[SERVER-33493] Have WT RTT rollback keep correct counts Created: 26/Feb/18  Updated: 29/Oct/23  Resolved: 29/Mar/18

Status: Closed
Project: Core Server
Component/s: Replication, Storage
Affects Version/s: None
Fix Version/s: 3.7.4

Type: Task Priority: Major - P3
Reporter: Daniel Gottlieb (Inactive) Assignee: Judah Schvimer
Resolution: Fixed Votes: 0
Labels: rollback-non-functional
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Related
is related to SERVER-33488 WT SizeStorer dislikes RTT Closed
Backwards Compatibility: Fully Compatible
Sprint: Repl 2018-03-26, Repl 2018-04-09
Participants:

 Description   

SERVER-33488 describes how counts in RTT WT can diverge with reality across restarts. This ticket is for correcting counts across rollbacks. The proposal:

Have the rollback op observer track the inserts/deletes being rolled back for each collection/UUID. Use this information to adjust counts.

I expect this correction to not be crash-resistant so long as replication truncates the oplog before recovering forward from the stable point to the common point. In general, WT already has problems keeping correct counts across crashes.



 Comments   
Comment by Githook User [ 29/Mar/18 ]

Author:

{'email': 'judah@mongodb.com', 'name': 'Judah Schvimer', 'username': 'judahschvimer'}

Message: SERVER-33493 add jstest collection count validation
Branch: master
https://github.com/mongodb/mongo/commit/f2de49da9b28ee4e04534733db2748eae9e84124

Comment by Githook User [ 29/Mar/18 ]

Author:

{'email': 'judah@mongodb.com', 'name': 'Judah Schvimer', 'username': 'judahschvimer'}

Message: SERVER-33493 Have WT RTT rollback keep correct counts
Branch: master
https://github.com/mongodb/mongo/commit/d3aa30ddc4456422b1adeec437abb8efe3d4cfec

Comment by Gregory McKeon (Inactive) [ 06/Mar/18 ]

alyson.cabral Can you talk to Eliot and see what our plan is for this?

Comment by Judah Schvimer [ 28/Feb/18 ]

As part of this work, the rollback test fixture should begin to ensure that all collection fast-counts are equal to the equivalent itcount() result.

Comment by Gregory McKeon (Inactive) [ 27/Feb/18 ]

alyson.cabral can you comment on how important having correct collection counts across rollbacks be for downstream consumers?

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