Update Variant Example Application (#437)

* add example for variant based injection

* readme added

* not use third-party api

* update

* update README

* fix typo

* use latest api

Author: zhiyuanliang-ms

Microsoft.FeatureManagement.sln

@@ -29,7 +29,9 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "EvaluationDataToApplication
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Microsoft.FeatureManagement.Telemetry.ApplicationInsights.AspNetCore", "src\Microsoft.FeatureManagement.Telemetry.ApplicationInsights.AspNetCore\Microsoft.FeatureManagement.Telemetry.ApplicationInsights.AspNetCore.csproj", "{C647611B-A8E5-4AD7-9DBA-60DDE276644B}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "BlazorServerApp", "examples\BlazorServerApp\BlazorServerApp.csproj", "{12BAB5A6-4EEB-4917-B5D9-4AFB6253008E}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "BlazorServerApp", "examples\BlazorServerApp\BlazorServerApp.csproj", "{12BAB5A6-4EEB-4917-B5D9-4AFB6253008E}"
+EndProject
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "VariantServiceDemo", "examples\VariantServiceDemo\VariantServiceDemo.csproj", "{E8E17CB9-434E-4386-BF96-FA53BBFDCD6F}"
 EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
@@ -85,6 +87,10 @@ Global
 		{12BAB5A6-4EEB-4917-B5D9-4AFB6253008E}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{12BAB5A6-4EEB-4917-B5D9-4AFB6253008E}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{12BAB5A6-4EEB-4917-B5D9-4AFB6253008E}.Release|Any CPU.Build.0 = Release|Any CPU
+		{E8E17CB9-434E-4386-BF96-FA53BBFDCD6F}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{E8E17CB9-434E-4386-BF96-FA53BBFDCD6F}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{E8E17CB9-434E-4386-BF96-FA53BBFDCD6F}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{E8E17CB9-434E-4386-BF96-FA53BBFDCD6F}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
@@ -98,6 +104,7 @@ Global
 		{283D3EBB-4716-4F1D-BA51-A435F7E2AB82} = {FB5C34DF-695C-4DF9-8AED-B3EA2516EA72}
 		{1502529E-47E9-4306-98C4-BF6CF7C7C275} = {FB5C34DF-695C-4DF9-8AED-B3EA2516EA72}
 		{12BAB5A6-4EEB-4917-B5D9-4AFB6253008E} = {FB5C34DF-695C-4DF9-8AED-B3EA2516EA72}
+		{E8E17CB9-434E-4386-BF96-FA53BBFDCD6F} = {FB5C34DF-695C-4DF9-8AED-B3EA2516EA72}
 	EndGlobalSection
 	GlobalSection(ExtensibilityGlobals) = postSolution
 		SolutionGuid = {84DA6C54-F140-4518-A1B4-E4CF42117FBD}

README.md

@@ -18,6 +18,7 @@ Feature management provides a way to develop and expose application functionalit
 * [ASP.NET Core Web App (MVC)](./examples/FeatureFlagDemo)
 * [Blazor Server App](./examples/BlazorServerApp)
 * [ASP.NET Core Web App with Feature Flag Telemetry](./examples/EvaluationDataToApplicationInsights)
+* [ASP.NET Core Web App with Variant Service](./examples/VariantServiceDemo)
 
 ## Contributing
 

examples/BlazorServerApp/README.md

@@ -17,34 +17,44 @@ This app demonstrates how to use the Feature Management library in Blazor apps.
 This app uses two feature flags: "BrowserEnhancement" and "Beta".
 
 ``` json
-"FeatureManagement": {
-    "BrowserEnhancement": {
-        "EnabledFor": [
-            {
-                "Name": "Browser",
-                "Parameters": {
-                    "AllowedBrowsers": [ "Edge" ]
-                }
+"feature_management": {
+  "feature_flags": [
+    {
+      "id": "BrowserEnhancement",
+      "enabled": true,
+      "conditions": {
+        "client_filters": [
+          {
+            "name": "Browser",
+            "parameters": {
+              "AllowedBrowsers": [ "Edge" ]
             }
+          }
         ]
+      }
     },
-    "Beta": {
-        "EnabledFor": [
-            {
-                "Name": "Targeting",
-                "Parameters": {
-                    "Audience": {
-                        "DefaultRolloutPercentage": 50,
-                        "Exclusion": {
-                            "Groups": [
-                                "Guests"
-                            ]
-                        }
-                    }
+    {
+      "id": "Beta",
+      "enabled": true,
+      "conditions": {
+        "client_filters": [
+          {
+            "name": "Targeting",
+            "parameters": {
+              "Audience": {
+                "DefaultRolloutPercentage": 50,
+                "Exclusion": {
+                  "Groups": [
+                    "Guests"
+                  ]
                 }
+              }
             }
+          }
         ]
+      }
     }
+  ]
 }
 ```
 
