[SERVER-50777] Don't widen target snapshot window for in-memory configurations (v4.4) Created: 07/Sep/20  Updated: 14/Sep/20  Resolved: 14/Sep/20

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

Type: Bug Priority: Major - P3
Reporter: Alex Cameron (Inactive) Assignee: Alex Cameron (Inactive)
Resolution: Won't Fix Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Depends
Operating System: ALL
Sprint: Storage - Ra 2020-09-07, Storage - Ra 2020-09-21
Participants:
Linked BF Score: 25
Story Points: 0

 Description   

As I was diagnosing a test failure, I noticed this sequence of events:

  • The body of execCommandDatabase throws a SnapshotTooOld error due to trying to read earlier than the oldest.
  • When this happens, we try to increase the target snapshot window size to make it less likely for this to happen for subsequent operations.
  • We expect this window size to be 0 for in-memory configurations so we trip up an invariant later down the track.

The way I understand it, this scenario makes sense and is ok. The only problem is the way we're handling the exception by widening the snapshot window. We shouldn't do this if we're running an in-memory configuration and haven't enabled test commands.



 Comments   
Comment by Alex Cameron (Inactive) [ 14/Sep/20 ]

dianna.hohensee lingzhi.deng
Let me know if you'd rather have this change merged in. But for now, I'm going to just close this since the proper fix is underway.

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