[HDFS-528] Add ability for safemode to wait for a minimum number of live datanodes

• Type: New Feature
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.22.0
• Fix Version/s: 0.22.0, 1.1.1
• Component/s: scripts
• Hadoop Flags: Reviewed
• Assignee: Todd Lipcon
• Reporter: Todd Lipcon
• Created: 05/Aug/09 00:17
• Updated: 19/Nov/12 06:53
• Resolved: 18/Nov/10 21:13

Description

When starting up a fresh cluster programatically, users often want to wait until DFS is "writable" before continuing in a script. "dfsadmin -safemode wait" doesn't quite work for this on a completely fresh cluster, since when there are 0 blocks on the system, 100% of them are accounted for before any DNs have reported.

This JIRA is to add a command which waits until a certain number of DNs have reported as alive to the NN.