Vastly simplify CDNClientPool

DepotDownloader/CDNClientPool.cs

@@ -2,10 +2,8 @@
 // in file 'LICENSE', which is part of this source code package.
 
 using System;
-using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.Linq;
-using System.Threading;
 using System.Threading.Tasks;
 using SteamKit2.CDN;
 
@@ -16,139 +14,80 @@ namespace DepotDownloader
     /// </summary>
     class CDNClientPool
     {
-        private const int ServerEndpointMinimumSize = 8;
-
         private readonly Steam3Session steamSession;
         private readonly uint appId;
         public Client CDNClient { get; }
         public Server ProxyServer { get; private set; }
 
-        private readonly ConcurrentStack<Server> activeConnectionPool = [];
+        private readonly List<Server> servers = [];
-        private readonly BlockingCollection<Server> availableServerEndpoints = [];
+        private int nextServer;
-
-        private readonly AutoResetEvent populatePoolEvent = new(true);
-        private readonly Task monitorTask;
-        private readonly CancellationTokenSource shutdownToken = new();
-        public CancellationTokenSource ExhaustedToken { get; set; }
 
         public CDNClientPool(Steam3Session steamSession, uint appId)
         {
             this.steamSession = steamSession;
             this.appId = appId;
             CDNClient = new Client(steamSession.steamClient);
-
-            monitorTask = Task.Factory.StartNew(ConnectionPoolMonitorAsync).Unwrap();
         }
 
-        public void Shutdown()
+        public async Task UpdateServerList()
         {
-            shutdownToken.Cancel();
+            var servers = await this.steamSession.steamContent.GetServersForSteamPipe();
-            monitorTask.Wait();
-        }
 
-        private async Task<IReadOnlyCollection<Server>> FetchBootstrapServerListAsync()
+            ProxyServer = servers.Where(x => x.UseAsProxy).FirstOrDefault();
-        {
-            try
-            {
-                var cdnServers = await this.steamSession.steamContent.GetServersForSteamPipe();
-                if (cdnServers != null)
-                {
-                    return cdnServers;
-                }
-            }
-            catch (Exception ex)
-            {
-                Console.WriteLine("Failed to retrieve content server list: {0}", ex.Message);
-            }
 
-            return null;
+            var weightedCdnServers = servers
-        }
+                .Where(server =>
+                {
+                    var isEligibleForApp = server.AllowedAppIds.Length == 0 || server.AllowedAppIds.Contains(appId);
+                    return isEligibleForApp && (server.Type == "SteamCache" || server.Type == "CDN");
+                })
+                .Select(server =>
+                {
+                    AccountSettingsStore.Instance.ContentServerPenalty.TryGetValue(server.Host, out var penalty);
 
-        private async Task ConnectionPoolMonitorAsync()
+                    return (server, penalty);
-        {
+                })
-            var didPopulate = false;
+                .OrderBy(pair => pair.penalty).ThenBy(pair => pair.server.WeightedLoad);
 
