I have a website using Microsoft SQL 2008 server over local network. Sometimes, SQL server machine is rebooted, and so the website fails to connect to the database. If the machine is up and running, it will respond fast. If it's down, there is no need to wait for 15 seconds. 3 seconds are ok.
I want to display apologizes on the website when the database is not reachable, and want to do it fast. But setting Connection Timeout=3 in connection string seems having no effect. The page spends 22 seconds to wait before throwing SqlException on SqlConnection.Open();.
What's wrong with it? May it be a hidden configuration which overrides the timeout?
Currently, my connection string is
Data Source=...;
Initial Catalog=...;
Integrated Security=True;
Connection Timeout=3
If I set it to ...;ConnectionTimeout=3 (without space),
System.ArgumentException: Keyword not supported: 'connectiontimeout'.
is thrown (strange, MSDN documentation indicates that we can use both strings).
There is a timeout before the networking hardware reports connection timeout to the network drivers, which in turn notifies the programs waiting for network IO. You can verify transport layer timeouts via telnet servername 1433 (assuming your sql server is listening on port 1433).
But 3 seconds is way too short for a process to initialize the network APIs (assuming your web app is in its own application pool), send request and wait for the hardware to timeout. Updating BIOS/firmware/driver probably won't reduce the response time that much.
It would be better to carry out the connection asynchronously. i do not suggest using EndInvoke to end the asynchronous call as unlucky users may still need to wait 3 full seconds to see any response when the database is down. Maybe an Ajax call is better. If you have a lot of users constantly hitting your web site, you may want to cache the result of connectivity checking and update it in a manner meaningful to your users.
The following blog post assisted me in solving this problem:
http://improve.dk/controlling-sqlconnection-timeouts/
ConnectionTimeout without space is the property name when accessing via code, not for the connection string.
Not sure if this is of use, but when I hit this issue in the past, it was because I also needed to set SqlCommand.CommandTimeout. What happened for me is the connection was opened successfully, then DB server went down, then my next command did not timeout as quickly as I expected based on the Connection Timeout, and this was due to the CommandTimeout needing to be set as well.
Related
In c# namedpipes have the horrible characteristics to get into loops of full cpu load during connecting (waiting for server), and in my case, also when the server is closing leaving the client alone. And this is my question: Can the client detect a server shutdown (server disconnect) by events?
Currently I run a timer, testing the connection every 2nd second. This works as I can close the connection in the client and dispose the namedpipeclientstram what stops the high cpu load. However it means in worst case there is very high cpu load for up to 2 seconds.
However to avoid any high cpu load at all I´m searching an kind of event system to detect one-sided connection shutdown of the server in the client. Is there any? I have not found anything so far.
It would be also ok to force the client stream not to seek reconnection when
server is closing (at least it looks like this is happening as it resembles very much the cpu state during a wait for the server)
The connection is bidirectional and async.
One more question about named pipes: When the server is up and ready, would it be ok to try to connect as client with a specified timeout of 0? Does this specify at least one trial, immediatly returning if server is not up?
Or does the timeout has be at least as high as network delays or server response times are ?
Thx for help
Stefan
So this issue is NOT one of having too many connection strings or connection strings not being disposed of properly. ASP.NET Sql Server stored session has been working great for months with decent traffic on the website, now I am getting many Unable to connect to SQL Server session database - The wait operation timed out exceptions. There is plenty of memory available for the database, the database has plenty of memory allocated. There is just a few users on the website when it is throwing errors.
I have two blade servers sitting right next to each other and very low traffic to the website so I shouldn't need to increase the connection timeout from the default 15 seconds.
I am using Windows Authentication and I can connect via SSMS and query my ASPSession database that is being used as the persistence layer for ASP.SESSION no problem.
I just have no were to go on this error currently.
Looks like the issue an I/O error with the raid on my database server. Had to swap out a hard drive and all seems well.
I had the same issue, and I didn't know why, because I setted the timeout for 300 seconds(5minutes) at app.config, elsewhise I didn't notice when I was using sqlCommand the timeout of connection was 300 seconds, but for the sqlCommand was 30 seconds, so I setted the sqlCommand.ConnectionTimeout = 300 (was 30) and solved my problem.
Also I read in somewhere about using WITH NOLOCK, that solves for someones, this will speed up your sql, but I suggest to read about at Microsoft because this is not something you should use with you don't understand the concept.
We have a 3-tier application with a C# client, a C# WCF web service layer, and a SQL Server database. The web service connects to the database with ADO.NET. All of our C# code is using the .NET Framework 2.0.
Recently, a customer performed a stress test on our application. During the test, the web server generated a lot of errors like the following:
Could not connect to database for connection string '...'. Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding.
