[HBASE-11740] RegionStates.getRegionAssignments() gets stuck on clone

• Type: Sub-task
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.99.0, 0.98.6
• Component/s: Region Assignment
• Hadoop Flags: Reviewed
• Assignee: Virag Kothari
• Reporter: Virag Kothari
• Created: 14/Aug/14 04:12
• Updated: 06/Apr/18 17:51
• Resolved: 15/Aug/14 17:44

Description

This happens in processDeadServersAndRegionsInTransition() on Master startup. RegionAssigments is a tree map and TreeMap.clone() is expensive as it builds a tree from sorted data (Order of n). There were a million entries in RegionAssigments and from jstack, thread was stuck in TreeMap.buildFromSorted() for couple of hours.
Instead of this shadow clone, wrapping as an unmodifiable Map should be enough.