[SERVER-46150] Disable unit test CreateAndCheckForCachePressure Created: 14/Feb/20  Updated: 29/May/20  Resolved: 29/May/20

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

Type: Task Priority: Major - P3
Reporter: Sulabh Mahajan Assignee: Dianna Hohensee (Inactive)
Resolution: Duplicate Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Backports
Duplicate
duplicates SERVER-47997 Remove cachePressureThreshold and isC... Closed
Related
is related to WT-5499 Replace lookaside score statistic wit... Closed
is related to WT-5576 Temporarily add lookaside score stat ... Closed
Backport Requested:
v4.4
Sprint: Execution Team 2020-06-15
Participants:

 Description   

Lookaside score from WiredTiger fed into the calculation used for MongoDB snapshot window size calculation. Since the lookaside is being replaced by the history store and the cache-usage / cache-pressure behaviour and statistics are not clear at the moment, there is no replacement available to the lookaside score. While we investigate a replacement in the future (WT-5499), we have decided to set the lookaside score to 0 (WT-5576), but this will lead to the snapshot window not adjusting to the cache pressure MongoDB unit test tries to create.

This ticket will stop running the unit test CreateAndCheckForCachePressure, till WT-5499 comes up with an alternate way to determine cache pressure.



 Comments   
Comment by Dianna Hohensee (Inactive) [ 29/May/20 ]

SERVER-47997 Removed this unit test. Closing as a dupe thereof.

Comment by Donald Anderson [ 24/Apr/20 ]

Thanks for the context on this. It's quite possible that there is nothing to do for this. I'll assign it to the Execution team backlog to just confirm that the test is removed or appropriately disabled.

Comment by Dianna Hohensee (Inactive) [ 24/Apr/20 ]

Sure, you can assign it to execution to remove the test.

I thought this unit test was already disabled? Hasn't the lookaside score been set to a constant 0 with the WT durable history drop, making the CreateAndCheckForCachePressure unit test fail? I don't see any BFG/BF tickets.

WT-5499 is supposed to revisit whether any performance issues arise with maintaining a 5 second window of history. If the lookaside score is set to a constant 0 right now, MongoDB will default to establishing a 5 (adjustable server setting) second history window by not moving the oldest_timestamp forward until there is a 5 second window behind the stable_timestamp. Aside from checking whether there are any performance issues keeping extra history, I do not think there is any further work to be done by WT for MongoDB v4.4+ on this subject.

Comment by Donald Anderson [ 23/Apr/20 ]

dianna.hohensee, I'm wondering what actions the storage engine group can do about this ticket?  We don't have a lookaside table going forward and there is currently no equivalent way to measure cache pressure. If this test simply doesn't make sense anymore can I assign this to your team to deal with removing it?

(alexander.gorrod thought you might best answer these questions).

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