Description:
MySql Server version: 5.0.51a-community.
When calling MySqlConnection.Close() it fails with a null reference exception.
The connection is in a transaction. The network to the server goes down just before commiting the transaction. The commit fails (correctly) due to this, just before Close() is called.
Expected behaviour: MySqlConnection.Close() fails with a MySqlException.
I will soon file a related bug on the server which is much more critical and triggered by this.
How to repeat:
Prerequisities: The database server is not on the same machine as this test is run on.
1) Create a table:
CREATE TABLE `test` (
`id` bigint(20) NOT NULL auto_increment,
`value` int(11) NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=INNODB AUTO_INCREMENT=1 DEFAULT CHARSET=latin1;
2) Create a small test application (for example a windows application with two buttons), with the following code:
private void button3_Click(object sender, EventArgs e)
{
_conn = new MySqlConnection("server=servername;Port=port;database=dbname;user id=user;password=password;pooling=true;");
_conn.Open();
_trans = _conn.BeginTransaction();
using (MySqlCommand cmd = new MySqlCommand("insert into test (value) values (2);", _conn))
{
cmd.ExecuteNonQuery();
}
}
private void button4_Click(object sender, EventArgs e)
{
try
{
_trans.Commit();
}
catch (Exception ex)
{
Console.WriteLine("Exception when commiting:");
Console.WriteLine(ex.ToString());
}
try
{
_conn.Close();
}
catch (Exception ex2)
{
Console.WriteLine("Exception when closing conn:");
Console.WriteLine(ex2.ToString());
}
}
3) Replace connection information in the connection string with real values, but make sure "pooling=true" is still there (or is it true by default?).
4) Start the program and trigger the "button3_Click" method.
5) Disable the network connection in windows.
6) Trigger the "button4_Click" method.
You'll get an output like this:
A first chance exception of type 'MySql.Data.MySqlClient.MySqlException' occurred in MySql.Data.dll
Exception when commiting:
MySql.Data.MySqlClient.MySqlException: Writing to the stream failed. ---> System.IO.IOException: Unable to write data to the transport connection: En befintlig anslutning tvingades att stänga av fjärrvärddatorn. ---> System.Net.Sockets.SocketException: En befintlig anslutning tvingades att stänga av fjärrvärddatorn
at System.Net.Sockets.Socket.Send(Byte[] buffer, Int32 offset, Int32 size, SocketFlags socketFlags)
at System.Net.Sockets.NetworkStream.Write(Byte[] buffer, Int32 offset, Int32 size)
--- End of inner exception stack trace ---
at System.Net.Sockets.NetworkStream.Write(Byte[] buffer, Int32 offset, Int32 size)
at System.IO.BufferedStream.FlushWrite()
at System.IO.BufferedStream.Flush()
at MySql.Data.MySqlClient.MySqlStream.Flush()
--- End of inner exception stack trace ---
at MySql.Data.MySqlClient.MySqlStream.Flush()
at MySql.Data.MySqlClient.NativeDriver.ExecuteCommand(DBCmd cmd, Byte[] bytes, Int32 length)
at MySql.Data.MySqlClient.NativeDriver.Query(Byte[] bytes, Int32 length)
at MySql.Data.MySqlClient.Statement.ExecuteNext()
at MySql.Data.MySqlClient.PreparableStatement.ExecuteNext()
at MySql.Data.MySqlClient.Statement.Execute()
at MySql.Data.MySqlClient.PreparableStatement.Execute()
at MySql.Data.MySqlClient.MySqlCommand.ExecuteReader(CommandBehavior behavior)
at MySql.Data.MySqlClient.MySqlCommand.ExecuteReader()
at MySql.Data.MySqlClient.MySqlCommand.ExecuteNonQuery()
at MySql.Data.MySqlClient.MySqlTransaction.Commit()
at MySqlConnectorTransactionLockTest.Form1.button4_Click(Object sender, EventArgs e) in Form1.cs:line 94
A first chance exception of type 'System.NullReferenceException' occurred in MySql.Data.dll
Exception when closing conn:
System.NullReferenceException: Object reference not set to an instance of an object.
at MySql.Data.MySqlClient.NativeDriver.ExecuteCommand(DBCmd cmd, Byte[] bytes, Int32 length)
at MySql.Data.MySqlClient.NativeDriver.Query(Byte[] bytes, Int32 length)
at MySql.Data.MySqlClient.Statement.ExecuteNext()
at MySql.Data.MySqlClient.PreparableStatement.ExecuteNext()
at MySql.Data.MySqlClient.Statement.Execute()
at MySql.Data.MySqlClient.PreparableStatement.Execute()
at MySql.Data.MySqlClient.MySqlCommand.ExecuteReader(CommandBehavior behavior)
at MySql.Data.MySqlClient.MySqlCommand.ExecuteReader()
at MySql.Data.MySqlClient.MySqlCommand.ExecuteNonQuery()
at MySql.Data.MySqlClient.MySqlTransaction.Rollback()
at MySql.Data.MySqlClient.MySqlConnection.CloseFully()
at MySql.Data.MySqlClient.MySqlConnection.Close()
at MySqlConnectorTransactionLockTest.Form1.button4_Click(Object sender, EventArgs e) in Form1.cs:line 104
Expected result:
A similar output, but with MySqlException instead of NullReferenceException.
