[SERVER-33220] Understanding number of file descriptors needed by mongod process Created: 09/Feb/18  Updated: 12/Feb/18  Resolved: 11/Feb/18

Status: Closed
Project: Core Server
Component/s: None
Affects Version/s: None
Fix Version/s: None

Type: Question Priority: Major - P3
Reporter: onkar Assignee: Dmitry Agranat
Resolution: Duplicate Votes: 0
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified
Environment:

3.0.15


Issue Links:
Duplicate
is duplicated by SERVER-17675 Support file per database for WiredTiger Closed
Participants:

 Description   

Hi,
Currently I am using Mongodb 3.0.15 with Wiredtiger storage engine. I am facing "too many open files" issue while performing mongodump. we have approximately 3000 databases having 10 collections each. I have increased "max open files limit" for mongod process. I have changed "max open files limit" to 1 lac from 64000. I can see 62000 file descriptors for mongod process using lsof command even though I am not performing any operation on it. I have read that Wiredtiger tries to open 2 files for each collection and 1 for each index. If so is there a way to limit number of file descriptors and how can I scale going forward as in practice kernel has some limit on number of file descriptor. Please tell me if I am missing something. Thanks in advance.



 Comments   
Comment by onkar [ 12/Feb/18 ]

Thanks for response. We are already planning to move towards ATLAS to scale horizontally.

Comment by Dmitry Agranat [ 11/Feb/18 ]

Hello onkarb,

Thank you for the question.

MongoDB holds a file descriptor for every data file. As in WiredTiger, this results in a file for each collection + a file for each index.

If so is there a way to limit number of file descriptors

This is tracked in SERVER-17675

how can I scale going forward as in practice kernel has some limit on number of file descriptor

When increasing the capacity of a single server is reaching its limit, we recommend horizontal scaling through sharding

I'm going to close this ticket as a duplicate of SERVER-17675, which you may want to vote for and follow for updates.

Thank you,
Dima

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