[Feature Flags] Admin panel improvements (#6895)

Does the following improvements to the feature flags admin panel:

* Adds more debugging information
* Refreshes the gallery's feature flags immediately after saving the flags

Depends on NuGet/ServerCommon#275

Author: loic-sharma

src/NuGetGallery.Core/NuGetGallery.Core.csproj

@@ -221,19 +221,19 @@
   </ItemGroup>
   <ItemGroup>
     <PackageReference Include="NuGet.Services.Entities">
-      <Version>2.42.0</Version>
+      <Version>2.43.0</Version>
     </PackageReference>
     <PackageReference Include="NuGet.Services.FeatureFlags">
-      <Version>2.42.0</Version>
+      <Version>2.43.0</Version>
     </PackageReference>
     <PackageReference Include="NuGet.Services.Messaging.Email">
-      <Version>2.42.0</Version>
+      <Version>2.43.0</Version>
     </PackageReference>
     <PackageReference Include="NuGet.Services.Validation">
-      <Version>2.42.0</Version>
+      <Version>2.43.0</Version>
     </PackageReference>
     <PackageReference Include="NuGet.Services.Validation.Issues">
-      <Version>2.42.0</Version>
+      <Version>2.43.0</Version>
     </PackageReference>
     <PackageReference Include="NuGet.StrongName.AnglicanGeek.MarkdownMailer">
       <Version>1.2.0</Version>

src/NuGetGallery/Areas/Admin/Controllers/FeaturesController.cs

@@ -4,27 +4,45 @@
 using System;
 using System.Threading.Tasks;
 using System.Web.Mvc;
+using NuGet.Services.FeatureFlags;
 using NuGetGallery.Areas.Admin.ViewModels;
+using NuGetGallery.Configuration;
 using NuGetGallery.Features;
 
 namespace NuGetGallery.Areas.Admin.Controllers
 {
     public class FeaturesController : AdminControllerBase
     {
         private readonly IEditableFeatureFlagStorageService _storage;
+        private readonly IFeatureFlagCacheService _cache;
+        private readonly IAppConfiguration _config;
 
-        public FeaturesController(IEditableFeatureFlagStorageService storage)
+        public FeaturesController(
+            IEditableFeatureFlagStorageService storage,
+            IFeatureFlagCacheService cache,
+            IAppConfiguration config)
         {
             _storage = storage ?? throw new ArgumentNullException(nameof(storage));
+            _cache = cache ?? throw new ArgumentNullException(nameof(cache));
+            _config = config ?? throw new ArgumentNullException(nameof(config));
         }
 
         [HttpGet]
         public async virtual Task<ActionResult> Index()
         {
             var reference = await _storage.GetReferenceAsync();
+            var lastUpdated = _cache.GetRefreshTimeOrNull();
+
+            TimeSpan? timeSinceLastRefresh = null;
+            if (lastUpdated.HasValue)
+            {
+                timeSinceLastRefresh = DateTimeOffset.UtcNow.Subtract(lastUpdated.Value);
+            }
 
             return View(new FeatureFlagsViewModel
             {
+                TimeSinceLastRefresh = timeSinceLastRefresh,
+                RefreshInterval = _config.FeatureFlagsRefreshInterval,
                 Flags = reference.FlagsJson,
                 ContentId = reference.ContentId
             });
@@ -41,7 +59,12 @@ public async Task<ActionResult> Index(FeatureFlagsViewModel model)
                 switch (result.Type)
                 {
                     case FeatureFlagSaveResultType.Ok:
-                        TempData["Message"] = "Your feature flags have been saved!";
+                        // The flags have been persisted. Refresh this instance's cache immediately.
+                        await _cache.RefreshAsync();
+
+                        var refreshSeconds = _config.FeatureFlagsRefreshInterval.TotalSeconds;
+
+                        TempData["Message"] = $"Your feature flags have been saved! It may take up to {refreshSeconds} seconds for this change to propagate everywhere.";
                         return Redirect(Url.Action(actionName: "Index", controllerName: "Features"));
 
                     case FeatureFlagSaveResultType.Conflict:

src/NuGetGallery/Areas/Admin/ViewModels/FeatureFlagsViewModel.cs

@@ -1,12 +1,25 @@
 // 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.ComponentModel.DataAnnotations;
 
 namespace NuGetGallery.Areas.Admin.ViewModels
 {
     public class FeatureFlagsViewModel
     {
+        public TimeSpan RefreshInterval { get; set; }
+
+        public TimeSpan? TimeSinceLastRefresh { get; set; }
+
+        public bool IsOutdated
+        {
+            // Ideally, the feature flags refresh instantly at the refresh interval.
+            // To account for random delays, we'll allow for up to a minute of drift before
+            // showing a warning.
+            get => TimeSinceLastRefresh > RefreshInterval.Add(TimeSpan.FromMinutes(1));
+        }
+
         [Required]
         public string Flags { get; set; }
 

src/NuGetGallery/Areas/Admin/Views/Features/Index.cshtml

@@ -7,6 +7,29 @@
 <section role="main" class="container main-container page-revalidation">
     <h1>Feature flags</h1>
 
+    @if (!Model.TimeSinceLastRefresh.HasValue)
+    {
+        @ViewHelpers.AlertWarning(
+            @<text>
+                The feature flags haven't loaded yet. Check the logs for errors.
+            </text>)
+    }
+    else if (Model.IsOutdated)
+    {
+        @ViewHelpers.AlertWarning(
+            @<text>
+                The feature flags were last cached @Math.Round(Model.TimeSinceLastRefresh.Value.TotalSeconds) seconds ago
+                but should refresh every @Model.RefreshInterval.TotalSeconds seconds. Check the logs for errors.
+            </text>)
+    }
+    else
+    {
+        <p>
+            The feature flags were last cached @Math.Round(Model.TimeSinceLastRefresh.Value.TotalSeconds) seconds ago
+            and refresh every @Model.RefreshInterval.TotalSeconds seconds.
+        </p>
+    }
+
     <div class="form-group danger-zone">
         <text>
             @using (Html.BeginForm("Index", "Features", FormMethod.Post))

src/NuGetGallery/NuGetGallery.csproj

@@ -2092,7 +2092,7 @@
       <Version>0.15.4</Version>
     </PackageReference>
     <PackageReference Include="NuGet.Services.Licenses">
-      <Version>2.42.0</Version>
+      <Version>2.43.0</Version>
     </PackageReference>
     <PackageReference Include="NuGet.StrongName.AnglicanGeek.MarkdownMailer">
       <Version>1.2.0</Version>
@@ -2316,16 +2316,16 @@
       <Version>5.0.0-preview1.5665</Version>
     </PackageReference>
     <PackageReference Include="NuGet.Services.KeyVault">
-      <Version>2.42.0</Version>
+      <Version>2.43.0</Version>
     </PackageReference>
     <PackageReference Include="NuGet.Services.Logging">
-      <Version>2.42.0</Version>
+      <Version>2.43.0</Version>
     </PackageReference>
     <PackageReference Include="NuGet.Services.Owin">
-      <Version>2.42.0</Version>
+      <Version>2.43.0</Version>
     </PackageReference>
     <PackageReference Include="NuGet.Services.Sql">
-      <Version>2.42.0</Version>
+      <Version>2.43.0</Version>
     </PackageReference>
     <PackageReference Include="Owin">
       <Version>1.0.0</Version>