Targeted Feature does not honor zero percent

[kevink369]

We ran into an issue with the size limit of how many records we could include in a feature (10kb). This helped us realize that we should build an exclude list which would be much smaller and easier to manage. I switched our default rollout percentage to 100% and set the smaller list of records to 0%. We ran into issues when customers that were not supposed to see the new feature were submitting records through the feature.

From the Azure Portal interface:
A Targeting filter is a built-in filter which allows dynamic enabling or disabling of features for specific users or groups. For example, you can use a targeting filter to enable a feature for only a specific user during a demo. You could also use it to progressively roll out new features to users in custom groups or "rings", or to set a default rollout percentage to release features to all users.

We were not able to disable the feature flag in a targeted manor.

Referencing the tests I was able to reproduce the issue with the following scenario (and subsequently tracked down a fix).

"TargetingTestFeatureZeroPercent": {
     "EnabledFor": [
       {
         "Name": "Targeting",
         "Parameters": {
           "Audience": {
             "Users": [
               "Jeff",
               "Alicia"
             ],
             "Groups": [
               {
                 "Name": "Ring0",
                 "RolloutPercentage": 100
               },
               {
                 "Name": "Ring1",
                 "RolloutPercentage": 0
               }
             ],
             "DefaultRolloutPercentage": 100
           }
         }
       }
     ]
   },

[jimmyca15]

Hello @kevink369. This is something we've seen before and is tracked by #123. The current plan to address this is to introduce the capability to specify a deny list of groups/users. anyone in the deny list would never be able to see the feature as enabled.

[kevink369]

Ahh, I missed that one when I looked through the list!

Another option would be to add an else if on:
https://github.com/microsoft/FeatureManagement-Dotnet/blob/main/src/Microsoft.FeatureManagement/Targeting/TargetingEvaluator.cs#L62

The else if could check to see if it is indeed targeted but set to zero percent. Very similar to the function on line 112 but just check that the group rollout is not null and that the RolloutPercentage is zero.

Either way I'm excited that this is being thought about since I'm running into the size limit for targeted groups.

[jimmyca15]

Exclusion was introduced in #218 and is in the latest stable release.