Great! That's what we're looking for as the result of the changes made in T355344: GrowthExperiments: PHP Notice: Undefined index: XXXXXX.

Change #1047108 had a related patch set uploaded (by Michael Große; author: Michael Große):

[mediawiki/extensions/GrowthExperiments@master] Only log error if both registration and last_edit keys are not set

https://gerrit.wikimedia.org/r/1047108

Change #1047108 merged by jenkins-bot:

[mediawiki/extensions/GrowthExperiments@master] Only log error if both registration and last_edit keys are not set

https://gerrit.wikimedia.org/r/1047108

Testing note: check when group 2 is deployed - https://logstash.wikimedia.org/goto/aed67635717e182a88afc0330e118d36

In T366761#9929029, @Etonkovidova wrote:

Testing note: check when group 2 is deployed - https://logstash.wikimedia.org/goto/aed67635717e182a88afc0330e118d36

Yes, we expect there to be many fewer events and them to have a slightly different message: "Registration and last_edit timestamps not found for user ID {userId}"

Note that in rOMWC7de06e315685: CommunityConfiguration: Log info and higher, I decreased the log level for CommunityConfiguration from "everything" to "info and higher". In this particular case, we're logging an error, so it is likely not related to the confusion @Michael mentioned, but noting that regardless, just in case.

In T366761#9933958, @Urbanecm_WMF wrote:

Note that in rOMWC7de06e315685: CommunityConfiguration: Log info and higher, I decreased the log level for CommunityConfiguration from "everything" to "info and higher". In this particular case, we're logging an error, so it is likely not related to the confusion @Michael mentioned, but noting that regardless, just in case.

My understanding was that the logstash Growth team dashboard filter (GE:T366761) excludes the following regardless of the severity level (logstash Growth team dashboard):

{
  "query": {
    "match_phrase": {
      "normalized_message.keyword": "GrowthExperiments\\MentorDashboard\\MenteeOverview\\UncachedMenteeOverviewDataProvider::getFormattedDataForMentor: Registration timestamp not found for user ID {userId}"
    }
  }
}