Merge pull request #623 from bgrainger/enlist-transaction

Rewrite EnlistTransaction to keep a list of open sessions.

Author: bgrainger

src/MySqlConnector/Core/ImplicitTransactionBase.cs renamed to src/MySqlConnector/Core/EnlistedTransactionBase.cs

@@ -5,15 +5,18 @@
 
 namespace MySqlConnector.Core
 {
-	internal abstract class ImplicitTransactionBase : IEnlistmentNotification
+	internal abstract class EnlistedTransactionBase : IEnlistmentNotification
 	{
-		public MySqlConnection Connection { get; }
+		// A MySqlConnection that holds the ServerSession that was enrolled in the transaction
+		public MySqlConnection Connection { get; set; }
+
+		// Whether the connection is idle, i.e., a client has closed it and is no longer using it
+		public bool IsIdle { get; set; }
 
 		public Transaction Transaction { get; private set; }
 
-		public void Start(Transaction transaction)
+		public void Start()
 		{
-			Transaction = transaction;
 			OnStart();
 			Transaction.EnlistVolatile(this, EnlistmentOptions.None);
 		}
@@ -28,21 +31,25 @@ void IEnlistmentNotification.Commit(Enlistment enlistment)
 		{
 			OnCommit(enlistment);
 			enlistment.Done();
-			Connection.UnenlistTransaction(this, Transaction);
+			Connection.UnenlistTransaction();
 			Transaction = null;
 		}
 
 		void IEnlistmentNotification.Rollback(Enlistment enlistment)
 		{
 			OnRollback(enlistment);
 			enlistment.Done();
-			Connection.UnenlistTransaction(this, Transaction);
+			Connection.UnenlistTransaction();
 			Transaction = null;
 		}
 
 		public void InDoubt(Enlistment enlistment) => throw new NotImplementedException();
 
-		protected ImplicitTransactionBase(MySqlConnection connection) => Connection = connection;
+		protected EnlistedTransactionBase(Transaction transaction, MySqlConnection connection)
+		{
+			Transaction = transaction;
+			Connection = connection;
+		}
 
 		protected abstract void OnStart();
 		protected abstract void OnPrepare(PreparingEnlistment enlistment);

src/MySqlConnector/Core/StandardEnlistedTransaction.cs

@@ -0,0 +1,62 @@
+#if !NETSTANDARD1_3
+using System;
+using System.Transactions;
+using MySql.Data.MySqlClient;
+using MySqlConnector.Utilities;
+
+namespace MySqlConnector.Core
+{
+	internal sealed class StandardEnlistedTransaction : EnlistedTransactionBase
+	{
+		public StandardEnlistedTransaction(Transaction transaction, MySqlConnection connection)
+			: base(transaction, connection)
+		{
+		}
+
+		protected override void OnStart()
+		{
+			string isolationLevel;
+			switch (Transaction.IsolationLevel)
+			{
+			case IsolationLevel.Serializable:
+				isolationLevel = "serializable";
+				break;
+			case IsolationLevel.ReadCommitted:
+				isolationLevel = "read committed";
+				break;
+			case IsolationLevel.ReadUncommitted:
+				isolationLevel = "read uncommitted";
+				break;
+			case IsolationLevel.Snapshot:
+			case IsolationLevel.Chaos:
+				throw new NotSupportedException("IsolationLevel.{0} is not supported.".FormatInvariant(Transaction.IsolationLevel));
+			// "In terms of the SQL:1992 transaction isolation levels, the default InnoDB level is REPEATABLE READ." - http://dev.mysql.com/doc/refman/5.7/en/innodb-transaction-model.html
+			case IsolationLevel.Unspecified:
+			case IsolationLevel.RepeatableRead:
+			default:
+				isolationLevel = "repeatable read";
+				break;
+			}
+
+			using (var cmd = new MySqlCommand("set transaction isolation level " + isolationLevel + "; start transaction;", Connection))
+				cmd.ExecuteNonQuery();
+		}
+
+		protected override void OnPrepare(PreparingEnlistment enlistment)
+		{
+		}
+
+		protected override void OnCommit(Enlistment enlistment)
+		{
+			using (var cmd = new MySqlCommand("commit;", Connection))
+				cmd.ExecuteNonQuery();
+		}
+
+		protected override void OnRollback(Enlistment enlistment)
+		{
+			using (var cmd = new MySqlCommand("rollback;", Connection))
+				cmd.ExecuteNonQuery();
+		}
+	}
+}
+#endif

src/MySqlConnector/Core/StandardImplicitTransaction.cs

@@ -6,10 +6,10 @@
 
 namespace MySqlConnector.Core
 {
-	internal sealed class XaImplicitTransaction : ImplicitTransactionBase
+	internal sealed class XaEnlistedTransaction : EnlistedTransactionBase
 	{
-		public XaImplicitTransaction(MySqlConnection connection)
-			: base(connection)
+		public XaEnlistedTransaction(Transaction transaction, MySqlConnection connection)
+			: base(transaction, connection)
 		{
 		}