Multiple Simultaneous SQL Connection Timeouts In Multithreaded Windows Service

According to the MSDN Blog post just created today (hooray for Google!):

Microsoft has confirmed that this is a problem in the current release of ADO.NET. This issue will be fixed in ADO.NET version, ships with Visual Studio 2011.

In the meantime, we request to use the following workarounds:

1. Increase the connection string timeout to 150 sec. This will give the first attempt enough time to connect( 150* .08=12 sec)

2. Add MinPool Size=20 in the connection string. This will always maintain a minimum of 20 connections in the pool and there will be less chances of creating new connection, thus reducing the chance of this error.

3. Improve the network performance. Update your NIC drivers to the latest firmware version. We have seen network latency when your NIC card is not compatible with certain Scalable Networking Pack settings. If you are on Windows Vista SP1 or above you may also consider disabling Receive Window Auto-Tuning. If you have NIC teaming enabled, disabling it would be a good option.

The post itself is an interesting read, talking about a TCP/IP connection retry algorithm. And kudos to all the folks who said "hey this looks like it's related to mirroring..."! And note the comment about this being "because of slow response from SQL Server or due to network delays".

UGH!!!

Thanks to everyone who posted. Now we must all ask for a patch to the .NET Framework (or some other ADO.NET patching mechanism), so we don't have to wait for (and buy) Visual Studio 11...

Connection timeout is a different thing than command timeout. Command timeout applies to situation when you have connection established, but due to some internal reasons server cannot return any results within required time. Default command timeout is 30 seconds.http://msdn.microsoft.com/en-us/library/system.data.sqlclient.sqlcommand.commandtimeout.aspx

Try to specify connection timeout in the connection string. Default value is 15 seconds what may be the reason of the issue you see.You can also specify connection timeout in code:http://msdn.microsoft.com/en-us/library/system.data.sqlclient.sqlconnection.connectiontimeout.aspx

I get this every once in a while on this old database server that we have (coming up on 10 years old now). When it does happen though it's because something is hammering that thing with connections/queries constantly. My guess is that you'll find that when it happens the database server is under load (or a high number of connections or something along those lines) Anyway, in my experience if you can optimize the code, optimize the database, getting a beefier database server, etc. all helps. Another thing you can do, which Piotr suggests, is simply up the timeout for the connection. I'd still go through and optimize some stuff though (should help in the long run).