I have a c# app that exports data from the database to the user's Exchange Calendar, using Microsoft.Exchange.WebServices (15.0.0.0). My app is DotNet 4.5.2 and I use Visual Studio 2013.
The app has been working fine for a year, and even now works 95% of the time. The app runs constantly on machine that I am logged into and monitor. This is a low volume process, perhaps 50 items get exported per day at most.
Every couple of days, the program will give this error:
"The request failed. Unable to connect to the remote server"
when the app is attempting to create an EWS connection to the server.
It will do this for maybe 10-20 items. So I shut it down, run it again, and it works perfectly fine on all the records that failed before.
This is my first EWS app, but I've been programming 30+ years and do have somewhat little knowledge of internet based apps.
Any helpful information or suggestions would be greatly appreciated!
Thank you kind people!
The internet often works, but should never be considered reliable. Anything using it should handle errors, and retry if desired. The classic approach is Exponential backoff. Its possible something nasty is going on, like your ISP swapped your IP address, or just intermittent failure. I don't know anything EWS specific, but there may also be sources of flaky issues there as well.
Related
I have an blazor server-side app deployed on average 100 site which generally works pretty well.
But for very few site, end-users complain about micro disconnection/reconnection on the app (they see the components-reconnect-modal few seconds).
I logged some information on the OnConnectionUpAsync and OnConnectionDownAsync of the CircuitHandler to see whats happen, and effectively i notice some log showing a lot of time client disconnected for one, two or three seconds. But i don't have the reason
There is an average of maybe 50 and 100 end user connected at the same time at the app on this site.
I really don't know how to start to investigate this case. This client have a server well dimensionnate, with recent windows server, the configuration is OK.
I don't have specific configuration or parameters on the app
I would suspect the problem is on the network of my client (so not specific on my app, like shutdown of the network for 3 second), but The client assure me is network works very well and he don't have any problems with his others apps.
Have you any idea what i can do to have more information on this problem ?
do you know some tools which can test the network and show potentials problems ?
thanks in advance
This is my first Stack Overflow question so apologies if this isn't great...
I'm sure this is something either super simple I am missing or something very complex that I've gotten myself into, but I am using ClickOnce for the first time to create an automated updater for a company application I developed.
The application itself was originally written in VB but I have translated it into C#. We use this to automate a database of assets, which changes very frequently. I have been tasked to allow it to complete automated updates to keep from confusing some of the techs with uninstall/reinstalling the application weekly.
I volunteered to make an FTP server using a personal server machine I use at home. Normally this machine would be used for local networking but I've wanted to create an FTP server for some time (this is my first FTP server too).
So I went on my way, set the publish location for the build to ftp://[IP.ADDRESS]:21/Folder/Subfolder and the Installation folder URL to http://[IP.ADDRESS]:21/Folder/Subfolder
Long story short, when I try to test an update (changing only the assembly version), I am an error:
System.Deployment.Application.DeploymentDownloadException: Downloading http://[IP.ADDRESS]:21/Folder/Subfolder/applciation.application did not succeed ---> System.Net.WebException: The server committed a protocol violation.
I did some research and tried adding an SSL certificate and changed the update path to https://[IP.ADDRESS]:21/Folder/Subfolder/ then tested that. This time around, I get this error:
System.Deployment.Application.DeploymentDownloadException: Downloading http://[IP.ADDRESS]:21/Folder/Subfolder/applciation.application did not succeed ---> System.Net.WebException: The underlying connection was closed: An unexpected error occurred on a send. --> System.IO.IOException: The handshake failed due to an unexpected format.
I cannot tell if this is progress or if I moved backwards here LOL. I've been jumping back and forth and going to many threads to try to figure out where this is going wrong. I'm also having a pretty tricky time finding out if this is an error with how I've set up ClickOnce or if this is an error in how I have set up FTP with IIS.
Apologies if this is not enough information, I can provide more if necessary. Also apologies if this is too much information! Any help or guidance is appreciated!
I'm guessing you're working for a small company and infrastructure/resources are at a premium. With that in mind I'll offer some suggestions:
Does your company have a network shared drive? I don't like ClickOnce, but I have deployed it to network shares in the past with success. This has the benefit of you not needing to deal with security.
Have you considered migrating this to a web application? Web development seemed really daunting when I was a native app developer, but with Blazor and ASP.NET Core it's become a lot more accessible. This would completely get rid of the need for updating the application.
