Question

我尝试在SELECT的表格上运行MySql，我收到此错误：

    Server Error in '/MyApp' Application.
Too many connections
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: MySql.Data.MySqlClient.MySqlException: Too many connections

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.

Stack Trace:


[MySqlException (0x80004005): Too many connections]
   MySql.Data.MySqlClient.MySqlStream.ReadPacket() +517
   MySql.Data.MySqlClient.NativeDriver.Open() +702
   MySql.Data.MySqlClient.Driver.Open() +245
   MySql.Data.MySqlClient.Driver.Create(MySqlConnectionStringBuilder settings) +297
   MySql.Data.MySqlClient.MySqlPool.CreateNewPooledConnection() +18
   MySql.Data.MySqlClient.MySqlPool.GetPooledConnection() +403
   MySql.Data.MySqlClient.MySqlPool.TryToGetDriver() +228
   MySql.Data.MySqlClient.MySqlPool.GetConnection() +106
   MySql.Data.MySqlClient.MySqlConnection.Open() +1468


Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.0.30319.1

我用.net和C＃在iis上运行它。知道如何解决这个问题吗？

这是我如何选择：

MySqlDataReader msdr;

    MySqlConnection connect = new MySqlConnection(connectionStringMySql);
    MySqlCommand cmd = new MySqlCommand();

    string commandLine = "SELECT * FROM Table WHERE active=1;

    commandLine = commandLine.Remove(commandLine.Length - 3);
    cmd.CommandText = commandLine;

    cmd.Connection = connect;
    cmd.Connection.Open();

    msdr = cmd.ExecuteReader();

    while (msdr.Read())
    {
        //Read data
    }

    msdr.Close();
    cmd.Connection.Close();

这是我删除的方式：

                MySqlConnection connect = new MySqlConnection(connectionStringMySql);
                MySqlCommand cmd = new MySqlCommand();

                cmd.Connection = connect;
                cmd.Connection.Open();

                string commandLine = @"DELETE FROM Table WHERE id=@id;";

                cmd.CommandText = commandLine;

                cmd.Parameters.AddWithValue("@id", slotId);

                cmd.ExecuteNonQuery();
                cmd.Connection.Close();

这是我插入的方式：

MySqlConnection connect = new MySqlConnection(connectionStringMySql);
                MySqlCommand cmd = new MySqlCommand();

                cmd.Connection = connect;
                cmd.Connection.Open();

                string commandLine = @"INSERT INTO Table (id, weekday, start, end) VALUES" +
                    "(@ id, @weekday, @start, @end);";

                cmd.CommandText = commandLine;

                cmd.Parameters.AddWithValue("@ id", id);
                cmd.Parameters.AddWithValue("@weekday", item.weekday);
                cmd.Parameters.AddWithValue("@start", new TimeSpan(item.starthour, item.startmin, 0));
                cmd.Parameters.AddWithValue("@end", new TimeSpan(item.endhour, item.endmin, 0));

                cmd.ExecuteNonQuery();
                long id = cmd.LastInsertedId;
                cmd.Connection.Close();
                return id;

Answer 1

上述所有例子都表明了同样的弱点。您不使用using statement来确保关闭和处置连接和其他一次性对象的属性。如果您的一个或多个语句抛出异常，则不会执行关闭连接的代码，并且您可能会以太多连接错误结束

例如

string commandLine = "SELECT * FROM Table WHERE active=1";
commandLine = commandLine.Remove(commandLine.Length - 3);
using(MySqlConnection connect = new MySqlConnection(connectionStringMySql))
using(MySqlCommand cmd = new MySqlCommand(commandLine, connect))
{
    connect.Open();
    using(MySqlDataReader msdr = cmd.ExecuteReader())
    {
        while (msdr.Read())
        {
            //Read data
        }
    }
} // Here the connection will be closed and disposed.  (and the command also)

Answer 2

减少wait_timeout：

[mysqld]
wait_timeout=900

由于ADO.NET使用连接池，即使您将其连接，它也会使您的连接保持活动状态。解决方案是告诉MySQL放弃连接。

C＃MySQL中的连接太多了

2 个答案: