Corrupting Map, all tiles are jumbled up

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Fabien
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Fabien asked on 14 Jan 2022, 10:43 AM

Hi,

We using the Telerik Map component for a production use. The used provider is OpenStreetMap.
A customer contacted us with an issue. He was using Sophos proxy/OpenVPN at his company but he is the only one in the company to have the problem.
No explicit rules are set on the Sophos admin console.
But the problem is not here, explainations:

I took remote control of his PC to see the problem. After a few tries, the tiles on the map were still displayed out of order like a jigsaw puzzle.
I installed Fiddler 4 to see what was going on and if it was a bad request or something else.
My big surprise was that by using Fiddler, the map problem disappeared! Reversely, when quitting the application, the map problem reappeared.

I guess using Fiddler allows the map to time out and allows the map to display correctly.
My customer using a racing machine. All its configuration can be seen in the attachment files.

Do you have a workaround for that?

Thanks in advance for your reply.

Best regards.

Fabien.

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Stenly
Telerik team
answered on 19 Jan 2022, 09:08 AM

Hello Fabien,

We have multiple reports on such issues with scrambled tiles but we have never reproduced it locally. Usually, this originates from tile caching and we advise our clients to first test if stopping the caching fixes the map - set IsTileCachingEnabled to False on the MapProvider. If this is the issue, then you can try different caching options.

In addition, could you please explore the following thread where similar issues are discussed and some clients report that certain antivirus software might break the caching:

Map tiles are jumbled up, corrupting map in UI for WPF | Telerik Forums

With that said, I hope the provided information is of help to you. Let me know if you need any further assistance.

Regards,
Stenly
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Fabien
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commented on 20 Jan 2022, 07:57 AM

Hi,

Thanks for your reply.
Unfortunatly, that does not help. The cache was set to false and different RequestCacheLevel was tried to figure it out. No effect.

I read the thread you gave me. The only thing I see, it's a threading problem or a layout problem which can corrupts the request.

My customer will receive an another PC which will be more powerful. He will try it on that PC. I will update that thread.

Thanks.

Best regards,

Fabien.

Stenly
Telerik team
commented on 24 Jan 2022, 01:35 PM

I am sorry to hear that setting these properties up wasn't of any help to you. Apart from the threading and layout problems you referenced, I noticed the following comment, from the forum thread that I have provided, which seems identical to the one you described:

"As far as I am aware we got a temporary fix for this by requesting our network admin to configure the proxy so that requests to OSM and Bing map servers are allowed straight through. It appears that without this the Sophos proxy caches tiles, and it seemed like the cache behavior was incorrect."

With that said, would it be possible for you to change the proxy settings at your end as well and see whether this helps?

Fabien
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commented on 09 Feb 2022, 07:59 AM

Hi,

The answer of my customer:

I read with interest the answer of the editor.
I did a final test. I still have "big squares" that appears. On my Sophos Appliance, I analyzed the traffic from my computer to the outside. I have no blocking alerts while using the app.

From an Internet browser on my computer, OpenStreetMap and Bing map work.

In view of the elements transmitted by the editor, I do not have anything to do at the level of the Sophos Appliance (Do they use particular UDP/TCP ports, to which IP/URL recipient, what are the APIs they use) or is it something else?

At the SOPHOS Appliance level, for my workstation, I have disabled all the Firewall rules and the problem persists.

Any other tests that we can do?

Thanks.

Stenly
Telerik team
commented on 14 Feb 2022, 07:56 AM

Hello Fabien,

May I ask if you could set the RequestCacheLevel property, of the OpenStreetMapProvider instance, to NoCacheNoStore, while keeping the IsTileCachingEnabled property to False, and let me know how it goes?

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