I know this is a hot topic on StackOverflow, but do bear with me.
We have a Silverlight 3 application talking to a WCF service. Every now and then, calls to the WCF service return a NotFound exception.
I've read pretty much every post on SO and Google on this subject but I can't figure out what's going wrong. Here are some of my findings:
The exception happens on random calls and at random moments. Sometimes a method will work for 50 times and suddently it bugs out. I have a feeling it's related to a timeout, since it's most reproducable if I let the application idle for a while before invoking a call, but this is not always the case - sometimes the one of the first calls in the application fails.
We use the SilverlightFaultBehavior to convert the HTTP error code to 200 and we have plenty of instances where throwing an exception on the serverside actually bubbles up to the client side, so I can confirm this should be working as expected.
Fiddler shows nothing special at the moment the exception occurs. I don't even see the call in question. This worries me, but it might mean that the exception is a result of a call that happened minutes ago and timed out?
Service Trace Viewer shows nothing.
I attach Visual Studio to to Silverlight project and to the WCF services project, set debugging to break on all exceptions (thrown or handled) and it doesn't break (except in Silverlight to tell me about the NotFound problem). This causes me to think that maybe the NotFound is not in response to an exception on the WCF service side?
I really have no idea where to go from here. Any help at all, any pointers or ideas of things to try are welcome.
Here are some thoughts for the points you mentioned:
1) The exception happens on random calls and at random moments - Make sure the data being sent as a return value of method is valid. I had a case when sending an object with some empty properties caused a failure in serialization. I found this out using IIS logs/ Service Trace Logs.
2) So, did you find anything useful?
3) I don't think fiddler can help with this kind of an error.
4) Are you sure about this? Did you set up Trace Logs correctly?
5) You won't find any exceptions that can help you here. The actual exception (when you see 'Not Found' error) is raised while wrapping the message/data from server side or unwrapping message/data on client side.
So, to summarize make sure the data is in correct format (may seem to be correct for you but not WCF, just play with it for a while with different values) and verify the Trace Logging again.
What is a binding of the service? Where is it hosted: IIS or VS Deployment server?
I have seen this problem recently, something was wrong with IIS. It couldn't even open *.svc files.
So here is a plan of activities:
Try to open svc file using http address like http://localhost/MyApp/MyService.svc
If it opens, write a console application and test the service.
If it works, write a silverlight simple application.
I hope this will help.
I fixed this by adding
minFreeMemoryPercentageToActivateService="1"
to Web.config. By default it is
minFreeMemoryPercentageToActivateService="5"
which sometime causes this error.
Related
I have recently changed to use custom Go runtime on GAE, and noticed many errors like this from logs:
internal.flushLog: Flush RPC: Call error 3: invalid security ticket: 6c8027dc99b3ed3e
internal.flushLog: Flush RPC: Canceled: (timeout)
The server is still running well, but I have no idea about that error, as well as why it happens.
I'm using a custom Go runtime by using Dockerfile, and App Engine Release is 1.9.37.
Any help to clarify the error would be highly appreciated. Thanks.
This is a known issue with the Go runtime on App Engine Flexible. It tends to happen when a line is logged right before the end of a request/response.
What happens is that when the line is logged it is actually put in a list of log lines to be batched together and sent to the application server as an RPC at periodic intervals. The security ticket is canceled at the end of a request/response which sometimes can happen before the log lines have been flushed. It's harmless, except that you may lose a log line or two. :\
We're actively working on fixing it.
We are using Episerver and ImageVault and it has worked fine for a long time. Until recently when showing albums to public users stopped working for no apparent reason.
No code changes in our project or change to the surrounding server environment.
An exception is thrown when the IVFileList control databinds. The exception that is thrown is "the trust relationship between the primary domain and the trusted domain failed".
I have debugged the code and come to the conclusion that the reason for the exception is actually because episerver tries to find a user called "Anonymous" with the WindowsMemberShipProvider. I have included a simplified stack trace below (excluded several calls for readability). I starts of with the DataBind call which leads to a call to episervers multiplexprovider to find the user "Anonymous" this in turn leads to a call to the method TranslateToSids that throws the exception.
System.Security.Principal.NTAccount.TranslateToSids(...)
EPiServer.Security.MultiplexingMembershipProvider.FindMembershipUser("Anonymous")
ImageStoreNET.Developer.WebControls.IVFileListData.DataBind()
I found a workaround for this problem by creating an local account in the webserver and named it "Anonymous". And now it all works again! The TranslateToSids method no longer throws the exception and the album pictures are visible.
Does anyone have a theory why this account suddenly is needed? We never had one before as we can recall. Although the workaround works, it feels like a ugly solution to create a local account. It should be a more correct way of solving this. Any suggestions?
We have built a website based on the design of the Kigg project on CodePlex:
http://kigg.codeplex.com/releases/view/28200
Basically, the code uses the repository pattern, with a repository implementation based on Linq-To-Sql. Full source code can be found at the link above.
The site has been running for some time now and just about a year ago we started to get errors like:
There is already an open DataReader associated with this Command which must be closed first.
ExecuteNonQuery requires an open and available Connection. The connection's current state is closed.
