[SERVER-55821] remove next_random_sample_size=1000 configuration in the oplog sampling code Created: 06/Apr/21 Updated: 29/Oct/23 Resolved: 06/Jul/21 |
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| Status: | Closed |
| Project: | Core Server |
| Component/s: | None |
| Affects Version/s: | None |
| Fix Version/s: | 5.1.0-rc0 |
| Type: | Bug | Priority: | Major - P3 |
| Reporter: | Keith Bostic (Inactive) | Assignee: | Benety Goh |
| Resolution: | Fixed | Votes: | 0 |
| Labels: | None | ||
| Remaining Estimate: | Not Specified | ||
| Time Spent: | Not Specified | ||
| Original Estimate: | Not Specified | ||
| Issue Links: |
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| Backwards Compatibility: | Fully Compatible | ||||||||||||||||||||
| Operating System: | ALL | ||||||||||||||||||||
| Sprint: | Execution Team 2021-06-14, Execution Team 2021-07-12 | ||||||||||||||||||||
| Participants: | |||||||||||||||||||||
| Description |
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The use of the next_random_sample_size option when creating random cursors on a WiredTiger record store is not applicable anymore due to unbalanced trees being a non-issue in recent MongoDB releases and customer deployments. The work for this ticket involves removing the use of this option from the oplog sampling code in wiredtiger_record_store.cpp for 5.1 and to evaluate removing the support for this option in the WiredTiger storage engine at a later time. PREVIOUS SUMMARY: Investigate slow random cursor operations on oplog Random cursors can be quite slow on a multi-GB oplog table. A customer has experienced slow startup times in 4.2 that they didn't see in 4.0. Based on their logs mongod is spending a lot of time iterating a random cursor though the oplog — in one case it takes 15 minutes to perform 993 cursor->next() calls on a ~26GB oplog. The oplog had only 62590 records, so the average record size is 100s of KB. See |
| Comments |
| Comment by Vivian Ge (Inactive) [ 06/Oct/21 ] |
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Updating the fixversion since branching activities occurred yesterday. This ticket will be in rc0 when it’s been triggered. For more active release information, please keep an eye on #server-release. Thank you! |
| Comment by Githook User [ 05/Jul/21 ] |
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Author: {'name': 'Benety Goh', 'email': 'benety@mongodb.com', 'username': 'benety'}Message: |
| Comment by Githook User [ 04/Jul/21 ] |
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Author: {'name': 'Benety Goh', 'email': 'benety@mongodb.com', 'username': 'benety'}Message: |
| Comment by Githook User [ 03/Jul/21 ] |
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Author: {'name': 'Benety Goh', 'email': 'benety@mongodb.com', 'username': 'benety'}Message: |
| Comment by Benety Goh [ 29/Jun/21 ] |
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We started logging the WiredTiger oplog processing time in |
| Comment by Benety Goh [ 25/Jun/21 ] |
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(Reproducing some of the context from |
| Comment by Keith Bostic (Inactive) [ 06/Apr/21 ] |
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This ticket is a place to investigate and potentially make changes to remove the next_random_sample_size=1000 configuration in the MongoDB server oplog sampling code, see geert.bosch, I apologize for assigning this to you, but I wasn't sure of the right path and you've been flagged on some of the discussions, please don't hesitate to move this as you see fit.
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