I am aware there are ways to catch connection errors when the connection pool is full and try acquiring a connection outside of the connection pool. We also found several queries that needed to be tuned, but they dot not explain web server connection timeouts.
We're trying to figure out why the web server was timing out connecting to the database. I have setup the web server to enable all of the ADO.NET performance counters. However, I don't see anything related to the times required to connect or connection timeouts or the like. Ideally, we would be able to graph the connection times in perfmon next to the other ADO.NET counters.
Is there a way to monitor the ADO.NET performance in acquiring connections?
I imagine we could create our own "average connection open time" performance counter by timing attempts to open connections, but I'd rather use something that already exists.
You can use perfmon to get this information. You'll need to attach to the User Connections monitor under SQL Server: General Statistics. Here is the blog post I grabbed that from. This will let you know at what point in time connections are being left open.
You will then need to correlate that with application tasks (i.e. stuff you're doing in the application when you see them continually climb).
Once you've done that you're going to want to get those connections inside a using statement if you don't already:
using (SqlConnection cn = new SqlConnection("some connection string"))
{
cn.Open();
...
}
by doing this you won't need to issue a Close and you won't have to worry about them getting disposed of properly.
In short, the performance counter should help you track down the code in the application that's causing the issue, but it won't be down to the line per say, it will take a bit more effort even from there.
I have a Timer in a C# app (Win7 64). Every 20 min the timer callback gets some data via HTTP. It works well. But if my PC goes to sleep for a few hours, then wakes up, I get an HTTP error saying "can't find the server". The server is running at all times, so it's not the real issue. I suspect the real reason is that as the timer callback misses its "time slot" during the sleep period, it becomes "overdue" and is executed instantly right after the wake-up, without waiting for the PC to re-establish the Internet connection. I can fix the problem by adding a Thread.Sleep(5000) at the beginning of the callback, but it's a bit of a kludge (establishing Internet connection might take longer). My questions:
After a wake-up from sleep mode, does Win indeed need a few seconds to re-establish Internet connection? My connection is DSL, "always online".
Is there a C# system call which would wait until Win establishes the Internet connection (or time out if this doesn't happen within, say, 20 secs)?
EDIT: Just found this: Check Net connection in C#. Not as simple as I hoped, it takes a sequence of checks: any LAN connection, DNS lookup (outside the LAN), ping a server (check a particular server).
1) Yes
2) You may check various connection attributes via WMI for example. See: http://msdn.microsoft.com/en-us/library/windows/desktop/aa394595%28v=vs.85%29.aspx
and
http://msdn.microsoft.com/en-us/library/windows/desktop/aa394216%28v=vs.85%29.aspx
to make sure you have a connection before attempting a query.
I don't think you should bother with WMI and such.
If you cannot access the network, set the timer to fire in a minuts instead of 20. You alrsady have a waiting mechanism in place, reusing it will not seem kludgy.
I have a chat site (http://www.pitput.com) that connects user via socket connections.
I have in the client side a flash object that opens a connection to a port in my server.
In the server i have a service that is listening to that port in an async matter.
All is working fine except when i talk to someone after an unknown period of time(about couple of minutes) the server is closing my connection and i get an error in the server :
" A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond".
I dont know how exactly the tcp socket works. does it checking for "live" connection every couple of seconds? how does it decide when to close the connection? Im pretty sure that the close operation is not coming from the client side.
Thanks.
Sounds like the server is handling the connection but not responding. This is the point where I usually pull out WireShark to find out what's going on.
TCP/IP does have an option for checking for live connections; it's called "keepalive." Keepalives are hardly ever used. They're not enabled by default. They can be enabled on a system-wide basis by tweaking the Registry, but IIRC the lowest timeout is 1 hour. They can also be enabled on a single socket (with a timeout in minutes), but you would know if your application does that.
If you are using a web service and your client is connecting to an HTTP/HTTPS port, then it may be getting closed by the HTTP server (which usually close their connections after a couple minutes of idle time). It is also possible that an intermediate router may be closing it on your behalf after an amount of idle time (this is not default behavior, but corporate routers are sometimes configured with such "helpful" settings).
If you are using a Win32 service, then it does in fact sound like the client side is dropping the connection or losing their network (e.g., moving outside the range of a wireless router). In the latter case, it's possible that the client remains oblivious to the fact that the connection has been closed (this situation is called "half-open"); the server sees the close but the client thinks the connection is still there.
Is this an ASP web service hosted with some company? If so, the server generally recycles apps every 10 to 20 minutes. You cannot have a web service running indefinitely, unless it's your own server (I believe).