These are the closest error examples I can find based on my memory. These errors started to occur when the site traffic started to pick up. After banging my head against the wall, I figured out assumed that the problem is inherit within Linq-To-Sql and how we are using the same connection to call multiple commands in a single web request.
Evenually, I discovered MARS (Multiple Active Result Sets) and added that to the data context's connection string and like magic, all of my errors went away.
Now, fast forward about 1 year and the site traffic has increased tremendously. Every week or so, I will get an error in SQL Server that reads:
A severe error occurred on the current command. The results, if any, should be discarded
Immediately after this error, I receive hundreds to thousands of InvalidCastException errors in the error logs. Basically, this error shows up for each and every call to the Linq-To-Sql data context. Only after I restart the web server do these errors clear up.
I read a post on the Micosoft Support site that descrived my problem (minus the InvalidCastException errors) and stating the solution is that if I'm going to use MARS that I should also use Asncronous Processing=True. I tried this, but it did not solve my problem either.
Not really sure where to go from here. Hopefully someone here has seen and solved this problem before.
I have the same issue. Once the errors start, I have to restart the IIS Application Pool to fix.
I have not been able to reproduce the bug in dev despite trying many different scenarios involving multi-threading, leaving connections open, etc etc.
One possible lead I do have is that amongst the errors in the server Event Log is an OutOfMemoryException for the Application Pool. Perhaps this is the underlying cause of the spurious SQL Datareader errors (a memory leak elsewhere). Although again I haven't been able to reproduce this in dev.
Obviously if you are using a 64 bit OS then this is probably not the cause in your case.
So after much refactoring and re-architecting, we figured out that problem all along is MARS (Multiple Active Result Sets) itself. Not sure why or what happens exactly but MARS somehow gets result sets mixed up and doesn't recover until the web app is restarted.
We removed MARS and the errors stopped.
If I remember correctly, we added MARS to solve the problem where a connection/command was already closed using LinqToSql and we tried to access an object graph that hadn't been loaded. Without MARS, we'd get an error. But when we added MARS, it seemed to not care about it. This is really a great example of us not really understanding what the heck we were doing and we learned some valuable (and expensive) lessons from this.
Hope this helps others who have experienced this.
Thanks to all how have contributed their comments and answers.
I understand you figured out the solution..
Following is not a direct solution to the problem; but it is good for others to take a look at
What does "A severe error occurred on the current command. The results, if any, should be discarded." SQL Azure error mean?
http://social.msdn.microsoft.com/Forums/en-US/bbe589f8-e0eb-402e-b374-dbc74a089afc/severe-error-in-current-command-during-datareaderread
I'm having huge difficulty debugging database operations from Silverlight RIA. This is understandable, I suppose, since database operations are abstracted by about 3 layers of services and ORM and stuff, but is there any way I can see what the database is telling me regarding the issue? I'm able to find an EntityConflict object which doesn't offer much information.
The only field which seems to indicate any problem is "IsDeleted" property equal to true, however this property is not well documented at MSDN and I cannot even be sure that having it be true is an issue.
I've attempted to use fiddler, however no errors are reaching that, I've attached to the application's unhadled exception, but that points me back to EntityConflict, which I am recovering through handling SubmittedChanges event and accessing the args. I've even enabled WCF tracing to attempt to recover some information but, of course, nothing there either.
Did you inspect SubmitOperation.Error after the submit operation failed? It should contain the error information you seek. More information on error handling can be found here: Link
The issue was a known issue, at least a few years ago, where INSTEAD OF INSERT doesn't return Scope_identity for a column inserted by this method. EF uses this value to verify that an insert was completed. When it fails, you get a deletion conflict. This is, apparently, a known issue with the SQL Server EF provider, however I have been unable to confirm that it's been resolved.
I'm developing a silverlight application that consumes a webservice. Calls to this webservice are made Asynchronously. But when an exception occurs during a procedure of the async call, I get an error on the completed event but i lost my original exceptions information. Independent of what the original exception was, I always get "The remote server returned an error: NotFound" back, with stack that points to "external" code.
Any advice?
When the service throws an exception it's translated to a 40(x) HTTP response that gets handled by the browser before the Silverlight plugin can handle it. To avoid this, wrap your WCF calls in a try/catch block and send exception data back to the client through an HTTP response that can be handled by Silverlight, such as 200. Here's a terrific implementation of this strategy on codeproject:
http://www.codeproject.com/KB/silverlight/SilverlightExceptions.aspx
This happens with any exception in your SL to WCF, sometimes you can find the innerexception with Fiddler2 in the transfered data or you might see the HTTP error code which can give you a hint , other times it's harder to find. This is my big request item for SL 4.0, better WCF debugging.
http://www.fiddler2.com
Follow James Cadd's advice above. Getting more informative error messages will certainly help and, unfortunately, you can't rely on the debugger to generate them for you.
Even if you're not a big fan of unit testing, this is a place where it's more than worthwhile. Constructing a set of tests that will purposefully send your webservice bad data and making sure that you get back informative errors will help set you up to figure out why it's not working with the Silverlight app. Writing these kinds of tests takes a different way of thinking, but it will give you a lot of confidence in your code if you know that you've tried to break the webservice in every possible way and it always gives you back something you can use to trace the problem.