[HDFS-3862] QJM: don't require a fencer to be configured if shared storage has built-in single-writer semantics

• Type: Sub-task
• Status: Patch Available
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: QuorumJournalManager (HDFS-3077)
• Component/s: ha
• Labels: BB2015-05-TBR
• Assignee: Yi Liu
• Reporter: Todd Lipcon
• Created: 28/Aug/12 20:46
• Updated: 15/Jun/15 06:48

Description

Currently, NN HA requires that the administrator configure a fencing method to ensure that only a single NameNode may write to the shared storage at a time. Some shared edits storage implementations (like QJM) inherently enforce single-writer semantics at the storage level, and thus the user should not be forced to specify one.

We should extend the JournalManager interface so that the HA code can operate without a configured fencer if the JM has such built-in fencing.

Issue Links

• is part of: HDFS-3854 Implement a fence method which should fence the BK shared storage.
• relates to: HDFS-3854 Implement a fence method which should fence the BK shared storage.