[SERVER-42598] Periodic slow queries Created: 02/Aug/19  Updated: 05/Aug/19  Resolved: 05/Aug/19

Status: Closed
Project: Core Server
Component/s: Performance, WiredTiger
Affects Version/s: 4.0.9
Fix Version/s: None

Type: Bug Priority: Major - P3
Reporter: David Liao Assignee: Danny Hatcher (Inactive)
Resolution: Done Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified
Environment:

Ubuntu 16.04 LTS, AWS i3.16xl


Attachments: Zip Archive diag.zip    
Operating System: ALL
Steps To Reproduce:

Happens very regularly

Participants:

 Description   

Hi, we're seeing periodic slow queries in our mongo logs for queries on _id and is indexed. We recently made lots of effort on trimming down our database size as well as index size and synced a new replica set so compaction happened, our indexes now should fit in memory but we are still seeing poor performance on basic queries.

Attached you can find our diagnostics data



 Comments   
Comment by Danny Hatcher (Inactive) [ 05/Aug/19 ]

From a quick look at the diagnostics, I can see that you still have some un-optimized queries. At points in time, the ratio of index keys vs documents scanned reaches 79,101.667/s : 812,876.167/s. The ideal ratio is 1:1.

The SERVER project is for bugs and feature requests and this looks like a query optimization issue. As such, I encourage you to ask our community for further help by posting on the mongodb-user group or on Stack Overflow with the mongodb tag.

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