Strange intermittent SQL connection error, fix on reboot, returned after 3-5 days (ASP.NET)

Question

For some reason, every 3-5 days our web application loses its ability to open a connection with db with the following error, it is strange that all we need to do is reload the container (this is VPS) and it restores to normal functionality. Then after a few days or so, this happens again. Has anyone had such a problem? I noticed a lot of anonymous logs in the security log in the middle of the night from our AD server, which is strange, as well as some of the IP addresses in Amsterdam. I’m not sure how to say what exactly they mean, or if it is connected or not.

Server Error in '/ntsb' Application. A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server) 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.Data.SqlClient.SqlException: A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server) Source Error: Line 11: Line 12: Line 13: dbConnection.Open() Line 14: Line 15: Source File: C:\Inetpub\wwwroot\includes\connection.ascx Line: 13 Stack Trace: [SqlException (0x80131904): A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server)] System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection) +248 System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj) +245 System.Data.SqlClient.TdsParser.Connect(ServerInfo serverInfo, SqlInternalConnectionTds connHandler, Boolean ignoreSniOpenTimeout, Int64 timerExpire, Boolean encrypt, Boolean trustServerCert, Boolean integratedSecurity, SqlConnection owningObject) +475 System.Data.SqlClient.SqlInternalConnectionTds.AttemptOneLogin(ServerInfo serverInfo, String newPassword, Boolean ignoreSniOpenTimeout, Int64 timerExpire, SqlConnection owningObject) +260 System.Data.SqlClient.SqlInternalConnectionTds.LoginNoFailover(String host, String newPassword, Boolean redirectedUserInstance, SqlConnection owningObject, SqlConnectionString connectionOptions, Int64 timerStart) +2445449 System.Data.SqlClient.SqlInternalConnectionTds.OpenLoginEnlist(SqlConnection owningObject, SqlConnectionString connectionOptions, String newPassword, Boolean redirectedUserInstance) +2445144 System.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdentity identity, SqlConnectionString connectionOptions, Object providerInfo, String newPassword, SqlConnection owningObject, Boolean redirectedUserInstance) +354 System.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOptions options, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningConnection) +703 System.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(DbConnection owningConnection, DbConnectionPool pool, DbConnectionOptions options) +54 System.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnection owningObject) +2414696 System.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection owningObject) +92 System.Data.ProviderBase.DbConnectionPool.GetConnection(DbConnection owningObject) +1657 System.Data.ProviderBase.DbConnectionFactory.GetConnection(DbConnection owningConnection) +84 System.Data.ProviderBase.DbConnectionClosed.OpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory) +1645687 System.Data.SqlClient.SqlConnection.Open() +258 ASP.includes_connection_ascx.getConnection() in C:\Inetpub\wwwroot\includes\connection.ascx:13 ASP.default_aspx.Page_Load(Object sender, EventArgs e) in C:\Inetpub\wwwroot\Default.aspx:16 System.Web.Util.CalliHelper.EventArgFunctionCaller(IntPtr fp, Object o, Object t, EventArgs e) +25 System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +42 System.Web.UI.Control.OnLoad(EventArgs e) +132 System.Web.UI.Control.LoadRecursive() +66 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2428 Version Information: Microsoft .NET Framework Version:2.0.50727.3053; ASP.NET Version:2.0.50727.3053 

Answer 1

The number of allowed connections to the sql server is a fixed resource. It seems that you have a code somewhere that does not close it correctly, and after some time you cannot open new ones.

Answer 2

We recently encountered a similar problem in our production environment, and after many rounds of "debugdiag" ging and analysis of dumps, we came to the conclusion that the reason for this is the fragmentation of a large array of a large object. Ref http://msdn.microsoft.com/en-us/magazine/cc534993.aspx . In short, your application may have run out of memory and did not have enough contiguos space to open connections. You can use VMMap http://technet.microsoft.com/en-us/sysinternals/dd535533 to determine the available free space. Do you recycle your AppPools regularly? AppPool recycle crashes the application and frees up any help memory, therefore, fixes any problems associated with it.

Answer 3

Have you tried to collect basic information with perfmon and profiler (trace) to find out how many connections are made, memory statistics and other interesting things?

Answer 4

"I noticed a lot of anonymous logs in the security log in the middle of the night from our AD server, which is strange, as well as some of the IP addresses in Amsterdam."

It sounds as if you might have someone trying to get into your system, and maybe those connections that don't close. I like the suggestion to use perfmon and profiler to see the problem.