[HDFS-9119] Discrepancy between edit log tailing interval and RPC timeout for transitionToActive

• Type: Bug
• Status: Patch Available
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 2.7.1
• Component/s: ha
• Assignee: Zhe Zhang
• Reporter: Zhe Zhang
• Created: 21/Sep/15 22:23
• Updated: 07/Jan/17 01:25

Description

EditLogTailer on standby NameNode tails edits from active NameNode every 2 minutes. But the transitionToActive RPC call has a timeout of 1 minute.

If active NameNode encounters very intensive metadata workload (in particular, a lot of AddOp and MkDir operations to create new files and directories), the amount of updates accumulated in the 2 mins edit log tailing interval is hard for the standby NameNode to catch up in the 1 min timeout window. If that happens, the FailoverController will timeout and give up trying to transition the standby to active. The old ANN will resume adding more edits. When the SbNN finally finishes catching up the edits and tries to become active, it will crash.