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Duplicate requests with FiddlerCore

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Shab
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Shab asked on 13 Feb 2014, 06:12 PM
We are using FiddlerCore (v. 4.4.5.6) to capture traffic from our test suite that makes calls against the product servers (behind a VIP). And we are finding ghost requests hitting our servers - that is:
1. The Fiddler log from the client (saved using FiddlerCore) shows a single call.
2. The server logs from product servers shows that two different servers handled this same request.
The request has a unique  randomly generated secret token, so we know that it is the exact same request. So somehow a duplicate request is being fired that does not show up in the FiddlerCore trace. We discounted for now a potential issue with the F5-VIP for now.

This issue repros intermittently - so we can't really validate by just disabling FiddlerCore integration.

Is it possible for us to introduce such a scenario if we have a bug in how we integrate with the FiddlerCore session callbacks?

Or is there a possible bug in the version of FiddlerCore that we are using that might result in this behavior?

Appreciate any pointers,
Thanks!

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EricLaw
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answered on 13 Feb 2014, 08:03 PM
Do you see the same behavior if you use Fiddler? Do you have a network capture (e.g. Wireshark)?

If your server is using KeepAlive connections AND Fiddler reuses a connection AND the server fails to accept a request on that reused connection (e.g. by closing the connection) then Fiddler will resend the request on another (or new) connection. In practice, servers rarely accept requests without replying to them, but if there were a bug in the server, it's conceivable that this could occur.
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Shab
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answered on 14 Feb 2014, 10:32 PM
I am working on getting a repro with NetMon tracing enabled. Will update this thread once I get more data.
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Russell
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answered on 27 Feb 2014, 06:04 PM
Hi Eric, Shab and I have collected NetMon and Fiddler tracing for this situation.  Can you please contact me offline so that I can share this information with you?
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EricLaw
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answered on 27 Feb 2014, 11:59 PM
I'm not sure how I'd contact you offline. If you'd like to email me, Help > Send Feedback in Fiddler, or mail fiddler@telerik.
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Russell
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answered on 28 Feb 2014, 12:46 AM
Thanks I'll contact you at that email.
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EricLaw
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Shab
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Russell
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