[HDFS-2017] A partial rollback cause the new changes done after upgrade to be visible after rollback

• Type: Bug
• Status: Resolved
• Priority: Minor
• Resolution: Not A Problem
• Affects Version/s: 0.20.1
• Component/s: namenode
• Labels: rollback upgrade
• Assignee: Unassigned
• Reporter: SreeHari
• Created: 31/May/11 10:22
• Updated: 14/Oct/14 02:09
• Resolved: 14/Oct/14 02:09

Description

This is the scenario :

Namenode has 3 name dirs configured ..
1) Namenode upgrade starts - Upgrade fails after 1st directory is upgraded (2nd and 3rd dir is left unchanged ..)

{ like , Namenode process down }

2) Namenode starts and new files written ..
3) Namenode shutdown and rollbacked

Since Namenode is saving the latest image dir(the upgraded 1st dir since checkpointtime is incremented during upgrade for this dir) will be loaded and saved to all dirs during loadfsimage ..

But if a ROLLBACK is done , the 1st dir will be rolled back (the older copy becomes current and its checkpointtime is now LESS than other dirs ..) and others left behind since they dont contain previous .. Now during loadfsimage , the 2nd dir will be selected since it has the highest checkpoint time and saved to all dirs (including 1st ) .. Now due to this , the new changes b/w UPGRADE and ROLLBACK present in 2nd dir gets reflected even after ROLLBACK ..

This is not the case with a SUCCESSFUL Upgrade/Rollback (New changes lost after rollback)..