[HDFS-3863] QJM: track last "committed" txid

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: QuorumJournalManager (HDFS-3077)
• Fix Version/s: QuorumJournalManager (HDFS-3077)
• Component/s: ha
• Hadoop Flags: Reviewed
• Assignee: Todd Lipcon
• Reporter: Todd Lipcon
• Created: 28/Aug/12 21:12
• Updated: 05/Sep/12 04:13
• Resolved: 05/Sep/12 04:13

Description

Per some discussion with Chao Shi here, we should keep track of the "last committed txid" on each JournalNode. Then during any recovery operation, we can sanity-check that we aren't asked to truncate a log to an earlier transaction.

This is also a necessary step if we want to support reading from in-progress segments in the future (since we should only allow reads up to the commit point)