[SERVER-47205] Stopping dropping snapshots after safe reconfig that does not change writeConcernMajorityJournalDefault Created: 31/Mar/20  Updated: 01/Dec/23  Resolved: 17/Apr/20

Status: Closed
Project: Core Server
Component/s: Replication
Affects Version/s: None
Fix Version/s: 4.4.0-rc3, 4.7.0

Type: Improvement Priority: Major - P3
Reporter: Tess Avitabile (Inactive) Assignee: Siyuan Zhou
Resolution: Fixed Votes: 0
Labels: former-quick-wins
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Backports
Depends
is depended on by SERVER-47142 Check primary before writing replset ... Closed
Related
related to SERVER-46516 Majority write concern is blocked by ... Closed
related to SERVER-47142 Check primary before writing replset ... Closed
related to SERVER-40649 Drop snapshots for reconfig via heart... Backlog
related to SERVER-83092 Eliminate the unnecessary majority ch... Closed
is related to SERVER-47206 Majority commit point is not set back... Backlog
Backwards Compatibility: Fully Compatible
Backport Requested:
v4.4
Sprint: Repl 2020-05-04
Participants:

 Description   

After a reconfig, we drop snapshots, since the definition of majority-committed can change. However, all this does is set _currentCommittedSnapshot to none. It does not change the
_lastCommittedOpTimeAndWallTime in the TopologyCoordinator. This means that the next time we set _currentCommittedSnapshot, either due to the JournalFlusher or replSetUpdatePosition, we will refuse to set _lastCommittedOpTimeAndWallTime backward, so _currentCommittedSnapshot can be set to its previous value from before the reconfig. This means that dropping snapshots after reconfig doesn’t accomplish anything.

The safe reconfig protocol guarantees that operations committed in the old config will never roll back, so we can stop dropping snapshots after a safe reconfig that does not change writeConcernMajorityJournalDefault.



 Comments   
Comment by Githook User [ 24/Apr/20 ]

Author:

{'name': 'Siyuan Zhou', 'email': 'siyuan.zhou@mongodb.com', 'username': 'visualzhou'}

Message: SERVER-47205 Stopping dropping snapshots after safe reconfig that does not change writeConcernMajorityJournalDefault

(cherry picked from commit a397fc442440984fca2ab37f491759745979ab2d)
Branch: v4.4
https://github.com/mongodb/mongo/commit/70b693235173db39960fb5828b7594ce2c1f8eae

Comment by Siyuan Zhou [ 17/Apr/20 ]

The backport of this ticket is necessary for SERVER-47205.

Comment by Githook User [ 17/Apr/20 ]

Author:

{'name': 'Siyuan Zhou', 'email': 'siyuan.zhou@mongodb.com', 'username': 'visualzhou'}

Message: SERVER-47205 Stopping dropping snapshots after safe reconfig that does not change writeConcernMajorityJournalDefault
Branch: master
https://github.com/mongodb/mongo/commit/a397fc442440984fca2ab37f491759745979ab2d

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