Intent to Ship: Attribution Reporting Feature: Prevent Coalescing of Headers

[Akash Nadan]

Contact emails

akash...@google.com, lin...@chromium.org, john...@chromium.org

Explainer

Attribution Reporting with event-level reports

Attribution Reporting API with Aggregatable Reports

Aggregation Service for the Attribution Reporting API

Specification

https://wicg.github.io/attribution-reporting-api/

Blink component

Internals > AttributionReporting

Summary

We are landing the following change to the Attribution Reporting API focused on:

• improving handling of registrations with multiple of the same header

This feature is mainly to address the following edge case.

Currently the API coalesces registration headers if the same header appears multiple times in a response. The individual response values are joined by a "," (comma).

Because the headers contain JSON, this almost always results in an invalid value and therefore responses with multiple of the same header will cause the registration to fail, except in the scenario of the edge case.

Given this potential edge case, and so that the current API behavior persists, this change makes it so that the API explicitly prevents header coalescing. If the same header appears more than once in the response then the registration will be rejected.

Explainer/Spec changes

1. Prevent coalescing for web source/trigger headers 

Risks
Interoperability and Compatibility

This feature is a backwards incompatible change because of the edge case scenario described above. However, as described above, this is not a major concern because currently in all cases except the edge case scenario, which seems very unlikely, the behavior for having multiple of the same header in the response is the same.

              

Will this feature be supported on all six Blink platforms (Windows, Mac, Linux, Chrome OS, Android, and Android WebView)?

The attribution reporting feature will be supported on all platforms with the exception of  Android WebView

Is this feature fully tested by web-platform-tests?

Yes

Estimated milestones

This feature is anticipated to ship as part of Chrome 126. 

Link to entry on the Chrome Platform Status

https://chromestatus.com/feature/5204901830590464

Links to previous Intent discussions

Previous I2S: 

Intent to Ship: Attribution Reporting API

Intent to Ship: Attribution Reporting features M117

Intent to Ship: Attribution Reporting features M118

Intent to Ship: Attribution Reporting features M119

Intent to Ship: Attribution Reporting features M120

Intent to Ship: Attribution Reporting features M121

Intent to Ship: Attribution Reporting features M123

Intent to Ship: Attribution Reporting features M124

Intern to Ship: Attribution Reporting features M125

[Domenic Denicola]

This feature seems problematic from a web architecture point of view. I have added a comment on https://github.com/WICG/attribution-reporting-api/issues/1202 .

Getting full review from parties like the TAG or other browsers probably does not make sense for this kind of a small change to the Attribution Reporting Feature (which has had its own previous reviews). But, there are several experts in the Fetch and HTTP space who I would like to give a chance to comment on this, as I am especially worried about the precedent it sets. I have tagged them in the above issue.

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[Anthony Garant]

After getting feedback, we decided to no longer pursue this feature. We appreciate the input.

Thanks,

Anthony

To view this discussion on the web visit https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAM0wra__h3rBBSf_KFv4u92sC_LX%3DDVT4YKLdPdYvvwREHvsFA%40mail.gmail.com.

[Domenic Denicola]

Thanks for being flexible on this in response to feedback!