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RE: [ResourceTiming] startTime definition

From: Jatinder Mann <jmann@microsoft.com>
Date: Tue, 15 May 2012 18:40:22 +0000
To: Boris Zbarsky <bzbarsky@MIT.EDU>, "public-web-perf@w3.org" <public-web-perf@w3.org>
Message-ID: <AE5FFD9402CD4F4785E812F2C9929D6504EF997C@SN2PRD0310MB383.namprd03.prod.outlook.com>
> I have to ask: why is the intended behavior different depending on the exact redirects involved, 
> anyway?  It seems really weird that if I fetch A which redirects to B then startTime on the result 
> will depend on the exact redirect chain from A to B...
>
> -Boris

We want startTime to be the time of queuing a resource for fetching. 

For privacy reasons, if any of the redirects are not from the same origin and the Timing-Allow-Origin rules are not met, we zero out the redirectStart or redirectEnd times, see the attribute definitions here: http://www.w3c-test.org/webperf/specs/ResourceTiming/#dom-performanceresourcetiming-redirectstart.  In this particular scenario, if the startTime continues to be the time of queuing the fetch of the resource that initiates the redirect process, we in effect will have circumvented the privacy restrictions we placed on redirectStart and redirectEnd times.

For that reason, this text expectedly calls out that for redirects that are same-origin or have met the Timing-Allow-Origin rules, startTime will be the time of queuing the fetch of the resource that initiates the redirect process and when any of the redirects are not same-origin and the Timing-Allow-Origin rules have not been met, startTime will be the time of queuing the fetch of the final resource from the redirect process.

Thanks,
Jatinder
Received on Tuesday, 15 May 2012 18:42:01 UTC

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