Connection Pooling Problem?
From: Bob (anonymous_at_discussions.microsoft.com)
Date: 05/19/04
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Date: Tue, 18 May 2004 18:26:03 -0700
I have an ASP.NET web application that has been running without any problems for a while. I recently transferred the site to shared hosting and had multiple users start to use the site. The problem I'm experiencing is that when many users are hitting the site at once, occasionaly I will see errors. The 3 most common ones are: "The SqlCommand is currently busy Open, Fetching. ", "Internal Connection Fatal Error", "object reference not set to an instance of an object".
In addition, occassionally the application will lockup for hours after one of these errors. I can navigate to pages, but I cannot log in to my application - I get a "request timed out" error. It usually seems to go away after a few hours - but obviosuly this is very weird behavior.
The research I have done so far indicates that the "The SqlCommand is currently busy Open, Fetching." error usually occurs because a connection that was not properly closed is returned to the connection pool or is accessed when it is still outside the pool (and open) because multiple users are hitting it at the same time. The article I've seen about this (http://www.experts-exchange.com/Programming/Programming_Languages/Dot_Net/Q_20942137.html) mentioned someone putting his data access components in a module, and the accepted solution was to put everything in a class.
However, the Data Access Layer design I'm using has worked in several other multi-user web applications, so it is odd that this is happening. I am using InProcess session state, and other than that I don't know what other configuration setting might be affecting this. Could this be an IIS or hardware configuration problem? It is impossible to replicate this in debug mode because it only happens when multiple users hit the system. Anyway, thanks in advance for the help.
Here is one of the methods where the "SqlCommand is currently busy Open, Fetching" error occurred:
public void GetAllRestaurantsByGroup(RestaurantCollection col, int groupid)
{
try
{
Connect();
PrepareCommand("Restaurant_Select_All_By_Group");
m_dsoCommand.AddParameters("@group_id", groupid);
return m_dsoCommand.ExecuteReader();
while (m_sqlReader.Read())
{
Restaurant oRestaurant = new Restaurant();
oRestaurant.RestaurantName = (string)m_sqlReader["restaurantname"];
oRestaurant.GroupID = (int)m_sqlReader["groupid"];
oRestaurant.LastVisit = (System.DateTime)m_sqlReader["lastvisit"];
oRestaurant.Description = (string)m_sqlReader["description"];
oRestaurant.Distance = (double)m_sqlReader["distance"];
oRestaurant.MapURL = (string)m_sqlReader["MapURL"];
oRestaurant.DBBacked = true;
col.Add(oRestaurant);
}
}
catch(Exception e)
{
throw e;
}
finally
{
Disconnect();
}
}
The code called by this method is below:
protected DSOConnection m_dsoConnection;
protected SqlDataReader m_sqlReader;
public void Connect()
{
try
{
m_dsoConnection.Open();
}
catch(Exception e)
{
throw e;
}
}
public void Disconnect()
{
try
{
if (m_sqlReader != null && !m_sqlReader.IsClosed)
{
m_sqlReader.Close();
m_dsoConnection.Close();
}
}
catch(SqlException e)
{
throw e;
}
}
protected virtual void PrepareCommand(string sStoredProcedure)
{
try
{
m_dsoCommand.CommandText = sStoredProcedure;
m_dsoCommand.Connection = m_dsoConnection.Connection;
m_dsoCommand.CommandType = CommandType.StoredProcedure;
m_dsoCommand.ClearParameters();
}
catch(Exception exp)
{
throw exp;
}
}
Finally, my custom DSOConnection and DSOCommand classes are defined below:
public class DSOConnection
{
#region fields
private string m_connectionString = null;
private SqlConnection m_connection = null;
#endregion
#region properties
public SqlConnection Connection
{
get
{
return m_connection;
}
}
#endregion
