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Thursday 3 March 2011

Visual Studio's load test and 400 Bad request errors

When trying some load testing with Visual Studio Ultimate edition. My load test received lots of 400 bad request errors. But why?

I had a look at my page that was claiming to be full of errors and it was fine. Even Fiddler reported that there were no 400's being returned from my page.

I took a look more closely at the URL that was returning the 400 and it was not the same as the one I put into the Web Performance test. It had suffixed my URL with %3C%25 - I had a look and this is URL encoding for <%. The 'start writing code' symbol in web forms pages/views.

Workaround to fix this 400 Bad Request %3C%25 problem

I routed about my View and found it could be a problem with the ad calls in the page. They make https ad calls so maybe this is the problem since I heard something about https not being supported properly in load test.

So I stripped the ad call parts out of my View and everything is working fine now.

Obviously this will now affect my page speed so not very accurate. Not impresses given the cost of Visual Studio Ultimate

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  1. Hi,

    Im experiencing a similar error message with a lot of users because of a corrupted cookie (a cookie which has recorded by mistake special character).

    Do you have any idea how I could solve this without asking all my users to clear their caches?

    thanks a lot

  2. On any request chew up their cookies. So if you have a master page you can look for the corrupt cookie in the request. If it is there you can set the expiry of that cookie to a time in the past effectively deleting it for them.

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  4. I took a look more closely at the URL that was returning the 400 and it was not the same as the one I put into the Web Performance test. It had suffixed my URL with %3C%25 - I had a look and this is URL encoding for <%. The 'start writing code' symbol in web forms pages/views. MS-200 dumps

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