I have a web application that occasionally will throw this error….
Exception message: Timeout expired.
The timeout period elapsed prior to
completion of the operation or the
server is not responding.
When I does I am unable to connect to SQL server, even through management studio, it’s says the server timed out and cannot connect.
As soon as I reset iis, it comes back instantly. So this obviously means it’s something in my code that’s causing this. I have an MVC site that uses Linq to SQL and SQL cache dependency with service broker enabled.
I have used the using statement thoroughly throughout the code, so im sure it’s not leaky connections. Reading through the server logs makes things more confusing as there are so many information and warning events, im not a sys admin so it’s hard to know what’s going on.
It begins with me getting an ASP.net 4.xxxxx Event ID 1309 Exception message: Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding. error
I think I got round it last time on my previous server by restating IIS when ever this error popped up, this is something I don’t want to resort to on this new server.
So my question is, what steps can I take to try and reduce but ideally eliminate this timeout error ?
Any help is most appreciated
Truegilly
This type of problem usually boils down to one of two things. Either you are not disposing of your connections properly or you have a number of heavy queries that are completely taking over your database server.
If you don't dispose of the connections properly then IIS will happily keep them around until garbage collection runs and/or they timeout. If you have a very lightly trafficked site then you won't see the problem.
However, once traffic reaches the point where the number of connections hanging around exceeds the number of times you are trying to make a connection to the database server.. well, you are going to start seeing one of a couple possible errors. Timeout expired is one. The exact error is going to depend on which part is falling over: the connection pool, the sql server itself, etc.
The fix you commented on is a temporary solution. As your traffic continues to increase (good problem to have) then other areas of your code are going to cause the issue to come up again.
Related
We are using SQL Server 2012 Enterprise edition.
Normally we get hardly any blocked processes, but last weekend we experienced very unusual situation. Within 2 hours we got more "blocked process" alerts than we did in the last year together. There were a few hundred alerts within this time. Then suddenly without any interference from anyone everything went back to norm and we didn't get any blocked processes ever since. I want to prevent this situation from occurring again.
I am well aware how to find what can be causing blocking at present, but I have very little idea how to find what caused the block in the past, which is currently resolved.
I checked error logs in SQL Server Management Studio, but there is nothing there under the date when blocking occurred. There is also nothing unusual in the Windows event viewer. Where else should I check?
Could you please help?
From what you describe, I'm not too sure you will actually find the cause of the previously blocking processes if you did not actively setup tracing i.e. have your blocked process threshold set and configured with an alert to provide said trace information. The situation you described is interesting and definitely worth monitoring.
Here is an article on blocked process threshold configuration in SQL Server and a link through to Alerts configuration.
Hope this helps
We are having multi server and multi DB instances in EC2. In one of the Server we have the Main DB(Master DB), but in other servers we have only the Transaction DB's. We are using SQL linked server to connect everything.
Initially there was no problem with my infrastructure. But now as the data load increased, am often getting Time Out expired error even for an normal select query.
Its not for all the processes. If there are 500 processes running in a particular server, in that at-least 200 processes are throwing this Time out expired error.
Recently, I moved all my servers into VPC.
Note:
All my queries will be running only from Master DB because only master DB knows what transaction DB is connected to respective transaction requests. All EC2 instances are in the same region.
Is there a solution for my problem ( time out error exception ). Kindly help me with your suggestions. This is really turning out into an critical business affecting issue.
Error Msg:
Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding.
Since it worked fine before and started to fail with as load increased, sounds like you are running out or resources (mostly hardware). There are two things to do:
1) Buy more hardware;
2) Tunning your queries to do more work with less (hardware).
The first thing is (maybe) cheaper. To tuning your DB it ill take a lot of time for learning and test out whatever you learn.
I suggest you to get the hard way and try to optimize your queries/isolation level/schema etc.
We are having some strange performance issues and I was hoping somebody may be able to point us in the right direction. Our scenario is an ASP.NET MVC C# website using EF4 POCO in IIS 7 (highly specced servers, dedicated just for this application).
Obviously it's slow on application_startup which is to be expected, but once that has loaded you can navigate the site and everything is nice and snappy 0.5ms page loads (we are using Mini-Profiler). Now if you stop using the site for say 5 - 10 minutes (we have the app pool recycle set to 2 hours and we are logging so we know that it hasn't been recycled) then the first page load is ridiculously slow, 10 - 15 seconds, but then you can navigate around again without issue (0.5ms).
This is not SQL queries that are slow as all queries seem to work fine after the first page hit even if they haven't been run yet so not caching anywhere either.
We have done a huge amount of testing and I can't figure this out. The main thing I have tried so far is to Pre generate EF views but this has not helped.
It seems after looking at Sql Server Profiler after 5 minutes give or take 30 seconds with no activity in Sql Server Profiler and no site interaction a couple of "Audit Logout" entries appear for the application and as soon as that happens it then seems to take 10 - 15 seconds to refresh the application. Is there an idle timeout on Sql Server?
This should work if you use the below in your connection string:
server=MyServer;database=MyDatabase;Min Pool Size=1;Max Pool Size=100
It will force your connection pool to always maintain at least one connection. I must say I don't recommend this (persistant connection) but it will solve your problem.