#region methods
#region construction/destruction
public DSOConnection(string connection)
{
m_connectionString = connection;
m_connection = new SqlConnection(m_connectionString);
}
#endregion
#region open/close
public void Open()
{
try
{
if(m_connection.State!=ConnectionState.Open)
{
m_connection.Open();
}
}
catch(Exception e)
{
throw e;
}
}
public void Close()
{
try
{
if(m_connection.State!=ConnectionState.Closed)
{
m_connection.Close();
}
}
catch(SqlException e)
{
throw e;
}
}
#endregion
#endregion
}
public class DSOCommand
{
#region fields
private SqlCommand m_sqlcommand = null;
#endregion
#region constructors
public DSOCommand()
{
m_sqlcommand = new SqlCommand();
}//End of DSOCommand constructor
#endregion
#region Properties
public int CommandTimeOut
{
get
{
return m_sqlcommand.CommandTimeout;
}
set
{
m_sqlcommand.CommandTimeout = value;
}
}
public string CommandText
{
get
{
return m_sqlcommand.CommandText;
}
set
{
m_sqlcommand.CommandText = value;
}
}
public SqlConnection Connection
{
get
{
return m_sqlcommand.Connection;
}
set
{
m_sqlcommand.Connection = value;
}
}
public CommandType CommandType
{
get
{
return m_sqlcommand.CommandType;
}
set
{
m_sqlcommand.CommandType = value;
}
}
public SqlParameterCollection Parameters
{
get
{
return m_sqlcommand.Parameters;
}
}//End of CommandType
#endregion
#region methods
public void ClearParameters()
{
m_sqlcommand.Parameters.Clear();
}//End of ClearParameters
public void AddParameters(string sParameterName, object oValue)
{
if(oValue != null)
{
m_sqlcommand.Parameters.Add(sParameterName,oValue);
}
else
{
m_sqlcommand.Parameters.Add(sParameterName,DBNull.Value);
}
}//End of AddParameters
public void AddParameters(string sParameterName, object oValue, ParameterDirection pdir)
{
SqlParameter p = new SqlParameter(sParameterName, oValue);
p.Direction = pdir;
if(oValue != null)
{
m_sqlcommand.Parameters.Add(p);
}
else
{
p.Value = DBNull.Value;
m_sqlcommand.Parameters.Add(p);
}
}//End of AddParameters
public SqlDataReader ExecuteReader()
{
return m_sqlcommand.ExecuteReader();
}//End of ExecuteReader
public int ExecuteNonQuery()
{
return m_sqlcommand.ExecuteNonQuery();
}//End of ExecuteNonQuery
#endregion
}
I have also included the full text of the error below:
Server Error in '/' Application.
--------------------------------------------------------------------------------
The SqlCommand is currently busy Open, Fetching.
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: System.InvalidOperationException: The SqlCommand is currently busy Open, Fetching.
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:
[InvalidOperationException: The SqlCommand is currently busy Open, Fetching.]
LunchinatorBusinessLayer.Data.Manager.RestaurantManagerDSO.GetAllRestaurantsByGroup(RestaurantCollection col, Int32 groupid) in C:\Documents and Settings\Bob\My Documents\Visual Studio Projects\Lunchinator\LunchinatorBusinessLayer\Data\Manager\RestaurantManagerDSO.cs:266
LunchinatorBusinessLayer.Business.Collection.RestaurantCollection.GetAllRestaurantsByGroup(Int32 groupid) in C:\Documents and Settings\Bob\My Documents\Visual Studio Projects\Lunchinator\LunchinatorBusinessLayer\Business\Collection\RestaurantCollection.cs:67
Lunchinator.Main.Results.SetMostVotes() in c:\inetpub\wwwroot\Lunchinator\Main\Results.aspx.cs:92
Lunchinator.Main.Results.Page_Load(Object sender, EventArgs e) in c:\inetpub\wwwroot\Lunchinator\Main\Results.aspx.cs:68
System.EventHandler.Invoke(Object sender, EventArgs e) +0
System.Web.UI.Control.OnLoad(EventArgs e) +67
System.Web.UI.Control.LoadRecursive() +35
System.Web.UI.Page.ProcessRequestMain() +731
--------------------------------------------------------------------------------
Version Information: Microsoft .NET Framework Version:1.1.4322.573; ASP.NET Version:1.1.4322.573
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