[HDFS-10822] Log DataNodes in the write pipeline

• Type: Improvement
• Status: Resolved
• Priority: Trivial
• Resolution: Fixed
• Affects Version/s: 2.6.0
• Fix Version/s: 2.9.0, 3.0.0-alpha2
• Component/s: hdfs-client
• Labels: supportability
• Target Version/s: 2.8.0
• Assignee: John Zhuge
• Reporter: John Zhuge
• Created: 31/Aug/16 19:21
• Updated: 02/Sep/16 21:46
• Resolved: 02/Sep/16 18:04

Description

Trying to diagnose a slow HDFS flush, taking longer than 10 seconds, but did not know which DNs were involved in the write pipeline. Of course, I could search NN log for the list of DNs, but it might not be possible sometimes or convenient.

Propose to add a DEBUG trace to DataStreamer#setPipeline to print the list of DNs in the pipeline.

BTW, we do print the list of DNs during pipeline recovery.