Add cache layer to prevent request throttling under load.

.gitignore

@@ -10,6 +10,7 @@
 *.userosscache
 *.sln.docstates
 appsettings.Development.json
+profile.arm.json
 
 # User-specific files (MonoDevelop/Xamarin Studio)
 *.userprefs

Giants.DataContract/Contracts/PlayerInfo.cs

@@ -1,4 +1,6 @@
-namespace Giants.DataContract
+using System;
+
+namespace Giants.DataContract
 {
     public class PlayerInfo
     {
@@ -11,5 +13,20 @@
         public int Deaths { get; set; }
 
         public string TeamName { get; set; }
+
+        public override bool Equals(object obj)
+        {
+            return obj is PlayerInfo info &&
+                   Index == info.Index &&
+                   Name == info.Name &&
+                   Frags == info.Frags &&
+                   Deaths == info.Deaths &&
+                   TeamName == info.TeamName;
+        }
+
+        public override int GetHashCode()
+        {
+            return HashCode.Combine(Index, Name, Frags, Deaths, TeamName);
+        }
     }
 }

Giants.DataContract/Contracts/ServerInfo.cs

@@ -3,8 +3,7 @@
     using System;
     using System.Collections.Generic;
     using System.ComponentModel.DataAnnotations;
-    using System.Diagnostics.CodeAnalysis;
+    using System.Linq;
-    using System.Text;
 
     public class ServerInfo
     {
@@ -13,12 +12,11 @@
         public string GameName { get; set; }
 
         [Required]
-        [StringLength(100)]
+        public VersionInfo Version { get; set; }
-        public string Version { get; set; }
 
         [Required]
         [StringLength(100)]
-        public string SessionName { get; set; } // was "HostName"
+        public string SessionName { get; set; }
 
         [Required]
         public int Port { get; set; }
@@ -52,5 +50,42 @@
 
         [Required]
         public IList<PlayerInfo> PlayerInfo { get; set; }
+
+        public override bool Equals(object obj)
+        {
+            return obj is ServerInfo info &&
+                   GameName == info.GameName &&
+                   EqualityComparer<VersionInfo>.Default.Equals(Version, info.Version) &&
+                   SessionName == info.SessionName &&
+                   Port == info.Port &&
+                   MapName == info.MapName &&
+                   GameType == info.GameType &&
+                   NumPlayers == info.NumPlayers &&
+                   GameState == info.GameState &&
+                   TimeLimit == info.TimeLimit &&
+                   FragLimit == info.FragLimit &&
+                   TeamFragLimit == info.TeamFragLimit &&
+                   FirstBaseComplete == info.FirstBaseComplete &&
+                   PlayerInfo.SequenceEqual(info.PlayerInfo);
+        }
+
+        public override int GetHashCode()
+        {
+            HashCode hash = new HashCode();
+            hash.Add(GameName);
+            hash.Add(Version);
+            hash.Add(SessionName);
+            hash.Add(Port);
+            hash.Add(MapName);
+            hash.Add(GameType);
+            hash.Add(NumPlayers);
+            hash.Add(GameState);
+            hash.Add(TimeLimit);
+            hash.Add(FragLimit);
+            hash.Add(TeamFragLimit);
+            hash.Add(FirstBaseComplete);
+            hash.Add(PlayerInfo);
+            return hash.ToHashCode();
+        }
     }
 }

Giants.DataContract/Contracts/ServerInfoWithHostAddress.cs

@@ -1,13 +1,26 @@
 namespace Giants.DataContract
 {
     using System;
-    using System.Collections.Generic;
     using System.ComponentModel.DataAnnotations;
-    using System.Text;
 
     public class ServerInfoWithHostAddress : ServerInfo
     {
         [Required]
         public string HostIpAddress { get; set; }
+
+        public override bool Equals(object obj)
+        {
+            return obj is ServerInfoWithHostAddress address &&
+                   base.Equals(obj) &&
+                   HostIpAddress == address.HostIpAddress;
+        }
+
+        public override int GetHashCode()
+        {
+            HashCode hash = new HashCode();
+            hash.Add(base.GetHashCode());
+            hash.Add(HostIpAddress);
+            return hash.ToHashCode();
+        }
     }
 }

