[HBASE-12733] High volume of "Couldn't find oldest seqNum" warnings if bypassing WAL

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Won't Fix
• Labels: beginner
• Assignee: Unassigned
• Reporter: Andrew Kyle Purtell
• Created: 20/Dec/14 01:06
• Updated: 17/Jun/22 18:45
• Resolved: 26/May/16 22:29

Description

When ingesting with the WAL bypassed, the RegionServer will log the following at every flush:

2014-12-19 16:58:24,630 WARN  [MemStoreFlusher.0] wal.FSHLog: Couldn't find oldest seqNum for the region we are about to flush: [86fc8c1374ebc29cc4a39a78966d48e0]

The WAL won't find a seqnum for the region until the first edit which does not bypass the WAL. That might not be for hundreds or thousands of flushes. This shouldn't be at WARN level since ingest with WAL bypass is legal if a bit unusual. It's concerning that the FSHLog code that emits that warning has a TODO above suggesting the warning should instead be an assertion.