[HDFS-15594] Lazy calculate live datanodes in safe mode tip

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 3.4.0
• Component/s: namenode
• Labels: pull-request-available
• Hadoop Flags: Reviewed
• Assignee: Ye Ni
• Reporter: Ye Ni
• Created: 23/Sep/20 19:54
• Updated: 25/Sep/20 16:49
• Resolved: 25/Sep/20 16:48

Description

Safe mode tip is printed every 20 seconds.

This change is to calculate live datanodes until reported block threshold is meet.
Old 

STATE* Safe mode ON. The reported blocks 111054015 needs additional 27902753 blocks to reach the threshold 0.9990 of total blocks 139095856. The number of live datanodes 2531 has reached the minimum number 1. Safe mode will be turned off automatically once the thresholds have been reached.

New 

STATE* Safe mode ON. 
The reported blocks 134851250 needs additional 3218494 blocks to reach the threshold 0.9990 of total blocks 138207947.
The number of live datanodes is not calculated since reported blocks hasn't reached the threshold. Safe mode will be turned off automatically once the thresholds have been reached.

 

Issue Links

• is related to: HDFS-14859 Prevent unnecessary evaluation of costly operation getNumLiveDataNodes when dfs.namenode.safemode.min.datanodes is not zero
• is related to: HDFS-14171 Performance improvement in Tailing EditLog
• is related to: HDFS-14632 Reduce useless #getNumLiveDataNodes call in SafeModeMonitor
• links to: GitHub Pull Request #2332