feature

Feature flag helpers (based on etsy/feature and reddit's config/feature)

Quick Start

Install the NuGet package from the package manager console:

Install-Package Feature

What are feature flags?

Think of feature flags as another configuration item for your app with some special sauce. You can guard your code with a feature flag check and then turn parts of your code on/off based on the feature flag status.

From etsy's docs on the subject:

The Feature API is how we selectively enable and disable features at a very fine grain as well as enabling features for a percentage of users for operational ramp-ups and for A/B tests. A feature can be completely enabled, completely disabled, or something in between and can comprise a number of related variants.

How do I use this?

These tools help you use your existing configuration system to see if a feature is enabled for a given user/group/network, see what variant (if any) a user should get, and get & store Feature flags as JSON data.

It doesn't matter if your config system is built in to .NET, uses tools like Consul or Centralconfig, or is custom built -- you can use this for feature flags.

In short: Store your feature flags in your configuration system as a JSON string and use these utilities to interact with your feature flags.

See if a feature is enabled

A simple example

using FeatureFlags.Library;

if(Feature.IsEnabled(featureFlag))
{
  //  The feature is enabled.
  //  Perform whatever needs to be done for the feature
}

A more complicated example showing all possible parameters

using FeatureFlags.Library;

//  Read in from your configuration system somewhere...
var featureFlag = new FeatureFlag{ Users = new List<string>{ "iserra", "MReynolds"} };

//  Check the flag to see if our current user/group/privs/network mean that the feature is on or off
//  (Don't worry:  almost all of these parameters are optional)
if(Feature.IsEnabled(featureFlag, testUser, testGroup, testUrl, testInternal, testAdmin))
{
  //  The feature is enabled.
  //  Perform whatever needs to be done for the feature

}

//  You can have an else block here...
//  but more likely you'll just proceed as normal

Get a feature flag from a JSON string

using FeatureFlags.Library;

string jsonString = "{\"enabled\": true}";
FeatureFlag retval = jsonString.ToFeatureFlag();

Store a feature flag to a JSON string

using FeatureFlags.Library;

var flag = new FeatureFlag{ Internal = true, Admin = true };
string jsonString = flag.ToJSON();

JSON format

All available options:

{
    "enabled": "true",
    "users": [
        "user1",
        "user2"
    ],
    "groups": [
        "group1",
        "group2"
    ],
    "percent_loggedin": 42,
    "admin": true,
    "internal": true
}

Examples

Completely on

{ "enabled": true}

Completely off

{ "enabled": false}

On for admin

{ "admin": true}

On for internal users/employees

{ "internal": true}

On for certain users

{
    "users": [
        "user1",
        "user2"
    ]
}

On for certain groups

{
    "groups": [
        "group1",
        "group2"
    ]
}

On for a percentage of logged in users (0 being no users, 100 being all of them)

{ "percent_loggedin": 42}

On for both admin and for certain users

{
    "users": [
        "user1",
        "user2"
    ],
    "admin": true
}