Allow Bidder to Override Callback Type in /setuid

[AlexBVolcy]

Addressing a piece of this larger issue: #2173

This PR will allow a bidder to force override its callback to be either iframe or redirect, based on a configuration they can now set in their .yaml formatOverride

Use Case from issue: client creates iframe, the cookie-family's iframe drops image. The usersync type is 'iframe'. The default f=b response works, but returns blank into an img, which may not be ideal in some scenarios. Use a format override to set f=i instead of the default f=b.

[hhhjort]

I don't understand the use case here. From the linked issue, I could not find a clear explanation of what this is supposed to be implementing. What you have done seems to force the /setuid endpoint to respond with an empty gif or an empty html response reguardless what the URL indicates should be the response. This seems broken, as the call will expect one type based on the 'f' parameter it is using, and will lead to a browser error if the wrong type is returned.

The only place I can make a forced type make sense is in the /cookie_sync endpoint, where you can force the sync type to be a certain type, so the downstream caller can format the call with the appropriate type of tag despite what the cookie_sync sync endpoint is told is preferred.

Possibly I suppose to allow the bidder's sync code to specify the wrong value if the "f=" parameter, but then fix it on the PBS side, but I think the proper response here is to tell the bidder to fix their sync code rather than putting a hack in PBS to correct the sync type.

What am I missing here?

[AlexBVolcy]

@hhhjort I think I’m the one probably missing something. Scott and I spoke a few weeks ago about various aspects of the linked issue that needed to be handled, and there’s one line in the linked issue referencing what this PR is trying to address: “Allow a bidder to override it's setuid callback type from either iframe or image”

This specific part of the issue we didn’t dive into great detail on, but I figured overriding a setuid callback type would refer to overriding what is being returned by getResponseFormat() within /setuid. However, the concerns that you bring up make sense. @SyntaxNode, do you have any more info for how I should be approaching about this override?

In the meantime, I'm going to investigate the Java code to see if/how they handle address this piece of the issue.

[SyntaxNode]

What am I missing here?

The linked issue identifies the use case as:

Client creates iframe, the cookie-family's iframe drops image. The usersync type is 'iframe'. The default f=b response works, but returns blank into an <img>, which may not be ideal in some scenarios. Use the format override to set f=i.

I'm not clear on the situation where a sync iframe would return an image. @bretg is better versed with the lifecycle and edge cases of iframe syncs.

[bretg]

@AlexBVolcy - please help me understand the use case here.

allow a bidder to force override its callback to be either iframe or redirect

At this point, I don't think this is correct or desirable.

Bidders should be able to supply both iframe and pixel syncs, and they can express a preference, but it doesn't make sense to me that a bidder should be able to force it -- this is a page/publisher decision, not a bidder decision.

[SyntaxNode]

Bidders should be able to supply both iframe and pixel syncs, and they can express a preference, but it doesn't make sense to me that a bidder should be able to force it -- this is a page/publisher decision, not a bidder decision.

@bretg This PR is adding the "formatOverride" feature introduced in PBS-Java to PBS-Go. The questions are for it's use case. There doesn't appear to be any bidder using this today. Could you please when a bidder would want to set "formatOverride"?

[bretg]

Right, ok, this is the use case from the issue

2. client creates iframe, the cookie-family's iframe drops image. The usersync type is 'iframe'. The
default f=b response works, but returns blank into an img, which may not be ideal in some
scenarios. Use a format override to set f=i instead of the default f=b.

So formatOverride is a way for iframe-sync URLs to be built with /setuid calls containing f=i instead of the default f=b

[SyntaxNode]

@bretg Gothcha. Why would iframe sync URLs need to return f=i instead of f=b?

[bretg]

There was a scenario where someone was emitting an iframe, and in that iframe they were dropping a pixel back to PBS rather than using AJAX

[hhhjort]

There was a scenario where someone was emitting an iframe, and in that iframe they were dropping a pixel back to PBS rather than using AJAX

In the code delivered by the iframe, why don't they just hardcode the pixel to have f=i in the URL, rather than allowing it to be f=b in the iframe body, but then correct it when it hits PBS to be a pixel? It would seem that any bidder that uses this override feature would lock themselves into always using empty images or blank text on the setuid call for all their sync cases. It would seem to be better to just always use f= in the setuid URL rather than disregarding that setting and assuming that the bidder always knows better than the HTML that the call is coming from.

[bretg]

why don't they just hardcode the pixel to have f=i in the URL

Because PBS generates the redirect URL.

[AlexBVolcy]

Just to keep this PR updated: After speaking with @SyntaxNode, this PR is correctly addressing the feature that we want implemented.

I'm just addressing some small comments, and this will be ready for review soon.

[SyntaxNode]

This is no longer used after the refactor and can be deleted.

[SyntaxNode]

Nitpick: Since these are moved out of the sync package, consider renaming to SyncResponseFormatIFrame and SyncResponseFormatRedirect to add back that context.