[SERVER-36394] mongos should reset chunk size tracking information when autosplit = false or splitvector returns too few split points Created: 01/Aug/18  Updated: 29/Oct/23  Resolved: 31/Jul/19

Status: Closed
Project: Core Server
Component/s: Sharding
Affects Version/s: None
Fix Version/s: 3.6.14, 4.0.12, 3.4.23

Type: Bug Priority: Major - P3
Reporter: Matthew Saltz (Inactive) Assignee: Matthew Saltz (Inactive)
Resolution: Fixed Votes: 0
Labels: neweng
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Backports
Related
is related to SERVER-5375 poor mongos insert/update performance... Closed
Backwards Compatibility: Fully Compatible
Operating System: ALL
Backport Requested:
v3.6, v3.4
Sprint: Sharding 2019-07-15, Sharding 2019-07-29, Sharding 2019-08-12
Participants:
Case:

 Description   

Currently, if the cluster is configured to turn off autosplitting, mongos still tracks the estimated size of each chunk that gets written to through it. This is fine, except that at this line, we refresh the balancer configuration from the config server, and if we don't set the chunk size back to zero, we'll continue to reach this line (because shouldSplit will return true) for every single insert. In other words, once a chunk reaches splitting size and the autosplitter is off, we'll query the config server for every single insert until that chunk is split manually or through some other means. This is unnecessary and hurts performance. We should at least reset the chunk size to zero so we won't try to split it again until many more inserts have been received.



 Comments   
Comment by Githook User [ 31/Jul/19 ]

Author:

{'name': 'Matthew Saltz', 'username': 'saltzm', 'email': 'matthew.saltz@mongodb.com'}

Message: SERVER-36394 Don't refresh balancer configuration for autosplit if autosplit is currently disabled
Branch: v3.4
https://github.com/mongodb/mongo/commit/265375d0f69a5ffb4b11ea71f4064539ad26710d

Comment by Githook User [ 31/Jul/19 ]

Author:

{'name': 'Matthew Saltz', 'email': 'matthew.saltz@mongodb.com', 'username': 'saltzm'}

Message: SERVER-36394 Don't refresh balancer configuration for autosplit if autosplit is currently disabled

(cherry picked from commit 4a0def0129ae5aa6c8ea951b5c452c8938cf4d83)
Branch: v3.6
https://github.com/mongodb/mongo/commit/0b8eaf330fafce91a5f31f97f63703e42ba10b68

Comment by Githook User [ 31/Jul/19 ]

Author:

{'name': 'Matthew Saltz', 'email': 'matthew.saltz@mongodb.com', 'username': 'saltzm'}

Message: SERVER-36394 Don't refresh balancer configuration for autosplit if autosplit is currently disabled
Branch: v4.0
https://github.com/mongodb/mongo/commit/4a0def0129ae5aa6c8ea951b5c452c8938cf4d83

Comment by Matthew Saltz (Inactive) [ 04/Dec/18 ]

Oops, I believe it should be this, and it's only in 4.0 and prior.

Comment by Blake Oler [ 04/Dec/18 ]

matthew.saltz the line you linked is outdated (the file now no longer has that many lines). Where is said line now?

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