[HDFS-11742] Improve balancer usability after HDFS-8818

• Type: Bug
• Status: Resolved
• Priority: Blocker
• Resolution: Fixed
• Fix Version/s: 2.9.0, 2.7.4, 3.0.0-beta1, 2.8.2
• Target Version/s: 2.7.4, 3.0.0-beta1, 2.8.1
• Hadoop Flags: Reviewed
• Assignee: Kihwal Lee
• Reporter: Kihwal Lee
• Created: 02/May/17 21:48
• Updated: 25/Jul/17 04:42
• Resolved: 21/Jul/17 15:14

Description

We ran 2.8 balancer with HDFS-8818 on a 280-node and a 2,400-node cluster. In both cases, it would hang forever after two iterations. The two iterations were also moving things at a significantly lower rate. The hang itself is fixed by HDFS-11377, but the design limitation remains, so the balancer throughput ends up actually lower.

Instead of reverting HDFS-8188 as originally suggested, I am making a small change to make it less error prone and more usable.

Issue Links

• depends upon: HDFS-11377 Balancer hung due to no available mover threads
• is broken by: HDFS-8818 Allow Balancer to run faster