@@ -65,6 +75,7 @@ This app uses [cookie authentication](https://learn.microsoft.com/en-us/aspnet/c
 Rather than `HttpContext`, the [`AuthenticationStateProvider`](https://learn.microsoft.com/en-us/aspnet/core/blazor/security/?view=aspnetcore-8.0#authenticationstateprovider-service) service is used to obtain the user authentication state information for setting targeting context. The details can be found in the [`MyTargetingContextAccessor`](./MyTargetingContextAccessor.cs).
 
 ## Service Registration
+
 Blazor applications like this one typically pull ambient contextual data from scoped services. For example, the `UserAgentContext`, `AuthenticationStateProvider` and `ITargetingContextAccessor` are all scoped services. This pattern *breaks* if the feature management services are added as singleton, which is typical in non-blazor web apps.
 
 In Blazor, *avoid* the following

examples/EvaluationDataToApplicationInsights/Pages/Shared/_Layout.cshtml

@@ -1,11 +1,6 @@
 @using System.Security.Claims
 @using Microsoft.AspNetCore.Http
 
-@inject IHttpContextAccessor httpContextAccessor
-@{
-    string username = httpContextAccessor.HttpContext.Request.Cookies["username"];
-}
-
 <!DOCTYPE html>
 <html lang="en">
 <head>

examples/EvaluationDataToApplicationInsights/Program.cs

@@ -1,9 +1,9 @@
 // Copyright (c) Microsoft Corporation.
 // Licensed under the MIT license.
 //
-using Microsoft.FeatureManagement;
 using EvaluationDataToApplicationInsights;
 using Microsoft.ApplicationInsights.Extensibility;
+using Microsoft.FeatureManagement;
 using Microsoft.FeatureManagement.Telemetry.ApplicationInsights.AspNetCore;
 
 var builder = WebApplication.CreateBuilder(args);
@@ -55,7 +55,7 @@
 app.MapRazorPages();
 
 //
-// Adds Targeting Id to HttpContext
+// Add Targeting Id to HttpContext
 app.UseMiddleware<TargetingHttpContextMiddleware>();
 
 app.Run();

examples/EvaluationDataToApplicationInsights/README.md

@@ -24,9 +24,11 @@ These logs show what would be emitted to a connected Application Insights resour
 To flow these events to Application Insights, [setup a new Application Insights resource in Azure](https://learn.microsoft.com/en-us/azure/azure-monitor/app/create-workspace-resource). Once setup, from `Overview` copy the `Connection String` and place it in `appsettings.json` at ApplicationInsights > ConnectionString. After restarting the app, events should now flow to Application Insights. This [document](https://learn.microsoft.com/en-us/azure/azure-monitor/app/asp-net-core?tabs=netcorenew%2Cnetcore6#enable-application-insights-server-side-telemetry-no-visual-studio) provides more details on connecting a .NET application to Application Insights.
 
 ## About the App
+
 This app uses [Application Insights for ASP.NET Core](https://learn.microsoft.com/en-us/azure/azure-monitor/app/asp-net-core?tabs=netcorenew%2Cnetcore6). This means there is an App Insights SDK in the C# code and a separate App Insights SDK the Javascript. Lets cover what they're doing:
 
 ### Javascript App Insights SDK
+
 See [Enable cliend-side telemetry for web applications](https://learn.microsoft.com/en-us/azure/azure-monitor/app/asp-net-core?tabs=netcorenew%2Cnetcore6#enable-client-side-telemetry-for-web-applications)
 
 For ASP.NET, this is added to _ViewImports.cshtml
@@ -47,11 +49,13 @@ These cookies are used to correlate telemetry from the browser with telemetry fr
 *The Javascript SDK is not required, but is useful for collecting browser telemetry and generating these cookies out of the box.*
 
 ### Targeting Id
+
 In order to connect evaluation events with other metrics from the user, a targeting id needs to be emitted. This can be done multiple ways, but the recommended way is to define a telemetry initializer. This initializer allows the app to modify all telemetry going to Application Insights before it's sent. 
 
