[HDFS-10887] Provide admin/debug tool to dump block map

• Type: New Feature
• Status: Patch Available
• Priority: Major
• Resolution: Unresolved
• Component/s: hdfs, namenode
• Assignee: Yongjun Zhang
• Reporter: Yongjun Zhang
• Created: 22/Sep/16 06:44
• Updated: 03/Oct/16 21:57

Description

From time to time, when NN restarts, we see

"The reported blocks X needs additional Y blocks to reach the threshold 0.9990 of total blocks Z. Safe mode will be turned off automatically.

We'd wonder what these blocks that still need block reports are, and what DNs they could possibly be located, what happened to these DNs.

This jira to to propose a new admin or debug tool to dump the block map info with the blocks that have fewer than minRepl replicas.