[SERVER-51248] Using _secondaryThrottle and _waitForDelete leads a high number of chunks Created: 30/Sep/20 Updated: 05/Nov/20 Resolved: 05/Nov/20 |
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| Status: | Closed |
| Project: | Core Server |
| Component/s: | None |
| Affects Version/s: | None |
| Fix Version/s: | None |
| Type: | Bug | Priority: | Major - P3 |
| Reporter: | Vinicius Grippa | Assignee: | Eric Sedor |
| Resolution: | Done | Votes: | 0 |
| Labels: | None | ||
| Remaining Estimate: | Not Specified | ||
| Time Spent: | Not Specified | ||
| Original Estimate: | Not Specified | ||
| Attachments: |
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| Operating System: | ALL |
| Participants: |
| Description |
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Performing a synthetic workload I noticed a very different number of chunks and an error rate in the balancer when using the option: Below are the test results:
And with the settings in place:
It seems like an issue since Mongo "gives up" about splitting the chunk and I'm afraid this can lead to jumbo chunks. On the other hand, with the settings enabled, I can observe an increased load on the shards (probably due to the write concern majority). |
| Comments |
| Comment by Eric Sedor [ 05/Nov/20 ] | ||||
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Thanks as well, vgrippa@gmail.com! | ||||
| Comment by Vinicius Grippa [ 05/Nov/20 ] | ||||
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Hi Eric, That makes sense. Thanks a lot for your time checking this. | ||||
| Comment by Eric Sedor [ 04/Nov/20 ] | ||||
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Hi vgrippa@gmail.com and thanks for your patience here. Big picture, we expect chunk counts to vary depending on a variety of factors that are not necessarily bugs. I am not able to reproduce a clear relationship between those settings and a higher chunk count. A few things that are relevant to this scenario:
If it's possible for you to narrow down this scenario to a specific chunk split that should or should not occur, it would help us consider the possibility of a bug. Otherwise, we'd recommend upgrading to later versions of MongoDB to ensure the latest sharded collection behavior is in place. Does this make sense? Sincerely, | ||||
| Comment by Vinicius Grippa [ 06/Oct/20 ] | ||||
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Hi Eric,
1) What is the version of MongoDB 2) Is the first sh.status() output you provided for default settings? Above it looks like provided settings are the same for each case 3) How is data being added to the collection Then creating data:
Next, on MongoS:
Then importing the data:
4) Is the collection sharded before or after adding data | ||||
| Comment by Eric Sedor [ 05/Oct/20 ] | ||||
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Can you please clarify some aspects of the description and provide additional details? In particular: 1) What is the version of MongoDB |