Consider an alternative deployment route. ClickOnce is not incredibly well supported.
I'd be remiss if I didn't throw a red flag on security. FTP is a very old protocol and is basically insecure by design. Hosting it on your home server means that you're transmitting the app over the public internet... What would happen if someone outside your company installed the application?
It is not a specific problem because I have more than one experience that fiddler save my app.
A recent example:
I had an excel addin app write in C#. In the app I had a httpclient to connect to my server through ssl. And I ignored the certification in my code explicitly.
The app always worked well(I mean the connection part), but one day in a QA environment, it failed in no causes. The connection seemed to be blocked for long long time.
Coincidentally, we opened the Fiddler and tried to grab some http. Then everything worked fine.
(Fiddler may do something in the middle)
Then after closing Fiddler, we cannot recreate the problem because all things went back to fine again.
(Fiddler change something permanently!)
Here are some clues:
We use the normal C# http clients System.Net.Http .
Our server is ssl (https, but we must ignore the cert)
The app was good in the same environment at frist.
The lastest change is about the localization, and the test enviroment changed the windows local and language.
We are under a company network, using a proxy in the example above.
The failure is not the whole connection module, but a specific request.(In our case, a request that post two small xml files including excel itself)
Please give us some hint and guess, so we can feel better on this mystical problem.
How long is a "long long time" exactly?
Fiddler does not make any persistent changes to the system; if you start and stop it, the system is returned to the prior configuration. I suppose it's remotely possible that if some configuration setting were corrupt before Fiddler ran, that corruption wouldn't be replicated after Fiddler attempted to reapply it, but we don't know of any such "corrections."
This article describes some of the things folks find unexpected in terms of Fiddler "magically" fixing things while it runs.
(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
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.
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.
multiple other code fixes, none of which made any difference. Is a SqlServer setting causing the problem?
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
Data Source=np:computer\instance
Shared Memory
Data Source=lpc:computer\instance
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.
Some ideas:
from the web server, can you ping the db server and get a "normal"
response, or are you seeing a similar delay?
if you're seeing a delay, run a tracert to see if you can nail down where the slowness is occurring
try using a tool like QueryExpress (http://www.albahari.com/queryexpress.aspx) which doesn't require an install to run. You can download this EXE and run it from your web server. See if you can connect to your db using this and run queries in a normal fashion.
Try something like SysInternals' TcpView (http://technet.microsoft.com/en-us/sysinternals/bb897437) to take a look at your open connections and see what activity is happening on your server and how much data is being sent to and received from your db server.
Just some initial thoughts on where I'd start to look based upon your problem description. I hope this helps. Good luck with things!
With IIS not respecting recycling settings: did restarting IIS/rebooting change the behavior?
Whenever I debug my application (ASP.NET Web Application converted to Web Role), I am able to get to the login page. I go ahead and sign in, debug through that and it seems to work fine, but as soon as it takes me to the landing page after login, DevFC.exe stops working with the error:
An unhandled exception ('System.Net.Sockets.SocketException') occurred in DevFC.exe [8072].
Now, I've searched for the issue and have seen something about DevFC.exe crashing due to VMWare Workstation that listens on the same port (12000) and HTC Sync that also listens on that port. I have neither of those applications on my machine, so I am lost here. Using TCPView (from Sysinternals), I find no other application using that port.
The one thing I do notice is that [System Process] goes crazy creating connections to localhost:12000 once DevFC.exe gets started.
Anyone have some insight on this?
This might sound ridiculous but restarting your machine might solve the issue. If that doesn't work, try your project on a different machine. If the project works then there is an issue with your primary machine try uninstalling then reinstalling the Azure SDK. If the devFabric still crashes on the secondary machine then it's something related to your project.
You might want to take a look at the logs created in the DevFC folder here: %localappdata%\dftemp\DevFCLogs (C:\Users\[user]\AppData\Local\dftmp\DevFCLogs). This will hopefully shed light on the actual error (which in my case, was a conflict on port 12001. Ran netstat -ab afterwards and found it was vmware-hostd.exe. This is a service included with VMWare Workstation 8. I know you said you don't have that, but you may have some other conflicting software).
See this thread as well for more detail.
http://social.msdn.microsoft.com/Forums/en-US/windowsazuredevelopment/thread/7e205afd-4b9a-4387-8e10-99e4b8f27788