[HBASE-25872] Add documentation for LoadBalancer about synchronization

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 3.0.0-alpha-1, 2.5.0
• Component/s: Balancer, documentation
• Hadoop Flags: Reviewed
• Assignee: Duo Zhang
• Reporter: Duo Zhang
• Created: 09/May/21 13:08
• Updated: 17/May/21 18:37
• Resolved: 17/May/21 02:38

Description

In general, the balanceCluster call is not thread safe and we only allow one balanceCluster call at the same time, so we need to synchronize balanceCluster, onConfigurationChange, and setClusterMetrics(which will be called periodically, maybe we should rename it to updateClusterMetrics).

Most setters do not need to be synchronized as they will only be called once before initialization.

And anothe group of methods are XXXAssignment, these methods should be thread safe and should not be synchronized to improve the assignment performance.

Issue Links

• links to: GitHub Pull Request #3267