[HBASE-6856] Document the LeaseException thrown in scanner next

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.92.0
• Fix Version/s: 0.95.0
• Component/s: documentation
• Labels: LeaseException
• Hadoop Flags: Reviewed
• Assignee: Daniel Iancu
• Reporter: Daniel Iancu
• Created: 21/Sep/12 14:56
• Updated: 23/Sep/13 18:31
• Resolved: 21/Sep/12 18:32

Description

In some situations clients that fetch data from a RS get a LeaseException instead of the usual ScannerTimeoutException/UnknownScannerException.

This particular case should be documented in the HBase guide.

Some key points

• the source of exception is: org.apache.hadoop.hbase.regionserver.Leases.removeLease(Leases.java:230)

• it happens in the context of a slow/freezing RS#next

• it can be prevented by having hbase.rpc.timeout > hbase.regionserver.lease.period

Harsh J investigated the issue and has some conclusions, see

http://mail-archives.apache.org/mod_mbox/hbase-user/201209.mbox/%3CCAOcnVr3R-LqtKhFsk8Bhrm-YW2i9O6J6Fhjz2h7q6_sxvwd2yw%40mail.gmail.com%3E