[Feature Flags] Add gallery integration (#6806)

Part of https://github.com/NuGet/Engineering/issues/2016

Author: loic-sharma

src/NuGetGallery.Core/CoreConstants.cs

@@ -48,5 +48,7 @@ public static class Folders
         public const string UploadTracingKeyHeaderName = "upload-id";
 
         public const string LicenseFileName = "license";
+
+        public const string FeatureFlagsFileName = "flags.json";
     }
 }

src/NuGetGallery.Core/Features/FeatureFlagClientExtensions.cs

@@ -0,0 +1,40 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using NuGet.Services.Entities;
+using NuGet.Services.FeatureFlags;
+
+namespace NuGetGallery.Features
+{
+    public static class FeatureFlagClientExtensions
+    {
+        public static bool IsEnabled(
+            this IFeatureFlagClient client,
+            string flight,
+            User user,
+            bool defaultValue)
+        {
+            if (user == null)
+            {
+                throw new ArgumentNullException(nameof(user));
+            }
+
+            return client.IsEnabled(flight, new FlightUser(user), defaultValue);
+        }
+
+        private class FlightUser : IFlightUser
+        {
+            public FlightUser(User user)
+            {
+                Username = user.Username;
+                EmailAddress = user.EmailAddress;
+                IsSiteAdmin = user.IsAdministrator;
+            }
+
+            public string Username { get; }
+            public string EmailAddress { get; }
+            public bool IsSiteAdmin { get; }
+        }
+    }
+}

src/NuGetGallery.Core/Features/FeatureFlagFileStorageService.cs

@@ -0,0 +1,33 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.IO;
+using System.Threading.Tasks;
+using Newtonsoft.Json;
+using NuGet.Services.FeatureFlags;
+
+namespace NuGetGallery.Features
+{
+    public class FeatureFlagFileStorageService : IFeatureFlagStorageService
+    {
+        private readonly ICoreFileStorageService _storage;
+        private readonly JsonSerializer _serializer;
+
+        public FeatureFlagFileStorageService(ICoreFileStorageService storage)
+        {
+            _storage = storage ?? throw new ArgumentNullException(nameof(storage));
+            _serializer = new JsonSerializer();
+        }
+
+        public async Task<FeatureFlags> GetAsync()
+        {
+            using (var stream = await _storage.GetFileAsync(CoreConstants.Folders.ContentFolderName, CoreConstants.FeatureFlagsFileName))
+            using (var streamReader = new StreamReader(stream))
+            using (var reader = new JsonTextReader(streamReader))
+            {
+                return _serializer.Deserialize<FeatureFlags>(reader);
+            }
+        }
+    }
+}

src/NuGetGallery.Core/NuGetGallery.Core.csproj

@@ -133,6 +133,8 @@
     <Compile Include="Extensions\StorageExceptionExtensions.cs" />
     <Compile Include="Extensions\UserExtensionsCore.cs" />
     <Compile Include="Extensions\ValidationIssueExtensions.cs" />
+    <Compile Include="Features\FeatureFlagFileStorageService.cs" />
+    <Compile Include="Features\FeatureFlagClientExtensions.cs" />
     <Compile Include="ICloudStorageStatusDependency.cs" />
     <Compile Include="Infrastructure\AzureEntityList.cs" />
     <Compile Include="Infrastructure\ElmahException.cs" />
@@ -214,14 +216,20 @@
     <EmbeddedResource Include="Infrastructure\MigrateUserToOrganization.sql" />
   </ItemGroup>
   <ItemGroup>
+    <PackageReference Include="NuGet.Services.Entities">
+      <Version>2.42.0</Version>
+    </PackageReference>
+    <PackageReference Include="NuGet.Services.FeatureFlags">
+      <Version>2.42.0</Version>
+    </PackageReference>
     <PackageReference Include="NuGet.Services.Messaging.Email">
-      <Version>2.40.0</Version>
+      <Version>2.42.0</Version>
     </PackageReference>
     <PackageReference Include="NuGet.Services.Validation">
-      <Version>2.40.0</Version>
+      <Version>2.42.0</Version>
     </PackageReference>
     <PackageReference Include="NuGet.Services.Validation.Issues">
-      <Version>2.40.0</Version>
+      <Version>2.42.0</Version>
     </PackageReference>
     <PackageReference Include="NuGet.StrongName.AnglicanGeek.MarkdownMailer">
       <Version>1.2.0</Version>

src/NuGetGallery/App_Data/Files/Content/flags.json

@@ -0,0 +1,11 @@
+{
+  "Features": {
+    "NuGetGallery.Typosquatting": "Enabled"
+  },
+
+  "Flights": {
+    "NuGetGallery.TyposquattingFlight": {
+      "All": true
+    }
+  }
+}

src/NuGetGallery/App_Start/DefaultDependenciesModule.cs

@@ -21,6 +21,7 @@
 using Microsoft.Extensions.Logging;
 using Microsoft.WindowsAzure.ServiceRuntime;
 using NuGet.Services.Entities;
+using NuGet.Services.FeatureFlags;
 using NuGet.Services.KeyVault;
 using NuGet.Services.Licenses;
 using NuGet.Services.Logging;
@@ -38,6 +39,7 @@
 using NuGetGallery.Configuration;
 using NuGetGallery.Cookies;
 using NuGetGallery.Diagnostics;
+using NuGetGallery.Features;
 using NuGetGallery.Infrastructure;
 using NuGetGallery.Infrastructure.Authentication;
 using NuGetGallery.Infrastructure.Lucene;
@@ -111,7 +113,11 @@ protected override void Load(ContainerBuilder builder)
             builder.Register(c => configuration.PackageDelete)
                 .As<IPackageDeleteConfiguration>();
 
