Remove BackgroundConnectionResetHelper. Fixes #1013

Author: bgrainger

src/MySqlConnector/Core/BackgroundConnectionResetHelper.cs

@@ -66,7 +66,7 @@ public async ValueTask<ServerSession> GetSessionAsync(MySqlConnection connection
 					}
 					else
 					{
-						if ((ConnectionSettings.ConnectionReset && ConnectionSettings.DeferConnectionReset) || session.DatabaseOverride is not null)
+						if (ConnectionSettings.ConnectionReset || session.DatabaseOverride is not null)
 						{
 							reuseSession = await session.TryResetConnectionAsync(ConnectionSettings, null, false, ioBehavior, cancellationToken).ConfigureAwait(false);
 						}
@@ -482,9 +482,6 @@ private async ValueTask<ServerSession> ConnectSessionAsync(string logMessage, in
 				// if we won the race to create the new pool, also store it under the original connection string
 				if (connectionString != normalizedConnectionString)
 					s_pools.GetOrAdd(connectionString, pool);
-
-				if (connectionSettings.ConnectionReset)
-					BackgroundConnectionResetHelper.Start();
 			}
 			else if (pool != newPool && Log.IsDebugEnabled())
 			{
@@ -609,7 +606,6 @@ static ConnectionPool()
 		static void OnAppDomainShutDown(object? sender, EventArgs e)
 		{
 			ClearPoolsAsync(IOBehavior.Synchronous, CancellationToken.None).GetAwaiter().GetResult();
-			BackgroundConnectionResetHelper.Stop();
 		}
 #endif
 

src/MySqlConnector/Core/ConnectionPool.cs

@@ -3,6 +3,7 @@
 using System.IO;
 using System.Net.Security;
 using System.Security.Authentication;
+using MySqlConnector.Logging;
 using MySqlConnector.Utilities;
 
 namespace MySqlConnector.Core
@@ -114,7 +115,10 @@ public ConnectionSettings(MySqlConnectionStringBuilder csb)
 			ConnectionReset = csb.ConnectionReset;
 			ConnectionIdlePingTime = Math.Min(csb.ConnectionIdlePingTime, uint.MaxValue / 1000) * 1000;
 			ConnectionIdleTimeout = (int) csb.ConnectionIdleTimeout;
-			DeferConnectionReset = csb.DeferConnectionReset;
+#pragma warning disable 618
+			if (!csb.DeferConnectionReset)
+				Log.Warn("DeferConnectionReset=false is not supported; using regular connection reset behavior.");
+#pragma warning restore 618
 			if (csb.MinimumPoolSize > csb.MaximumPoolSize)
 				throw new MySqlException("MaximumPoolSize must be greater than or equal to MinimumPoolSize");
 			MinimumPoolSize = ToSigned(csb.MinimumPoolSize);
@@ -211,7 +215,6 @@ private static MySqlGuidFormat GetEffectiveGuidFormat(MySqlGuidFormat guidFormat
 		public bool ConnectionReset { get; }
 		public uint ConnectionIdlePingTime { get; }
 		public int ConnectionIdleTimeout { get; }
-		public bool DeferConnectionReset { get; }
 		public int MinimumPoolSize { get; }
 		public int MaximumPoolSize { get; }
 
@@ -328,6 +331,7 @@ private ConnectionSettings(ConnectionSettings other, string host, int port, stri
 			UseXaTransactions = other.UseXaTransactions;
 		}
 
+		static readonly IMySqlConnectorLogger Log = MySqlConnectorLogManager.CreateLogger(nameof(ConnectionSettings));
 		static readonly string[] s_localhostPipeServer = { "." };
 	}
 }

src/MySqlConnector/Core/ConnectionSettings.cs

@@ -80,12 +80,7 @@ public ValueTask<int> ReturnToPoolAsync(IOBehavior ioBehavior, MySqlConnection?
 				Log.Trace("Session{0} returning to Pool{1}", m_logArguments);
 			}
 			LastReturnedTicks = unchecked((uint) Environment.TickCount);
-			if (Pool is null)
-				return default;
-			if (!Pool.ConnectionSettings.ConnectionReset || Pool.ConnectionSettings.DeferConnectionReset)
-				return Pool.ReturnAsync(ioBehavior, this);
-			BackgroundConnectionResetHelper.AddSession(this, owningConnection);
-			return default;
+			return Pool is null ? default : Pool.ReturnAsync(ioBehavior, this);
 		}
 
 		public bool IsConnected

src/MySqlConnector/Core/ServerSession.cs

@@ -181,6 +181,7 @@ public uint ConnectionIdleTimeout
 			set => MySqlConnectionStringOption.ConnectionIdleTimeout.SetValue(this, value);
 		}
 
+		[Obsolete("This option is no longer supported in MySqlConnector >= 1.4.0.")]
 		public bool DeferConnectionReset
 		{
 			get => MySqlConnectionStringOption.DeferConnectionReset.GetValue(this);

src/MySqlConnector/MySqlConnectionStringBuilder.cs

@@ -36,7 +36,9 @@ public void Defaults()
 			Assert.False(csb.ConnectionReset);
 #else
 			Assert.True(csb.ConnectionReset);
+#pragma warning disable 618
 			Assert.True(csb.DeferConnectionReset);
+#pragma warning restore 618
 #endif
 			Assert.Equal(15u, csb.ConnectionTimeout);
 			Assert.False(csb.ConvertZeroDateTime);
@@ -186,7 +188,9 @@ public void ParseConnectionString()
 			Assert.Equal("My Test Application", csb.ApplicationName);
 			Assert.Equal(60u, csb.ConnectionIdlePingTime);
 			Assert.Equal(30u, csb.ConnectionIdleTimeout);
+#pragma warning disable 618
 			Assert.True(csb.DeferConnectionReset);
+#pragma warning restore 618
 			Assert.True(csb.ForceSynchronous);
 			Assert.True(csb.IgnoreCommandTransaction);
 			Assert.Equal("rsa.pem", csb.ServerRsaPublicKeyFile);

tests/MySqlConnector.Tests/MySqlConnectionStringBuilderTests.cs

@@ -155,9 +155,6 @@ public async Task WaitTimeout()
 			csb.Pooling = true;
 			csb.MinimumPoolSize = 0;
 			csb.MaximumPoolSize = 1;
-#if !BASELINE
-			csb.DeferConnectionReset = true;
-#endif
 			int serverThread;
 
 			using (var connection = new MySqlConnection(csb.ConnectionString))