Suggested fix:
Analyze why the unexpected state in the NativeDriver occurs and fix it.
Description: MySql Server version: 5.0.51a-community. When calling MySqlConnection.Close() it fails with a null reference exception. The connection is in a transaction. The network to the server goes down just before commiting the transaction. The commit fails (correctly) due to this, just before Close() is called. Expected behaviour: MySqlConnection.Close() fails with a MySqlException. I will soon file a related bug on the server which is much more critical and triggered by this. How to repeat: Prerequisities: The database server is not on the same machine as this test is run on. 1) Create a table: CREATE TABLE `test` ( `id` bigint(20) NOT NULL auto_increment, `value` int(11) NOT NULL, PRIMARY KEY (`id`) ) ENGINE=INNODB AUTO_INCREMENT=1 DEFAULT CHARSET=latin1; 2) Create a small test application (for example a windows application with two buttons), with the following code: private void button3_Click(object sender, EventArgs e) { _conn = new MySqlConnection("server=servername;Port=port;database=dbname;user id=user;password=password;pooling=true;"); _conn.Open(); _trans = _conn.BeginTransaction(); using (MySqlCommand cmd = new MySqlCommand("insert into test (value) values (2);", _conn)) { cmd.ExecuteNonQuery(); } } private void button4_Click(object sender, EventArgs e) { try { _trans.Commit(); } catch (Exception ex) { Console.WriteLine("Exception when commiting:"); Console.WriteLine(ex.ToString()); } try { _conn.Close(); } catch (Exception ex2) { Console.WriteLine("Exception when closing conn:"); Console.WriteLine(ex2.ToString()); } } 3) Replace connection information in the connection string with real values, but make sure "pooling=true" is still there (or is it true by default?). 4) Start the program and trigger the "button3_Click" method. 5) Disable the network connection in windows. 6) Trigger the "button4_Click" method. You'll get an output like this: A first chance exception of type 'MySql.Data.MySqlClient.MySqlException' occurred in MySql.Data.dll Exception when commiting: MySql.Data.MySqlClient.MySqlException: Writing to the stream failed. ---> System.IO.IOException: Unable to write data to the transport connection: En befintlig anslutning tvingades att stänga av fjärrvärddatorn. ---> System.Net.Sockets.SocketException: En befintlig anslutning tvingades att stänga av fjärrvärddatorn at System.Net.Sockets.Socket.Send(Byte[] buffer, Int32 offset, Int32 size, SocketFlags socketFlags) at System.Net.Sockets.NetworkStream.Write(Byte[] buffer, Int32 offset, Int32 size) --- End of inner exception stack trace --- at System.Net.Sockets.NetworkStream.Write(Byte[] buffer, Int32 offset, Int32 size) at System.IO.BufferedStream.FlushWrite() at System.IO.BufferedStream.Flush() at MySql.Data.MySqlClient.MySqlStream.Flush() --- End of inner exception stack trace --- at MySql.Data.MySqlClient.MySqlStream.Flush() at MySql.Data.MySqlClient.NativeDriver.ExecuteCommand(DBCmd cmd, Byte[] bytes, Int32 length) at MySql.Data.MySqlClient.NativeDriver.Query(Byte[] bytes, Int32 length) at MySql.Data.MySqlClient.Statement.ExecuteNext() at MySql.Data.MySqlClient.PreparableStatement.ExecuteNext() at MySql.Data.MySqlClient.Statement.Execute() at MySql.Data.MySqlClient.PreparableStatement.Execute() at MySql.Data.MySqlClient.MySqlCommand.ExecuteReader(CommandBehavior behavior) at MySql.Data.MySqlClient.MySqlCommand.ExecuteReader() at MySql.Data.MySqlClient.MySqlCommand.ExecuteNonQuery() at MySql.Data.MySqlClient.MySqlTransaction.Commit() at MySqlConnectorTransactionLockTest.Form1.button4_Click(Object sender, EventArgs e) in Form1.cs:line 94 A first chance exception of type 'System.NullReferenceException' occurred in MySql.Data.dll Exception when closing conn: System.NullReferenceException: Object reference not set to an instance of an object. at MySql.Data.MySqlClient.NativeDriver.ExecuteCommand(DBCmd cmd, Byte[] bytes, Int32 length) at MySql.Data.MySqlClient.NativeDriver.Query(Byte[] bytes, Int32 length) at MySql.Data.MySqlClient.Statement.ExecuteNext() at MySql.Data.MySqlClient.PreparableStatement.ExecuteNext() at MySql.Data.MySqlClient.Statement.Execute() at MySql.Data.MySqlClient.PreparableStatement.Execute() at MySql.Data.MySqlClient.MySqlCommand.ExecuteReader(CommandBehavior behavior) at MySql.Data.MySqlClient.MySqlCommand.ExecuteReader() at MySql.Data.MySqlClient.MySqlCommand.ExecuteNonQuery() at MySql.Data.MySqlClient.MySqlTransaction.Rollback() at MySql.Data.MySqlClient.MySqlConnection.CloseFully() at MySql.Data.MySqlClient.MySqlConnection.Close() at MySqlConnectorTransactionLockTest.Form1.button4_Click(Object sender, EventArgs e) in Form1.cs:line 104 Expected result: A similar output, but with MySqlException instead of NullReferenceException. Suggested fix: Analyze why the unexpected state in the NativeDriver occurs and fix it.