 This example uses the provided `TargetingHttpContextMiddleware` and `TargetingTelemetryInitializer`. The middleware adds `TargetingId` (using the targeting context accessor) to the HTTP Context as a request comes in. The initializer checks for the `TargetingId` on the HTTP Context, and if it exists, adds `TargetingId` to all outgoing Application Insights Telemetry.
 
 ## Sample App Usage
+
 Sample steps to try out the app:
 
 1. Run the app. When the app is first started a User Id and Session Id will be generated. The username cookie will be set to a random integer, and the ai_user and ai_session cookies will be expired.

examples/VariantServiceDemo/DefaultCalculator.cs

@@ -0,0 +1,16 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT license.
+//
+using Microsoft.FeatureManagement;
+
+namespace VariantServiceDemo
+{
+    [VariantServiceAlias("DefaultCalculator")]
+    public class DefaultCalculator : ICalculator
+    {
+        public Task<double> AddAsync(double a, double b)
+        {
+            return Task.FromResult(a + b);
+        }
+    }
+}

examples/VariantServiceDemo/HttpContextTargetingContextAccessor.cs

@@ -0,0 +1,53 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT license.
+//
+using Microsoft.FeatureManagement.FeatureFilters;
+
+namespace VariantServiceDemo
+{
+    /// <summary>
+    /// Provides an implementation of <see cref="ITargetingContextAccessor"/> that creates a targeting context using info from the current HTTP request.
+    /// </summary>
+    public class HttpContextTargetingContextAccessor : ITargetingContextAccessor
+    {
+        private const string TargetingContextLookup = "HttpContextTargetingContextAccessor.TargetingContext";
+        private readonly IHttpContextAccessor _httpContextAccessor;
+
+        public HttpContextTargetingContextAccessor(IHttpContextAccessor httpContextAccessor)
+        {
+            _httpContextAccessor = httpContextAccessor ?? throw new ArgumentNullException(nameof(httpContextAccessor));
+        }
+
+        public ValueTask<TargetingContext> GetContextAsync()
+        {
+            HttpContext httpContext = _httpContextAccessor.HttpContext;
+
+            //
+            // Try cache lookup
+            if (httpContext.Items.TryGetValue(TargetingContextLookup, out object value))
+            {
+                return new ValueTask<TargetingContext>((TargetingContext)value);
+            }
+
+            //
+            // Grab username from cookie
+            string username = httpContext.Request.Cookies["username"];
+
+            var groups = new List<string>();
+
+            //
+            // Build targeting context based on user info
+            var targetingContext = new TargetingContext
+            {
+                UserId = username,
+                Groups = groups
+            };
+
+            //
+            // Cache for subsequent lookup
+            httpContext.Items[TargetingContextLookup] = targetingContext;
+
+            return new ValueTask<TargetingContext>(targetingContext);
+        }
+    }
+}

examples/VariantServiceDemo/ICalculator.cs

@@ -0,0 +1,10 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT license.
+//
+namespace VariantServiceDemo
+{
+    public interface ICalculator
+    {
+        public Task<double> AddAsync(double a, double b);
+    }
+}

examples/VariantServiceDemo/Pages/Error.cshtml

@@ -0,0 +1,26 @@
+@page
+@model ErrorModel
+@{
+    ViewData["Title"] = "Error";
+}
+
+<h1 class="text-danger">Error.</h1>
+<h2 class="text-danger">An error occurred while processing your request.</h2>
+
+@if (Model.ShowRequestId)
+{
+    <p>
+        <strong>Request ID:</strong> <code>@Model.RequestId</code>
+    </p>
+}
+
+<h3>Development Mode</h3>
+<p>
+    Swapping to the <strong>Development</strong> environment displays detailed information about the error that occurred.
+</p>
+<p>
+    <strong>The Development environment shouldn't be enabled for deployed applications.</strong>
+    It can result in displaying sensitive information from exceptions to end users.
+    For local debugging, enable the <strong>Development</strong> environment by setting the <strong>ASPNETCORE_ENVIRONMENT</strong> environment variable to <strong>Development</strong>
+    and restarting the app.
+</p>