YarnClient get app/attempt/container information from RM. If RM doesn't have then queried to ahsClient. When ATSv2 is only enabled, yarnClient will result empty.
YarnClient is used by many users which result in empty information for app/attempt/container report.
Proposal is to have adapter from yarn client so that app/attempt/container reports can be generated from AHSv2Client which does REST API to TimelineReader and get the entity and convert it into app/attempt/container report.