-            while (!shutdownToken.IsCancellationRequested)
+            foreach (var (server, weight) in weightedCdnServers)
             {
-                populatePoolEvent.WaitOne(TimeSpan.FromSeconds(1));
+                for (var i = 0; i < server.NumEntries; i++)
-
-                // We want the Steam session so we can take the CellID from the session and pass it through to the ContentServer Directory Service
-                if (availableServerEndpoints.Count < ServerEndpointMinimumSize && steamSession.steamClient.IsConnected)
-                {
-                    var servers = await FetchBootstrapServerListAsync().ConfigureAwait(false);
-
-                    if (servers == null || servers.Count == 0)
-                    {
-                        ExhaustedToken?.Cancel();
-                        return;
-                    }
-
-                    ProxyServer = servers.Where(x => x.UseAsProxy).FirstOrDefault();
-
-                    var weightedCdnServers = servers
-                        .Where(server =>
-                        {
-                            var isEligibleForApp = server.AllowedAppIds.Length == 0 || server.AllowedAppIds.Contains(appId);
-                            return isEligibleForApp && (server.Type == "SteamCache" || server.Type == "CDN");
-                        })
-                        .Select(server =>
-                        {
-                            AccountSettingsStore.Instance.ContentServerPenalty.TryGetValue(server.Host, out var penalty);
-
-                            return (server, penalty);
-                        })
-                        .OrderBy(pair => pair.penalty).ThenBy(pair => pair.server.WeightedLoad);
-
-                    foreach (var (server, weight) in weightedCdnServers)
-                    {
-                        for (var i = 0; i < server.NumEntries; i++)
-                        {
-                            availableServerEndpoints.Add(server);
-                        }
-                    }
-
-                    didPopulate = true;
-                }
-                else if (availableServerEndpoints.Count == 0 && !steamSession.steamClient.IsConnected && didPopulate)
                 {
-                    ExhaustedToken?.Cancel();
+                    this.servers.Add(server);
-                    return;
                 }
             }
-        }
 
-        private Server BuildConnection(CancellationToken token)
+            if (this.servers.Count == 0)
-        {
-            if (availableServerEndpoints.Count < ServerEndpointMinimumSize)
             {
-                populatePoolEvent.Set();
+                throw new Exception("Failed to retrieve any download servers.");
             }
-
-            return availableServerEndpoints.Take(token);
         }
 
-        public Server GetConnection(CancellationToken token)
+        public Server GetConnection()
         {
-            if (!activeConnectionPool.TryPop(out var connection))
+            return servers[nextServer % servers.Count];
-            {
-                connection = BuildConnection(token);
-            }
-
-            return connection;
         }
 
         public void ReturnConnection(Server server)
         {
             if (server == null) return;
 
-            activeConnectionPool.Push(server);
+            // nothing to do, maybe remove from ContentServerPenalty?
         }
 
         public void ReturnBrokenConnection(Server server)
         {
             if (server == null) return;
 
-            // Broken connections are not returned to the pool
+            lock (servers)
+            {
+                if (servers[nextServer % servers.Count] == server)
+                {
+                    nextServer++;
+
+                    // TODO: Add server to ContentServerPenalty
+                }
+            }
         }
     }
 }

DepotDownloader/ContentDownloader.cs

@@ -333,12 +333,6 @@ namespace DepotDownloader
 
         public static void ShutdownSteam3()
         {
-            if (cdnPool != null)
-            {
-                cdnPool.Shutdown();
-                cdnPool = null;
-            }
-
             if (steam3 == null)
                 return;
 
@@ -660,9 +654,9 @@ namespace DepotDownloader
         {
             Ansi.Progress(Ansi.ProgressState.Indeterminate);
 
-            var cts = new CancellationTokenSource();
+            await cdnPool.UpdateServerList();
-            cdnPool.ExhaustedToken = cts;
 
+            var cts = new CancellationTokenSource();
             var downloadCounter = new GlobalDownloadCounter();
             var depotsToDownload = new List<DepotFilesData>(depots.Count);
             var allFileNamesAllDepots = new HashSet<string>();
@@ -759,7 +753,7 @@ namespace DepotDownloader
 
                         try
                         {
-                            connection = cdnPool.GetConnection(cts.Token);
+                            connection = cdnPool.GetConnection();
 
                             string cdnToken = null;
                             if (steam3.CDNAuthTokens.TryGetValue((depot.DepotId, connection.Host), out var authTokenCallbackPromise))
@@ -1202,7 +1196,7 @@ namespace DepotDownloader
 
                     try
                     {
-                        connection = cdnPool.GetConnection(cts.Token);
+                        connection = cdnPool.GetConnection();
 
                         string cdnToken = null;
                         if (steam3.CDNAuthTokens.TryGetValue((depot.DepotId, connection.Host), out var authTokenCallbackPromise))