Giants.DataContract/Contracts/VersionInfo.cs

@@ -0,0 +1,34 @@
+namespace Giants.DataContract
+{
+    using System;
+    using System.ComponentModel.DataAnnotations;
+
+    public class VersionInfo
+    {
+        [Required]
+        public int Build { get; set; }
+
+        [Required]
+        public int Major { get; set; }
+
+        [Required]
+        public int Minor { get; set; }
+
+        [Required]
+        public int Revision { get; set; }
+
+        public override bool Equals(object obj)
+        {
+            return obj is VersionInfo info &&
+                   Build == info.Build &&
+                   Major == info.Major &&
+                   Minor == info.Minor &&
+                   Revision == info.Revision;
+        }
+
+        public override int GetHashCode()
+        {
+            return HashCode.Combine(Build, Major, Minor, Revision);
+        }
+    }
+}

Giants.Services/Core/CacheKeys.cs

@@ -0,0 +1,11 @@
+namespace Giants.Services
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Text;
+
+    public static class CacheKeys
+    {
+        public const string ServerInfo = nameof(ServerInfo);
+    }
+}

Giants.Services/Core/Entities/ServerInfo.cs

@@ -12,5 +12,23 @@
         public DateTime LastHeartbeat { get; set; }
 
         public string DocumentType => nameof(ServerInfo);
+
+        public override bool Equals(object obj)
+        {
+            return obj is ServerInfo info &&
+                   base.Equals(obj) &&
+                   HostIpAddress == info.HostIpAddress &&
+                   DocumentType == info.DocumentType;
+        }
+
+        public override int GetHashCode()
+        {
+            HashCode hash = new HashCode();
+            hash.Add(base.GetHashCode());
+            hash.Add(id);
+            hash.Add(HostIpAddress);
+            hash.Add(DocumentType);
+            return hash.ToHashCode();
+        }
     }
 }

Giants.Services/Core/ServicesModule.cs

@@ -1,6 +1,7 @@
 namespace Giants.Services
 {
     using Giants.Services.Core;
+    using Microsoft.Extensions.Caching.Memory;
     using Microsoft.Extensions.Configuration;
     using Microsoft.Extensions.DependencyInjection;
 
@@ -11,6 +12,7 @@
             services.AddSingleton<IServerRegistryService, ServerRegistryService>();
             services.AddSingleton<IServerRegistryStore, CosmosDbServerRegistryStore>();
             services.AddSingleton<IDateTimeProvider, DefaultDateTimeProvider>();
+            services.AddSingleton<IMemoryCache, MemoryCache>();
 
             services.AddHostedService<InitializerService>();
             services.AddHostedService<ServerRegistryCleanupService>();

Giants.Services/Giants.Services.csproj

@@ -7,9 +7,12 @@
   <ItemGroup>
     <PackageReference Include="AutoMapper" Version="10.0.0" />
     <PackageReference Include="Microsoft.Azure.Cosmos" Version="3.12.0" />
+    <PackageReference Include="Microsoft.Extensions.Caching.Abstractions" Version="3.1.6" />
+    <PackageReference Include="Microsoft.Extensions.Caching.Memory" Version="3.1.6" />
     <PackageReference Include="Microsoft.Extensions.Configuration" Version="3.1.6" />
     <PackageReference Include="Microsoft.Extensions.DependencyInjection.Abstractions" Version="3.1.6" />
     <PackageReference Include="Microsoft.Extensions.Hosting.Abstractions" Version="3.1.6" />
+    <PackageReference Include="System.Runtime.Caching" Version="4.7.0" />
   </ItemGroup>
 
   <ItemGroup>

Giants.Services/Services/ServerRegistryService.cs

@@ -1,28 +1,38 @@
 namespace Giants.Services
 {
     using System;
+    using System.Collections.Concurrent;
     using System.Collections.Generic;
     using System.Linq;
     using System.Threading.Tasks;
     using Giants.Services.Core;
+    using Microsoft.Extensions.Caching.Memory;
     using Microsoft.Extensions.Configuration;
+    using Microsoft.Extensions.Logging;
 