-            builder.RegisterType<TelemetryService>().As<ITelemetryService>().SingleInstance();
+            builder.RegisterType<TelemetryService>()
+                .As<ITelemetryService>()
+                .As<IFeatureFlagTelemetryService>()
+                .SingleInstance();
+
             builder.RegisterType<CredentialBuilder>().As<ICredentialBuilder>().SingleInstance();
             builder.RegisterType<CredentialValidator>().As<ICredentialValidator>().SingleInstance();
 
@@ -358,6 +364,7 @@ protected override void Load(ContainerBuilder builder)
                 .As<ILicenseExpressionSegmentator>()
                 .InstancePerLifetimeScope();
 
+            RegisterFeatureFlagsService(builder, configuration);
             RegisterMessagingService(builder, configuration);
 
             builder.Register(c => HttpContext.Current.User)
@@ -406,6 +413,32 @@ protected override void Load(ContainerBuilder builder)
             ConfigureAutocomplete(builder, configuration);
         }
 
+        private static void RegisterFeatureFlagsService(ContainerBuilder builder, ConfigurationService configuration)
+        {
+            builder
+                .Register(context => new FeatureFlagOptions
+                {
+                    RefreshInterval = configuration.Current.FeatureFlagsRefreshInterval,
+                })
+                .AsSelf()
+                .SingleInstance();
+
+            builder
+                .RegisterType<FeatureFlagCacheService>()
+                .As<IFeatureFlagCacheService>()
+                .SingleInstance();
+
+            builder
+                .RegisterType<FeatureFlagClient>()
+                .As<IFeatureFlagClient>()
+                .SingleInstance();
+
+            builder
+                .RegisterType<FeatureFlagService>()
+                .As<IFeatureFlagService>()
+                .SingleInstance();
+        }
+
         private static void RegisterMessagingService(ContainerBuilder builder, ConfigurationService configuration)
         {
             if (configuration.Current.AsynchronousEmailServiceEnabled)

src/NuGetGallery/App_Start/OwinStartup.cs

@@ -17,6 +17,7 @@
 using Microsoft.Owin.Logging;
 using Microsoft.Owin.Security;
 using Microsoft.Owin.Security.Cookies;
+using NuGet.Services.FeatureFlags;
 using NuGet.Services.Logging;
 using NuGetGallery.Authentication;
 using NuGetGallery.Authentication.Providers;
@@ -73,7 +74,7 @@ public static void Configuration(IAppBuilder app)
                     await Task.Delay(ContentObjectService.RefreshInterval, token);
                 }
             });
-            
+
             // Setup telemetry
             var instrumentationKey = config.Current.AppInsightsInstrumentationKey;
             if (!string.IsNullOrEmpty(instrumentationKey))
@@ -165,6 +166,14 @@ public static void Configuration(IAppBuilder app)
                 auther.Startup(config, app).Wait();
             }
 
+            // Ensure feature flags are loaded once at startup, and then refresh them in the background.
+            var featureFlags = DependencyResolver.Current.GetService<IFeatureFlagCacheService>();
+            if (featureFlags != null)
+            {
+                featureFlags.RefreshAsync().Wait();
+                HostingEnvironment.QueueBackgroundWorkItem(featureFlags.RunAsync);
+            }
+
             // Catch unobserved exceptions from threads before they cause IIS to crash:
             TaskScheduler.UnobservedTaskException += (sender, exArgs) =>
             {

src/NuGetGallery/App_Start/StorageDependent.cs

@@ -4,7 +4,9 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using NuGet.Services.FeatureFlags;
 using NuGetGallery.Configuration;
+using NuGetGallery.Features;
 
 namespace NuGetGallery
 {
@@ -91,6 +93,7 @@ public static IEnumerable<StorageDependent> GetAll(IAppConfiguration configurati
                 Create<UploadFileService, IUploadFileService>(configuration.AzureStorage_Uploads_ConnectionString, isSingleInstance: false),
                 Create<CoreLicenseFileService, ICoreLicenseFileService>(configuration.AzureStorage_Packages_ConnectionString, isSingleInstance: false),
                 Create<RevalidationStateService, IRevalidationStateService>(configuration.AzureStorage_Revalidation_ConnectionString, isSingleInstance: false),
+                Create<FeatureFlagFileStorageService, IFeatureFlagStorageService>(configuration.AzureStorage_Content_ConnectionString, isSingleInstance: true)
             };
 
             var connectionStringToBindingKey = dependents

src/NuGetGallery/Configuration/AppConfiguration.cs

@@ -67,6 +67,8 @@ public class AppConfiguration : IAppConfiguration
         /// </summary>
         public bool AzureStorageReadAccessGeoRedundant { get; set; }
 
+        public TimeSpan FeatureFlagsRefreshInterval { get; set; }
+
         public bool AsynchronousPackageValidationEnabled { get; set; }
 
         public bool BlockingAsynchronousPackageValidationEnabled { get; set; }

src/NuGetGallery/Configuration/IAppConfiguration.cs

@@ -85,6 +85,11 @@ public interface IAppConfiguration : IMessageServiceConfiguration
         /// </summary>
         bool AzureStorageReadAccessGeoRedundant { get; set; }
 
+        /// <summary>
+        /// How frequently the feature flags should be refreshed.
+        /// </summary>
+        TimeSpan FeatureFlagsRefreshInterval { get; set; }
+
         /// <summary>
         /// Gets a boolean indicating whether asynchronous package validation is enabled.
         /// </summary>