How to simulate a DB connection timeout - sql-server

Question

We are in a situation where some of our connections are timing out (possibly), we need to handle the code in certain way if the connection to SQL timesout, I know that command timeouts can easily be simulated by using WAITFORDELAY but how would you simulate a connection timeout ?

Answer 1

I just managed to simulate a connection time out
1st execute the following query on your sql server (I did it in ssms)
ALTER DATABASE my_Test_DB SET SINGLE_USER;
Fired up the following code from Visual Studio
namespace TimeOut_Test_Project_ASP
{
public partial class _Default : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
string cs = "Data Source=ServerName;Initial Catalog=my_Test_DB; Integrated Security=SSPI;Connect Timeout=3";
using (SqlConnection con = new SqlConnection(cs))
{
SqlCommand cmd = new SqlCommand("SELECT * FROM dbo.TableName", con);
con.Open();
GridView1.DataSource = cmd.ExecuteReader();
GridView1.DataBind();
}
}
}
}
Error Stack
Server Error in '/' Application.
The wait operation timed out
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.ComponentModel.Win32Exception: The wait operation timed out
Stack Trace:
[Win32Exception (0x80004005): The wait operation timed out]
[SqlException (0x80131904): Connection Timeout Expired. The timeout period elapsed during the post-login phase. The connection could have timed out while waiting for server to complete the login process and respond; Or it could have timed out while attempting to create multiple active connections. The duration spent while attempting to connect to this server was - [Pre-Login] initialization=309; handshake=1; [Login] initialization=0; authentication=1; [Post-Login] complete=2002; ]
System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction) +5340655
System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose) +244
System.Data.SqlClient.TdsParserStateObject.ReadSniError(TdsParserStateObject stateObj, UInt32 error) +601
System.Data.SqlClient.TdsParserStateObject.ReadSniSyncOverAsync() +256
System.Data.SqlClient.TdsParserStateObject.TryReadNetworkPacket() +39
System.Data.SqlClient.TdsParserStateObject.TryPrepareBuffer() +64
System.Data.SqlClient.TdsParserStateObject.TryReadByte(Byte& value) +86
System.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady) +222
System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj) +69
System.Data.SqlClient.SqlInternalConnectionTds.CompleteLogin(Boolean enlistOK) +30
System.Data.SqlClient.SqlInternalConnectionTds.AttemptOneLogin(ServerInfo serverInfo, String newPassword, SecureString newSecurePassword, Boolean ignoreSniOpenTimeout, TimeoutTimer timeout, Boolean withFailover) +317
System.Data.SqlClient.SqlInternalConnectionTds.LoginNoFailover(ServerInfo serverInfo, String newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance, SqlConnectionString connectionOptions, SqlCredential credential, TimeoutTimer timeout) +891
System.Data.SqlClient.SqlInternalConnectionTds.OpenLoginEnlist(TimeoutTimer timeout, SqlConnectionString connectionOptions, SqlCredential credential, String newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance) +307
System.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdentity identity, SqlConnectionString connectionOptions, SqlCredential credential, Object providerInfo, String newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance, SqlConnectionString userConnectionOptions, SessionData reconnectSessionData) +518
System.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOptions options, DbConnectionPoolKey poolKey, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningConnection, DbConnectionOptions userOptions) +278
System.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(DbConnectionPool pool, DbConnection owningObject, DbConnectionOptions options, DbConnectionPoolKey poolKey, DbConnectionOptions userOptions) +38
System.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection) +732
System.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection) +85
System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, UInt32 waitForMultipleObjectsTimeout, Boolean allowCreate, Boolean onlyOneCheckConnection, DbConnectionOptions userOptions, DbConnectionInternal& connection) +1057
System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal& connection) +78
System.Data.ProviderBase.DbConnectionFactory.TryGetConnection(DbConnection owningConnection, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal oldConnection, DbConnectionInternal& connection) +196
System.Data.ProviderBase.DbConnectionInternal.TryOpenConnectionInternal(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions) +146
System.Data.ProviderBase.DbConnectionClosed.TryOpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions) +16
System.Data.SqlClient.SqlConnection.TryOpenInner(TaskCompletionSource`1 retry) +94
System.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource`1 retry) +110
System.Data.SqlClient.SqlConnection.Open() +96
First_Project_ASP._Default.Page_Load(Object sender, EventArgs e) in D:\c# Projects\First Project ASP\First Project ASP\Default.aspx.cs:22
System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +51
System.Web.UI.Control.OnLoad(EventArgs e) +92
System.Web.UI.Control.LoadRecursive() +54
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +772
Set back your database to multi-use mode
ALTER DATABASE [my_Test_DB] SET MULTI_USER;

Answer 2

After seeing this comment, I had the idea to try connecting to the wrong host, and it works.
Keep the username, DB, etc. as normal, but change the "host" parameter to be a valid URL/IP that you have control of, but such that the username and password won't work.
The connection will time out.
This way, you don't have to ALTER your database in any way, so it's really nice.
It might also work to use other incorrect connection parameters, like the database name.

Answer 3

You can also try setting the timeout to one second and see if it then throws the timeout exception. Note that 1 is as low a value as you can set. Add to your connection string "Connection Timeout=1;". Note that this is a CONNECTION timeout, not a query timeout which is a different thing altogether and not set in the connection string. Note that this may or may not work to actually simulate it if the connection is made in under 1 second.
I have also tried just disconnecting the network cable from my dev machine just before trying to make the connection.