[HDFS-8647] Abstract BlockManager's rack policy into BlockPlacementPolicy

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 2.8.0, 2.7.3, 2.6.4, 3.0.0-alpha1
• Target Version/s: 2.6.4
• Assignee: Brahma Reddy Battula
• Reporter: Ming Ma
• Created: 23/Jun/15 04:58
• Updated: 30/Aug/16 01:32
• Resolved: 21/Oct/15 15:31

Description

Sometimes we want to have namenode use alternative block placement policy such as upgrade domains in HDFS-7541.

BlockManager has built-in assumption about rack policy in functions such as useDelHint, blockHasEnoughRacks. That means when we have new block placement policy, we need to modify BlockManager to account for the new policy. Ideally BlockManager should ask BlockPlacementPolicy object instead. That will allow us to provide new BlockPlacementPolicy without changing BlockManager.

Issue Links

• is related to: HDFS-8688 replace shouldCheckForEnoughRacks with hasClusterEverBeenMultiRack
• is related to: HDFS-8689 move hasClusterEverBeenMultiRack to NetworkTopology
• relates to: HDFS-9501 TestBalancer#testBalancerWithPinnedBlocks fails in branch-2.7