Heads-up: Deprecation and removal of DocumentCreated UKM events
Ramon Cano Aparicio
TLDR: Starting in Chrome Milestone 151, we are stopping the serialization and transmission of DocumentCreated UKM events to the server (link to the change). Instead, use the resolved_urls field in the Source directly.
Why this is changing
Historically, UKM metrics reported from subframes (documents) did not have their parent mainframe navigation URLs directly attached to the subframe source. Analysts had to join these document sources with their parent mainframe navigations on the server side by traversing DocumentCreated events and matching the NavigationSourceId field.
We have now implemented client-side URL resolution. The Chrome client directly resolves the parent mainframe navigation URLs and populates them in the resolved_urls field of the document's `Source` message before sending the report. The resolved_urls field is a repeated string that contains the mainframe navigation URL (including redirects) for the document source. This allows to attribute subframe events directly to the top-level page without performing any server-side joins.
Gradual validation rollouts across Canary, Dev, and Beta channels have confirmed data correctness.
Who is affected
If your team queries UKM data from subframe document sources (e.g., events like WebRTC_AddressHarvesting, Blink.UseCounter from iframes) and relies on manual SQL joins with DocumentCreated to reconstruct the mainframe URL or origin, your existing queries will return empty results for clients on milestone >= 151.
How to migrate
You should update your Plx/BigQuery scripts to use the pre-populated resolved_urls field instead of performing manual joins on DocumentCreated.
For a concrete example of how to update your SQL queries, see this Migration Example Query in the g3doc.
Documentation
The UKM documentation has been updated to reflect this change. For more detailed information and query examples, see:
If you have any questions or need assistance updating your queries, please feel free to ask on YAQS at yaqs/ukm.
Thanks,
Ramon (on behalf of the Chrome Metrics Team)