环境：
应用程序（用 C# 为 .Net 4 编写）最多有 10 个线程，每个线程在其自己的 AppDomain 中运行。每个线程都使用 ADO.Net DataReader 从 SQL-Server 2008 上的存储过程中获取结果。线程也可以使用 ADO.Net 执行写入操作（批量插入）。一切都在本地机器上运行。
问题 1：
偶尔（大约每 30 次运行）线程的执行速度会急剧下降。这发生在 DataReader 获取存储过程结果 - SqlCommand.ExecuteReader() 时。通常读取操作在 10 秒内执行。当它变慢时，它会在 10-20 分钟内执行。SQLProfiler 显示正在查询数据，尽管速度很慢。
减速的调用栈（请注意没有异常）：
at SNIReadSync(SNI_Conn* , SNI_Packet** , Int32 )
at SNINativeMethodWrapper.SNIReadSync(SafeHandle pConn, IntPtr& packet, Int32 timeout)
at System.Data.SqlClient.TdsParserStateObject.ReadSni(DbAsyncResult asyncResult, TdsParserStateObject stateObj)
at System.Data.SqlClient.TdsParserStateObject.ReadNetworkPacket()
at System.Data.SqlClient.TdsParserStateObject.ReadBuffer()
at System.Data.SqlClient.TdsParserStateObject.ReadByteArray(Byte[] buff, Int32 offset, Int32 len)
at System.Data.SqlClient.TdsParserStateObject.ReadString(Int32 length)
at System.Data.SqlClient.TdsParser.ReadSqlStringValue(SqlBuffer value, Byte type, Int32 length, Encoding encoding, Boolean isPlp, TdsParserStateObject stateObj)
at System.Data.SqlClient.TdsParser.ReadSqlValue(SqlBuffer value, SqlMetaDataPriv md, Int32 length, TdsParserStateObject stateObj)
at System.Data.SqlClient.SqlDataReader.ReadColumnData()
at System.Data.SqlClient.SqlDataReader.ReadColumnHeader(Int32 i)
at System.Data.SqlClient.SqlDataReader.ReadColumn(Int32 i, Boolean setTimeout)
at System.Data.SqlClient.SqlDataReader.GetValueInternal(Int32 i)
at System.Data.SqlClient.SqlDataReader.GetValue(Int32 i)
at System.Data.SqlClient.SqlDataReader.get_Item(String name)
at ****.Core.TableDataImporter.ImportDataFromExcel(Int32 tableId, ExcelEntityLocation location, Boolean& updateResult) in …
问题2：
而不是减慢线程可以挂起。
调用栈：
at SNIReadSync(SNI_Conn* , SNI_Packet** , Int32 )
at SNINativeMethodWrapper.SNIReadSync(SafeHandle pConn, IntPtr& packet, Int32 timeout)
at System.Data.SqlClient.TdsParserStateObject.ReadSni(DbAsyncResult asyncResult, TdsParserStateObject stateObj)
at System.Data.SqlClient.TdsParserStateObject.ReadNetworkPacket()
at System.Data.SqlClient.TdsParserStateObject.ReadBuffer()
at System.Data.SqlClient.TdsParserStateObject.ReadByte()
at System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj)
at System.Data.SqlClient.SqlDataReader.ConsumeMetaData()
at System.Data.SqlClient.SqlDataReader.get_MetaData()
at System.Data.SqlClient.SqlCommand.FinishExecuteReader(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString)
at System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async)
at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, DbAsyncResult result)
at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method)
at System.Data.SqlClient.SqlCommand.ExecuteReader(CommandBehavior behavior, String method)
at System.Data.SqlClient.SqlCommand.ExecuteReader()
调用堆栈是在后台线程中使用调试工具获取的。没有例外，无论是减速还是挂断。
SNIReadSync 是一种在网络级别工作的机制，用于通过网络传输数据包。我们已经在本地机器上重现了这个问题，从等式中消除了网络问题。
我们正在为这种减速/挂断寻找任何输入和解决方案或解决方法。现在我们计划检测减速并重新运行操作。提前致谢。
我根据要求为该方法附加了简化代码：
public void ImportDataFromExcel()
{
try
{
var _сonnectionBuilk = ... ; // singleton connection (at the app level)
var spName = ... ; // stored procedure name
var сonnectionToRead = new SqlConnection(connectionStirng);
сonnectionToRead.Open();
var sqlCommand = new SqlCommand(spName);
sqlCommand.CommandType = CommandType.StoredProcedure;
sqlCommand.Parameters.Add(param1Name, SqlDbType.Int).Value = ...;
sqlCommand.Parameters.Add(param2Name, SqlDbType.Int).Value = ...;
sqlCommand.Parameters.Add(param2Name, SqlDbType.Int).Value = ...;
sqlCommand.Connection = сonnectionToRead;
sqlCommand.CommandTimeout = timeout; // 120 sec
using (var dataReader = sqlCommand.ExecuteReader())
{
dataReader.Read();
.....
int pos1 = dataReader.GetOrdinal(columnName1);
int pos2 = dataReader.GetOrdinal(columnName2);
int pos3 = dataReader.GetOrdinal(columnName3);
int pos4 = dataReader.GetOrdinal(columnName4);
.....
// reading data from sqldatareader
int val1 = dataReader.GetInt32(pos1);
int val2 = dataReader.GetInt32(pos2);
int val3 = dataReader.GetInt32(pos3);
var val4 = dataReader.GetDateTime(pos4);
.....
// append read data into bulkTable
bulkTable.AddCellValue(val1, val2, val3, val4); // bulkTable wraps DataTable, and appends DataRow inside.
if(bulkTable.DataTable.Rows > MaxRowsCount)
{
using (var bulkCopy = new SqlBulkCopy(_сonnectionBuilk))
{
bulkCopy.DestinationTableName = _fullTableName;
bulkCopy.WriteToServer(bulkTable.DataTable);
}
var sqlCommandTransfer = new SqlCommand(spName);
sqlCommandTransfer.CommandType = CommandType.StoredProcedure;
sqlCommandTransfer.Parameters.Add(param1Name, SqlDbType.Int).Value = ...;
sqlCommandTransfer.Connection = _сonnectionBuilk;
....
sqlCommandTransfer.ExecuteNonQuery(); // transfering data from temp bulk table into original table
}
}
}
finally
{
bulkTable.Dispose();
сonnectionToRead.Close();
}
}