Are you using LMHOSTS file? We had same issue. LMHOSTS file cache expires after 10 minutes by default. After system has been sitting idle for 10 minutes the host would use Broadcast message before reloading the LMHOSTS file causing the delay.
It seems after looking at Sql Server Profiler after 5 minutes give or
take 30 seconds with no activity in Sql Server Profiler and no site
interaction a couple of "Audit Logout" entries appear for the
application and as soon as that happens it then seems to take 10 - 15
seconds to refresh the application. Is there an idle timeout on Sql
Server?
This is telling me that the issue most likely lies with your SQL server and/or the connection to it rather than with your application. SQL server uses connection pooling and SQL will scavange these pools every so often and clean them up. The delay you appear to be experiencing is when your connection pools have been cleaned up (the audit logouts) and you are having to establish a new connection. I would talk/work with your SQL database people.
For testing, do you have access to a local/dev copy of the database not running on the same SQL server as your production app? If not, try and get one setup and see if you suffer from the same issues.
I would run "SQL Server Profiler" against SQL Server and capture a new trace while reproducing the problem by accessing the site after being idle 5-10 mins. After that look at the trace. Specifically, look for entries in which ApplicationName starts with "EntityFramework...". This will tell you what is EF doing at that moment. There could be some issue with custom caching on top of EF, or some session state that is expiring (check sessionState timeout in web.config)
Since it is the first run (per app?) that is slow, you may be experiencing the compilation of the EDMX or the LINQ into SQL.
Possible solutions:
Use precompiled views and precompiled queries (may require a lot of refactoring).
http://msdn.microsoft.com/en-us/library/bb896240.aspx
http://blogs.msdn.com/b/dmcat/archive/2010/04/21/isolating-performance-with-precompiled-pre-generated-views-in-the-entity-framework-4.aspx
http://msdn.microsoft.com/en-us/library/bb896297.aspx
http://msdn.microsoft.com/en-us/magazine/ee336024.aspx
Dry run all your queries on app start (prior to first request is received).
You can run queries with a fake input (e.g. non existing zero keys) on a default connection string (can be to an empty database). Just make sure you don't throw exceptions (use SingleOrDefault() instead of Single() and handle null results and 0-length list results on .ToList()).
Create a simple webpage that accesses the SQL Server with a trivial query like "Select getDate()" or some other cheap query. Then use an external service like Pingdom or other monitor to hit that page every 30 seconds or so. That should keep the connections warm.
Try to overwrite your timeout in the web.config like in this example:
Data Source=mydatabase;Initial Catalog=Match;Persist Security Info=True
;User ID=User;Password=password;Connection Timeout=120
If it works, this is not a solution..just a work around.
In our case the application was hosted in Azure App Service Plan and was having similar problem. Turned out to be a problem of not configuring virtual network. See the question/answer here - EF Core 3.1.14 Recurring Cold Start
I have come across an issue that seems to be somehow connected to a web server configuration, and resulting in queries randomly taking a long time to execute. The application is created using old plain Classic ASP and ADODB Connection is used.
The scenario goes as follows:
there is a single connection opened in a script at the beginning of processing each HTTP request
this connection is used to execute a query against a SQL Server, that resides on a separate box. conn.Execute is used. Connection is NOT closed afterwards
there are usually a few to a few dozens of conn.Execute in a single ASP page
All has been working well until recently, when some of the conn.Execute started to take much longer to execute, totally on random.
the difference is e.g. 15ms normal execution time vs. 2000ms long execution time
on the SQL Server side, Profiler does not show longer query execution times, so there must be something blocking the conn.Execute request
When a proper practice of closing a connection after each conn.Execute has been implemented, the issue goes away. However, as I have stated before, all has been working flawlessly until recently. This web app is a fairly large one and rewriting it to close and reopen connections properly will take some time. And I need a short-term solution.
My guess is that it could have something to do with the connection pool size, however this is not ADO.NET, therefore I am not sure, whether a connection pool issue should be taken into the consideration at all. On the SQL Server side, there is no limit on the number of concurrent connections to the server.
I need some hints. Brainstorming possible ideas.
Could be related to delays resolving the hostname in the connection string via DNS - have you tried putting an IP address in the connection string instead of the hostname?
My method executes lots of asynchronous SQL requests and I constantly get connection timeout exceptions. What else can I do except increasing the connection timeout value and proper indexing? I mean with the database part, not with the code part. Can't change the code part. Besides, the application is running fine on different servers, but only I experience those timeout exceptions on my pc and local MS SQL Server 2008 R2 database (which is also on the same PC). So I think this is clearly a performance issue since the connection timeout is already set to 3 minutes. Maybe there is something I can change on the server? Maybe there is a number of simultanious requests constraint? Each of my requests needs clearly less that 3 minutes, but there are about 26 000 of them running asynchroniously, and only I experience those problems on my local PC and local DB.
I've run the process monitor and I see that at the time when my code starts the SQL Server eventually consumes 200 MB of RAM and takes up about a half of CPU processing time. But I still have 1 GB of RAM free, so this is not a memory problem.
I think the number of connection can be the cause. Make sure you close the connection properly or try to reduce the amount of them. You can also use pipes, which will overcome the limitations of usual connections.