[SERVER-38599] Write downgrade test for two phase drop Created: 13/Dec/18  Updated: 29/Oct/23  Resolved: 24/Jan/19

Status: Closed
Project: Core Server
Component/s: Storage
Affects Version/s: None
Fix Version/s: 4.1.8

Type: Task Priority: Major - P3
Reporter: Benety Goh Assignee: Xiangyu Yao (Inactive)
Resolution: Fixed Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Backwards Compatibility: Fully Compatible
Sprint: Storage NYC 2019-01-28
Participants:

 Description   

We need to verify that an unfinished 4.2-style two phase drop (defer drop in WT) could be handled nicely on startup of 4.0 binary.

If an 4.2-style two phase drop is unfinished on the shutdown of 4.2 binary, it means the first phase (dropping metadata in the catalog) is completed (committed but not checkpointed yet - metadata still exists from disk's perspective) but the second phase (dropping ident in WT) is not. And a "dropCollection" oplog entry is written (committed and persistent on disk in the form of WT journal).

On the startup of 4.0 binary, MongoDB will start with the last checkpoint which has the original collection and replay the oplog entries including that "dropCollection". The collection will be dropped with 4.0-style (old way) two phase drop mechanism.4.0 binary does not need to do anything related to the 4.2-style two phase drop in this case.

This applies to both primary and secondary nodes. This ticket is to write a downgrade test to verify the theory.



 Comments   
Comment by Githook User [ 24/Jan/19 ]

Author:

{'username': 'xy24', 'email': 'xiangyu.yao@mongodb.com', 'name': 'Xiangyu Yao'}

Message: SERVER-38599 Write downgrade test for two phase drop
Branch: master
https://github.com/mongodb/mongo/commit/29813aa638bd2c6ab55962a63882edac3dcb1032

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