[HDFS-12140] Remove BPOfferService lock contention to get block pool id

• Type: Bug
• Status: Resolved
• Priority: Critical
• Resolution: Fixed
• Affects Version/s: 2.8.0
• Fix Version/s: 2.9.0, 3.0.0-beta1, 2.8.2
• Component/s: datanode
• Target Version/s: 2.8.2
• Hadoop Flags: Reviewed
• Assignee: Daryn Sharp
• Reporter: Daryn Sharp
• Created: 14/Jul/17 14:59
• Updated: 25/Jul/17 04:42
• Resolved: 14/Jul/17 21:19

Description

The block pool id is protected by a lock in BPOfferService. This creates excessive contention especially for xceivers threads attempting to queue IBRs and heartbeat processing. When the latter is delayed due to excessive FSDataset lock contention, it causes pipelines to collapse.

Accessing the block pool id should be lockless after registration.