The following example allocates 10% of users to get the Minimal variant and 90% to get the Standard variant.
| Variant | Allocation | Remarks |
|---|---|---|
| Minimal | 10% | Assign the variant to users in the 0th to 10th percentile. |
| Standard | 90% | Assign the variant to users in the 10th to 100th percentile. |
Overrides
You can assign variants to specific groups or users irrespective of the percentage allocation. The following example assigns users in the Beta Tester group the Minimal variant.
| Group Name | Variant |
|---|---|
| Beta Tester | Minimal |
Default variants and kill switch
Variant feature flags have two variant defaults, DefaultWhenEnabled and DefaultWhenDisabled.
- The DefaultWhenEnabled variant takes effect if the flag is enabled but the allocation doesn't assign all percentiles. Any user placed in an unassigned percentile receives the DefaultWhenEnabled variant.
- The DefaultWhenDisabled variant takes effect if the flag is disabled, done by setting the Enabled field to false, also known as using the "kill switch".
The kill switch is used to stop users from allocating. Used when one or more of the variants have a problem- whether it's a bug, regression, or bad performance. To use the kill switch, set the Enabled field of the variant flag to false. All users now are given the DefaultWhenDisabled variant, regardless of which percentiles or overridden users/groups they were a part of.
Build an app with a variant feature flag
In this tutorial, you create a web app named Quote of the Day. When the app is loaded, it displays a quote. Users can interact with the heart button to like it. To improve user engagement, you want to explore whether a personalized greeting message increases the number of users who like the quote. Users who receive the None variant see no greeting. Users who receive the Simple variant get a simple greeting message. Users who receive the Long variant get a slightly longer greeting.
Prerequisites
- An Azure subscription. If you don’t have one, create one for free.
- An App Configuration store.
Create a variant feature flag
Create a variant feature flag called Greeting with no label in your App Configuration store. It includes three variants: None, Simple, and Long, each corresponding to different greeting messages. Refer to the following table for their configuration values and allocation settings. For more information on how to add a variant feature flag, see Create a variant feature flag.
Variant Name Variant Configuration Value Allocation None (Default) null 50% Simple "Hello!" 25% Long "I hope this makes your day!" 25% Continue to the following instructions to use the variant feature flag in your application for the language or platform you're using.