Suppress transaction IDs

[bretg]

In contrast to the buyer-initiated effort to add imp.ext.tid in #2381, we now need to partly walk that change back.

Requirements

1. The Prebid Publisher committee has determined that neither Prebid.is nor Prebid Server should send source.tid or imp.ext.tid to bidders by default.
2. It should be possible for accounts to opt-in to sending these values to bidders.
3. Analytics adapters should be able to receive these tid values.
4. We may need to add $.id into the list at some point.

Implementation

We discussed in committee two options for building this feature:

• a new set of account-level config
• add a new activity to the "activity infrastructure" being built out as part of PBS GPP phase 3 #2591

After discussing these options, a new 'transmitTid' activity has been added to section 3.3.4 of https://docs.google.com/document/d/1dRxFUFmhh2jGanzGZvfkK_6jtHPpHXWD7Qsi6KEugeE/edit#

To support the desire for suppression to be default, the PBJS team would like to send us a behavioral flag:

ext.prebid.createtids: false

If this flag is present and false, the code that enforces the transmitTid activity when preparing the bidder requests should remove / not add source.tid and imp.ext.tid.

Note that we do not intend to implement a general activity override on the ORTB request due to complexities in determining priority of request-parameters vs the activity config. So this is considered a one-off feature. If at some point we decide that request-level control of activities is a general requirement, there will be a separate set of requirements.

[SyntaxNode]

Item 4 was discussed in Backlog Grooming. Per recommendation of the Committee, I created a new issue #2794 to discuss how to handle the request id.

[bretg]

Spoke with the Prebid.js team. They're going to name this activity transmitTid. They pointed out that the "any false" rule makes the idea of supporting an inverse activity problematic.

Would like to discuss in the next committee meeting

[bretg]

Discussed in PBS committee and agreed on transmitTid

[bretg]

Flipped back to Needs Requirements until we can discuss the newly proposed request-level flag ext.prebid.createtids

[bretg]

Discussed in committee.

There will be two ways of controlling the passing of imp.ext.tid:

1. the request carries ext.prebid.createtids:false. If this flag is false, then PBS won't create tids. The default for ext.prebid.createtids is true.
2. the account-level config disallows the transmitTids activity. If this is disallowed, then PBS will remove imp.ext.tid from bidder, analytics, and modules. This behavior can be controlled through Activity Control conditions.

The relevant code in Prebid.js is https://github.com/prebid/Prebid.js/blob/e1acefe45a251c49eae3b538b71eea973bf5d860/modules/prebidServerBidAdapter/ortbConverter.js#L78

[bretg]

To clarify how this integrates with #2381...

1. If request parameter ext.prebid.createtids=false, then the transmitTid activity is overridden to disallowed.
2. If request parameter ext.prebid.createtids=true, then the transmitTid activity is overridden to allowed.
3. ext.prebid.createtids does not have a default, meaning transmitTid is utilized.

There are two specific tasks tied to the transmitTid activity

$.source.tid

if source.tid is not set and the transmitTid activity is allowed:
   set source.tid to a random UUID  // existing behavior
// new behavior
if host config generate-storedrequest-bidrequest-id config is true and the transmitTid activity is allowed
    if the storedrequest is from AMP or from a top-level stored request (ext.prebid.storedrequest), then replace any existing $.source.tid with a random value
if $.source.tid contains "{{UUID}}", replace that macro with a random value

$.imp[].ext.tid

for each imp:
   if imp[n].ext.tid is not set and the transmitTid activity is allowed:
       set imp[n].ext.tid to a randomly generated UUID
   if host config generate-storedrequest-bidrequest-id config is true and the transmitTid activity is allowed
       if the storedrequest is from AMP or from a top-level stored request (ext.prebid.storedrequest), then replace any existing $.imp[n].ext.tid with a random value
  if $.imp[n].ext.tid contains "{{UUID}}", replace that macro with a random value

Note: there are no changes for .id and .imp[].id in this issue, but see #2794

[bretg]

Done with PBS-Java 2.2