(Sorry if this is a really long question, it said to be specific)
The company I work for has a number of sites, which have been running for some time with no problems. The applications are a mix of ASP.NET 2.0, 3.5, and 4.0, all using an ADO.NET to connect to a SQL Server Standard instance (on the same webserver) all being hosted with IIS7.
The problem began when we moved to an upgraded webserver. We made every effort to set up the server, db instance and IIS with the exact same settings (except for the different machine name, and the fact that we had upgraded from SQLExpress to Standard), and as far as we could tell, we did. Both servers are running Windows Server 2008 R2 (all current updates applied), and received a default install.
The problem is very apparent when starting up one of these applications. When you reach the login page of our application, the page itself loads extremely fast. This is true even when you load the page from a new machine that could not possibly have the page cached, with IIS caching disabled. The problem is actually visible when you enter your login information and click the login button. Because of the (not great)design of our databases, the login process must access a number of databases, theoretically up to 150 separate DBs, but in practice usually 2. The problem occurs even when only 2 databases (the minimum) are opened. Not a great design, but we have to live with it for now.
When trying to initially open a connection to the database, the entire process stops for about 20 seconds every time, regardless of whether you are connecting to 2 dbs or 40. I have run a .NET profiler (jetbrains dottrace) against the process, and the only information I could take from it was that one or all of the calls to sqlconnection.open() was accounting for 90% of the time. This only happens on first-use of the application, but the problem is compounded by the fact that IIS seems to disregard the recycling settings we have set for it, and recycles the application after a few minutes of idle, causing the problem to occur again.
I also tried to use the SQL Server profiler to see which database operations were the cause of the slowdown, but because of all the other DB activity, (and the fact that I had to do this on our production server, because the problem doesnt occur in our test environments) I couldn’t pin down the exact operation that was causing the stoppage. I will try coming in late at night and shutting down the production sites to run the SQL profiler, but I might not be able to do this right away.
In the course of researching the problem, I have tried a couple solutions
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Thinking it might be a name resolution problem, I tried modifiying both the hosts file on the webserver as well as giving the connectionstrings an IP address instead of the servername to resolve, with no difference. I have heard of the LLMNR protocol causing problems like this, but I think trying to connect by IP or resolving with the hosts file should have eliminated that possibility, tho i admit I never tried actually turning off LLMNR.
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I have increased the idle timeouts, recycling intervals etc in IIS, but this doesn’t even seem to be respected, much less solving the problem. This leads me to believe there is a setting overriding the IIS application settings on the machine.
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multiple other code fixes, none of which made any difference. Is a SqlServer setting causing the problem?
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other stuff that i forgot by now.
Any ideas, experience or whatevers would be greatly appreciated in helping me solve this problem!
I would advise using a non-tcp connection if you are still running the SQL instance on the local machine. SQL Server supports several protocols, tcp, named pipes, and shared memory are the more common.
Named Pipes
Shared Memory
Personally I prefer the Shared Memory. Remember you need to enable these protocols, and to avoid configuration mistakes I suggest you disable all you are not using.
see http://msdn.microsoft.com/en-us/library/ms187892.aspx
IIS Reset
In IIS7 there are two ways to configure the idle-timeout. Both begin by clicking on the “Application Pools” section and right-clicking the appropriate app domain. If you click the “Recycling…” option there is one setting. The other is in “Advanced Settings…” under the section for “Process Model” you will find “Idle Time-out (minutes)” which set to zero disables the process timeout. This later option is the one that works for us.
If I were you I’d solve this problem first as restarting the appdomain and/or worker process is always painful even if you don’t have a 20 second lag.