[MongoDB 3.6 ] When does WiredTiger open or close the file handles?

[kongfu-cat]

I’m using MongoDB 3.6 in replicaSet mode

I found that the database query speed was slow when many wt files were opened

I found this issue https://jira.mongodb.org/browse/WT-8413

And I have some questions:

1. When does WiredTiger will open the file handles?
2. When does WiredTiger will close the file handles?
3. Whether it is different in the replicaSet mode?
4. Is there a way to reduce the close_ idle_ time, which default is about 28h?

[steevej (Steeve Juneau)]

I have no answers for your questions.

WT cannot predict when it will need to read or write to the file. As a good practice, it probably tries to keep the file open as long as possible for efficiency reasons.

And

@kongfu-cat

query speed was slow when many wt files were opened

might simply be the symptom of insufficient resources for the workload which might be the result of the massive number of collections anti-pattern.