[SERVER-27672] Unnecessary rollback for a hidden node after a priority takeover reconfig Created: 13/Jan/17  Updated: 23/Jan/17  Resolved: 23/Jan/17

Status: Closed
Project: Core Server
Component/s: Replication
Affects Version/s: 3.2.9
Fix Version/s: None

Type: Bug Priority: Major - P3
Reporter: CenZheng Assignee: Kelsey Schubert
Resolution: Duplicate Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Attachments: File repl_log.tar.gz    
Issue Links:
Duplicate
duplicates SERVER-27403 Consider term and rbid when validatin... Closed
Operating System: ALL
Participants:

 Description   

Hi, I have a P/S/H(priority 2/1/0) replset using 3.2.9 with replicaton protocal v1. And I noticed that during a reconfiging to (1/2/0) procedure, the Hidden node entered rollback state because he choosed the original Primary as his new sync source after the new election, which soon rollbacked too because he is no longer the Primary. This Hidden entered rollback because he has a higer term(the latest right term synced from the new Primary) than the sync source(the original Primary). But I think this rollback is unnecessary. Is this a sync source choosen bug? I have all the 3 nodes' mongod.log if you need. Thanks!



 Comments   
Comment by Kelsey Schubert [ 23/Jan/17 ]

Hi zhcn381,

Thank you for providing the logs. After review, appears that you are hitting SERVER-27403. Please note that we have made a number of improvements in MongoDB 3.4 to reduce the frequency of rollbacks in replica sets with various priority levels. If this is an issue for you, I would recommend that you consider upgrading to MongoDB 3.4 as well as watching SERVER-27403 for updates.

King regards,
Thomas

Comment by CenZheng [ 16/Jan/17 ]

Hi Thomas,
I have uploaded the replication related log in the attachments here. Thanks~

Comment by Kelsey Schubert [ 13/Jan/17 ]

Hi zhcn381,

Thanks for reporting this behavior. So we can investigate, would you please upload the logs for all three nodes to this secure portal?

Kind regards,
Thomas

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