Imap client pool improvements and implementation of MaxConcurrentClients.

Wino.Core/Integration/ImapClientPool.cs

@@ -9,6 +9,7 @@ using MailKit;
 using MailKit.Net.Imap;
 using MailKit.Net.Proxy;
 using MailKit.Security;
+using MoreLinq;
 using Serilog;
 using Wino.Core.Domain.Entities;
 using Wino.Core.Domain.Enums;
@@ -39,10 +40,10 @@ namespace Wino.Core.Integration
             Vendor = "Wino"
         };
 
-        private const int MaxPoolSize = 5;
+        private readonly int MinimumPoolSize = 5;
 
-        private readonly ConcurrentBag<ImapClient> _clients = [];
-        private readonly SemaphoreSlim _semaphore = new(MaxPoolSize);
+        private readonly ConcurrentStack<ImapClient> _clients = [];
+        private readonly SemaphoreSlim _semaphore;
         private readonly CustomServerInformation _customServerInformation;
         private readonly Stream _protocolLogStream;
         private readonly ILogger _logger = Log.ForContext<ImapClientPool>();
@@ -51,6 +52,9 @@ namespace Wino.Core.Integration
         {
             _customServerInformation = customServerInformation;
             _protocolLogStream = protocolLogStream;
+
+            // Set the maximum pool size to 5 or the custom value if it's greater.
+            _semaphore = new(Math.Max(MinimumPoolSize, customServerInformation.MaxConcurrentClients));
         }
 
         private async Task EnsureConnectivityAsync(ImapClient client, bool isCreatedNew)
@@ -126,7 +130,7 @@ namespace Wino.Core.Integration
         {
             await _semaphore.WaitAsync();
 
-            if (_clients.TryTake(out ImapClient item))
+            if (_clients.TryPop(out ImapClient item))
             {
                 await EnsureConnectivityAsync(item, false);
 
@@ -140,16 +144,37 @@ namespace Wino.Core.Integration
             return client;
         }
 
-        public void Release(ImapClient item)
+        public void Release(ImapClient item, bool destroyClient = false)
         {
             if (item != null)
             {
-                _clients.Add(item);
+                if (destroyClient)
+                {
+                    lock (item.SyncRoot)
+                    {
+                        item.Disconnect(true);
+                    }
+
+                    item.Dispose();
+                }
+                else
+                {
+                    _clients.Push(item);
+                }
+
                 _semaphore.Release();
             }
         }
 
-        public ImapClient CreateNewClient()
+        public void DestroyClient(ImapClient client)
+        {
+            if (client == null) return;
+
+            client.Disconnect(true);
+            client.Dispose();
+        }
+
+        private ImapClient CreateNewClient()
         {
             ImapClient client = null;
 
@@ -232,11 +257,20 @@ namespace Wino.Core.Integration
 
         public void Dispose()
         {
-            foreach (var client in _clients)
+            _clients.ForEach(client =>
+            {
+                lock (client.SyncRoot)
+                {
+                    client.Disconnect(true);
+                }
+            });
+
+            _clients.ForEach(client =>
             {
-                client.Disconnect(true);
                 client.Dispose();
-            }
+            });
+
+            _clients.Clear();
 
             if (_protocolLogStream != null)
             {

Wino.Core/Services/ImapTestService.cs

@@ -45,8 +45,7 @@ namespace Wino.Core.Services
                 // This call will make sure that everything is authenticated + connected successfully.
                 var client = await clientPool.GetClientAsync();
 
-                await client.DisconnectAsync(true);
-                client.Dispose();
+                clientPool.Release(client);
             }
         }
     }