[SERVER-38310] Oplog information collection stalls FTDC Created: 29/Nov/18  Updated: 29/Oct/23  Resolved: 13/Dec/18

Status: Closed
Project: Core Server
Component/s: None
Affects Version/s: None
Fix Version/s: 4.1.7

Type: Bug Priority: Major - P3
Reporter: Bruce Lucas (Inactive) Assignee: Mark Benvenuto
Resolution: Fixed Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Related
is related to SERVER-37625 Collect diagnostic information for re... Closed
Backwards Compatibility: Fully Compatible
Operating System: ALL
Sprint: Security 2018-12-17
Participants:

 Description   

In SERVER-37625 we added oplog information collection to ftdc in order to have oplog window information (oplog earliest and latest times). This has an unfortunate side effect of stalling ftdc when the system is under stress in waitForAllEarlierOplogWritesToBeVisible while reading the earliest and latest documents from the oplog. This is bad because when the system is under stress is exactly when we need ftdc the most.

Generally the oplog is large enough that earliest and latest times don't change very quickly relative to the size of the oplog, so it would be ok if this information was a little stale. Maybe we can use a (short) timeout on this read from the oplog, and if it times out use the last collected information? Or maybe we can do this read without calling waitForAllEarlierOplogWritesToBeVisible because for statistics purposes (I think) it doesn't really matter whether earlier oplog writes are visible?



 Comments   
Comment by Githook User [ 13/Dec/18 ]

Author:

{'username': 'markbenvenuto', 'email': 'mark.benvenuto@mongodb.com', 'name': 'Mark Benvenuto'}

Message: SERVER-38310 Oplog information collection stalls FTDC

Revert "SERVER-37625 Add oplog earliest time to FTDC"

This reverts commit dd17c8ad0fa2b9b71df5f0b00ec77f58b55c4a5b.
This reverts commit 98ca46fda7788d13cca31569d6e722699514c1fa.
Branch: master
https://github.com/mongodb/mongo/commit/6d900523fac41857c7fe05a34dd480d1f4b56ec8

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