Silverlight app can't connect to ArcGIS server intermittently

[KevinSesock]

I spent some time last week with ESRI support on this issue, and we're all stumped. Thought I would put it to the forums to see if anyone else has experienced this issue.

Most likely an issue with our ArcGIS server, I'm hoping someone can help us diagnose.

We're having an intermittent issue, only with our custom Silverlight application, where it will generate an error with our query tasks being used to populate some drop-down boxes or with our Sublayer list. The error is inevitably related to an inability to hit our ArcGIS server and query or pull down the appropriate data from REST.

The error seems to occur for a client machine that has not accessed our Silverlight app in several days, but I fail to understand how this could be a client cache issue. The only way we are able to force the application to generate the error is by restarting IIS, which seems to cause the REST cache to go away for a few seconds, but just clearing the REST cache doesn't do it. The .xap loads just fine, it's just that if it hasn't loaded in a while, it can't connect to the ArcGIS server on REST, and then, once you refresh, it works just fine.

Here is what we have done:

1. Changed our REST cache settings
2. Used Fiddler to no avail (no 404s, the most we have are 304s).
3. Checked ArcGIS server logs (nothing) on verbose (still nothing), Event Viewer for both IIS (lots more of nothing) and all the other places (guess what... nothing).

We're stumped. So far, there seems to be no reason why this is occurring. It is extremely intermittent. Anyone have any ideas on where to start?

[DaveTimmins]

Hi Kevin,

a few things to check first.

Does it happen from multiple client machines?
Have you tried using a different way of consuming the endpoint (JS api etc.) and is the behaviour the same?
Does it happen with different services on the same AGS or only one? Or does it happen with different services on different AGS machines?

Secondly, it sounds like you are only seeing this behaviour when querying data. I've had issues with services not initialising correctly due to a timeout(usually due to AGS starting a new SOC instance). Can you verify that there are SOC processes running and available. In order to get around our issue I basically check the layer InitializationFailed event and force a re-initialise by changing the url (add or remove a '/' to the end as the url needs to change otherwise it will use the client cache) up to a specified maximum number of retries. Could be worth looking into for your issue.

Let me know how you get on.

regards,
Dave Timmins
@davetimmins

[DarinaTchountcheva]

Hi Kevin,

If nothing else works, try the script in this thread, it works for me (I scheduled it to run every 15 minutes):

http://forums.esri.com/Thread.asp?c=158&f=2276&t=228654&mc=137#812067

Good Luck!

[dotMorten_esri]

If you keep Fiddler running at all times, try and track the request/responses when the server fails. It might give you some clue to what happened.