[SERVER-4519] WRITETOJOURNAL and WRITETODATAFILES should not block readers Created: 18/Dec/11  Updated: 06/Dec/22  Resolved: 22/Mar/17

Status: Closed
Project: Core Server
Component/s: MMAPv1, Storage
Affects Version/s: None
Fix Version/s: None

Type: Improvement Priority: Major - P3
Reporter: Dwight Merriman Assignee: Backlog - Storage Execution Team
Resolution: Done Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Assigned Teams:
Storage Execution
Participants:

 Description   

we should verify this, have a test.

historically they have, i believe - when writes queue up that is. however they need not
and may not now with the new ExcludeAllWrites class.

we could simply sleep() a long time in the writing to data fiels or journals while certain activity underway and verify we can still do queries.



 Comments   
Comment by Geert Bosch [ 22/Mar/17 ]

This should be closed now: actual flushing and journal writing is now done in separate threads, so reads can proceed in parallel. There are still some critical sections of course, but we're not going to improve over what we have now.

Comment by Dwight Merriman [ 18/Dec/11 ]

also, if these are bottlnecking let's be sure there are ways to tell what is up – which may already be the case in the serverStatus().dur stats – when tested let's look at that and see if there is sufficient telemetry to be clear on these things

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