Hello @SimL    YARN Timeline Server v2 Reader uses HBase for Storage. The Log & HBCK Report shows the Table "prod.timelineservice.entity" has Regions in OPENING State, which would naturally cause any Client accessing the Table report RetriesExhaustedWithDetailsException.   A Region is typically stuck in OPENING State, if there is any issues with WALEditReplay or any other reason, which would be clear from the RegionServer Logs where the Region is being opened. Unless the RegionServer Logs are available, any Comment is unlikely to be an accurate assessment of the issue your team is facing. Would recommend checking the RegionServer Logs wherein the Regions are in OPENING State & based on the cause, plan accordingly.    - Smarak ... View more