     public class ServerRegistryService : IServerRegistryService
     {
+        private static readonly string[] SupportedGameNames = new[] { "Giants" };
+        private readonly ILogger<ServerRegistryService> logger;
         private readonly IServerRegistryStore registryStore;
         private readonly IConfiguration configuration;
         private readonly IDateTimeProvider dateTimeProvider;
+        private readonly IMemoryCache memoryCache;
         private readonly TimeSpan timeoutPeriod;
         private readonly int maxServerCount;
 
         public ServerRegistryService(
+            ILogger<ServerRegistryService> logger,
             IServerRegistryStore registryStore,
             IConfiguration configuration,
-            IDateTimeProvider dateTimeProvider)
+            IDateTimeProvider dateTimeProvider,
+            IMemoryCache memoryCache)
         {
+            this.logger = logger;
             this.registryStore = registryStore;
             this.configuration = configuration;
             this.dateTimeProvider = dateTimeProvider;
+            this.memoryCache = memoryCache;
             this.timeoutPeriod = TimeSpan.FromMinutes(Convert.ToDouble(this.configuration["ServerTimeoutPeriodInMinutes"]));
             this.maxServerCount = Convert.ToInt32(this.configuration["MaxServerCount"]);
         }
@@ -33,14 +43,58 @@
             ArgumentUtility.CheckForNull(serverInfo, nameof(serverInfo));
             ArgumentUtility.CheckStringForNullOrEmpty(serverInfo.HostIpAddress, nameof(serverInfo.HostIpAddress));
 
+            if (!SupportedGameNames.Contains(serverInfo.GameName, StringComparer.OrdinalIgnoreCase))
+            {
+                throw new ArgumentException($"Unsupported game name {serverInfo.GameName}", nameof(serverInfo));
+            }
+
+            // Check cache before we write to store
+            ConcurrentDictionary<string, ServerInfo> allServerInfo = await this.memoryCache.GetOrCreateAsync(CacheKeys.ServerInfo, PopulateCache);
+
+            if (allServerInfo.ContainsKey(serverInfo.HostIpAddress))
+            {
+                if (allServerInfo[serverInfo.HostIpAddress].Equals(serverInfo))
+                {
+                    this.logger.LogInformation("State for {IPAddress} is unchanged. Skipping write to store.", serverInfo.HostIpAddress);
+                    return;
+                }
+                else
+                {
+                    this.logger.LogInformation("State for {IPAddress} has changed. Committing update to store.", serverInfo.HostIpAddress);
+                }
+
+            }
             await this.registryStore.UpsertServerInfo(serverInfo);
+
+            this.logger.LogInformation("Updating cache for request from {IPAddress}.", serverInfo.HostIpAddress);
+
+            if (allServerInfo.ContainsKey(serverInfo.HostIpAddress))
+            { 
+                allServerInfo[serverInfo.HostIpAddress] = serverInfo;
+            }
+            else
+            {
+                allServerInfo.TryAdd(serverInfo.HostIpAddress, serverInfo);
+            }
         }
 
         public async Task<IEnumerable<ServerInfo>> GetAllServers()
         {
-            return (await this.registryStore
+            ConcurrentDictionary<string, ServerInfo> serverInfo = await this.memoryCache.GetOrCreateAsync(CacheKeys.ServerInfo, PopulateCache);
+
+            return serverInfo.Values;
+        }
+
+        private async Task<ConcurrentDictionary<string, ServerInfo>> PopulateCache(ICacheEntry entry)
+        {
+            entry.AbsoluteExpirationRelativeToNow = TimeSpan.FromMinutes(1);
+
+            IDictionary<string, ServerInfo> serverInfo = (await this.registryStore
                 .GetServerInfos(whereExpression: c => c.LastHeartbeat > this.dateTimeProvider.UtcNow - this.timeoutPeriod))
-                .Take(this.maxServerCount);
+                .Take(this.maxServerCount)
+                .ToDictionary(x => x.HostIpAddress, y => y);
+
+            return new ConcurrentDictionary<string, ServerInfo>(serverInfo);
         }
     }
 }

Giants.WebApi/Controllers/ServersController.cs

@@ -13,7 +13,7 @@ using Microsoft.Extensions.Logging;
 namespace Giants.Web.Controllers
 {
     [ApiController]
-    [Route("[controller]")]
+    [Route("api/[controller]")]
     public class ServersController : ControllerBase
     {
         private readonly IMapper mapper;