Add more logging for cancellation.

Author: bgrainger

src/MySqlConnector/Core/ServerSession.cs

@@ -113,18 +113,22 @@ public bool TryStartCancel(ICancellableCommand command)
 
 		public void DoCancel(ICancellableCommand commandToCancel, MySqlCommand killCommand)
 		{
-			Log.Info("Session{0} canceling CommandId {1}: CommandText: {2}", m_logArguments[0], commandToCancel.CommandId, (commandToCancel as MySqlCommand)?.CommandText);
+			Log.Info("Session{0} canceling CommandId {1} from Session{2}; CommandText: {3}", m_logArguments[0], commandToCancel.CommandId, killCommand.Connection!.Session.Id, (commandToCancel as MySqlCommand)?.CommandText);
 			lock (m_lock)
 			{
 				if (ActiveCommandId != commandToCancel.CommandId)
+				{
+					Log.Info("Session{0} ActiveCommandId {1} is not the CommandId {2} being canceled; ignoring cancellation.", m_logArguments[0], ActiveCommandId, commandToCancel.CommandId);
 					return;
+				}
 
 				// NOTE: This command is executed while holding the lock to prevent race conditions during asynchronous cancellation.
 				// For example, if the lock weren't held, the current command could finish and the other thread could set ActiveCommandId
 				// to zero, then start executing a new command. By the time this "KILL QUERY" command reached the server, the wrong
 				// command would be killed (because "KILL QUERY" specifies the connection whose command should be killed, not
 				// a unique identifier of the command itself). As a mitigation, we set the CommandTimeout to a low value to avoid
 				// blocking the other thread for an extended duration.
+				Log.Info("Session{0} canceling CommandId {1} with CommandText {2}", killCommand.Connection!.Session.Id, commandToCancel.CommandId, killCommand.CommandText);
 				killCommand.ExecuteNonQuery();
 			}
 		}

src/MySqlConnector/MySqlCommand.cs

@@ -6,6 +6,7 @@
 using System.Threading;
 using System.Threading.Tasks;
 using MySqlConnector.Core;
+using MySqlConnector.Logging;
 using MySqlConnector.Protocol.Serialization;
 using MySqlConnector.Utilities;
 
@@ -94,7 +95,11 @@ private MySqlCommand(MySqlCommand other)
 		public new MySqlParameter CreateParameter() => (MySqlParameter) base.CreateParameter();
 
 		/// <inheritdoc/>
-		public override void Cancel() => Connection?.Cancel(this);
+		public override void Cancel()
+		{
+			Log.Info("CommandId {0} for Session{1} has been canceled via Cancel().", m_commandId, Connection?.Session.Id);
+			Connection?.Cancel(this);
+		}
 
 		/// <inheritdoc/>
 		public override int ExecuteNonQuery() => ExecuteNonQueryAsync(IOBehavior.Synchronous, CancellationToken.None).GetAwaiter().GetResult();
@@ -387,8 +392,9 @@ void ICancellableCommand.SetTimeout(int milliseconds)
 
 		private void CancelCommandForTimeout()
 		{
+			Log.Info("CommandId {0} for Session{1} has been canceled via command timeout.", m_commandId, Connection?.Session.Id);
 			Volatile.Write(ref m_commandTimedOut, true);
-			Cancel();
+			Connection?.Cancel(this);
 		}
 
 		private bool IsValid([NotNullWhen(false)] out Exception? exception)
@@ -414,6 +420,8 @@ private bool IsValid([NotNullWhen(false)] out Exception? exception)
 		MySqlParameterCollection? IMySqlCommand.OutParameters { get; set; }
 		MySqlParameter? IMySqlCommand.ReturnParameter { get; set; }
 
+		static readonly IMySqlConnectorLogger Log = MySqlConnectorLogManager.CreateLogger(nameof(MySqlCommand));
+
 		readonly int m_commandId;
 		bool m_isDisposed;
 		MySqlConnection? m_connection;