[HDFS-3867] QJM: Support rolling restart of JNs

• Type: Sub-task
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: QuorumJournalManager (HDFS-3077)
• Component/s: ha
• Target Version/s: QuorumJournalManager (HDFS-3077)
• Assignee: Todd Lipcon
• Reporter: Todd Lipcon
• Created: 29/Aug/12 22:35
• Updated: 06/Sep/12 00:19

Description

In order to perform upgrades or other maintenance, it is useful to be able to perform a rolling restart of the journal nodes while the NameNode is active.

Currently, this does not work, because the NN only picks up restarted JNs again on the beginning of the next log segment. So, if the NN does not roll after each node is restarted in turn, the NN will eventually fail to commit to a quorum and crash.