can Fiddler run without UI

[Cong Yang]

Hi Everyone,

  Thanks for your time.

  Can Fiddler run without UI?

  Such as in CMD: 

    C:\xxx\fiddler-no-ui.exe -listen 127.0.0.1:8888 -output xxx.saz  ?

  I noticed there's a Fiddler Core. Seems you can develop a no-ui-fiddler your own?

  Basically i would like to open Fiddler all day to capture all HTTP packages. If there's no UI the performance will be good I assume.

Regards,
CY

[EricLaw]

Yes, FiddlerCore is what you would use for this, but Fiddler's UI isn't a significant performance impediment. What overall scenario are you trying to accomplish?

[Cong Yang]

Hi EricLaw,

  Thanks for your reply.

  I'm doing load test lately. I would like to use Fiddler to capture all the HTTP requests I sent. The purpose is when error happens(app error), then I could tell the exact Request which lead to the error by searching in .saz file. The session/user/all-kinds-of-IDs in that Request will help me to trace the error. 

  In load test, 20 concurrent users and run for 15 minutes will generate 20,000 + packages. I noticed Fiddler's memory increased all the time unless I selected all the packages and remove them in the UI. 

  I thought for a while and then realized maybe all I need was a proxy. A proxy which could 1).capture HTTP data  and 2).save it to file periodically and 3).easy to setup. No more no less. I think I may go for Fiddler Core and have a try.

Regards,

CY

  

[Eric Lawrence]

You can configure Fiddler to stream responses and drop the response bodies, which will dramatically decrease the amount of memory used by Fiddler and significantly improve overall performance. See other discussion here: https://fiddlerbook.com/fiddler/perf/PerfMeasure.asp

[Cong Yang]

Great!

[Vadim Kleyzit]

Cong, if you need to search ~20,000 responses to track down performance errors, and your hardware cannot run Fiddler with that many sessions in the grid, then it looks like you would need to write (whether in Fiddler or Fiddlercore) code that saves responses in chunks to saz file(s) while the load test is running.  Here is a workaround. StresStimulus is a load testing Fiddler add-on that can record scenarios and replay them with multiple users. It does not use RAM for captured sessions as it stores them in the embedded SQL CE with 4 GB capacity per test run, so 20 concurrent users would work fine. 

To find your performance errors, after the load test is complete, query sessions from SQL CE to the Fiddler grid http://support.stresstimulus.com/display/doc46/Querying+the+Test+Log   or query SQL CE directly. The free StresStimulus version can run up to 250 concurrent users, but it somewhat limited, so you can use our free trial to find your load testing errors.