[HBASE-19989] READY_TO_MERGE and READY_TO_SPLIT do not update region state correctly

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.3.1, 1.4.1
• Fix Version/s: 1.3.2, 1.4.3
• Hadoop Flags: Reviewed
• Assignee: Ben Lau
• Reporter: Ben Lau
• Created: 13/Feb/18 02:12
• Updated: 01/Feb/19 20:00
• Resolved: 28/Feb/18 01:46

Description

Region state transitions do not work correctly for READY_TO_MERGE/SPLIT.  thiruvel and I noticed this is due to break statements being in the wrong place in AssignmentManager.  This allows a race condition for example in which one of the regions being merged could be moved concurrently, resulting in the merge transaction failing and then double assignment and/or dataloss.  This bug appears to only affect branch-1 (for example 1.3 and 1.4) and not branch-2 as the relevant code in AM has since been rewritten.