Operational Defect Database

BugZero found this defect 2340 days ago.

MongoDB | 436831

[SERVER-31344] Process limit not handled gracefully

Last update date:


Affected products:

MongoDB Server

Affected releases:


Fixed releases:

No fixed releases provided.



Hi! We've got problem with mongod with unstable behaviour, when replicaset had constantly rebooting instances and almost no master elected.

Top User Comments

acm commented on Tue, 17 Oct 2017 16:35:27 +0000: Hi yasek - I'm closing this ticket since it doesn't seem to have any additional activity. Please feel free to re-open or add additional comments if there is any additional help I can provide. acm commented on Mon, 9 Oct 2017 20:37:49 +0000: yasek - I'd recommend over-provisioning w.r.t. to any ulimits. We do not currently attempt to gracefully degrade when we are close to violating them. We treat ulimits as quotas that the user has chosen to enforce on us, and consider a violation of those limits as an indication that the system is misbehaving and should be terminated by the OS as the next level of error handling. Attempting to set the ulimits at or just above your expected capacity means that transient events could push you into failure. I would advise dropping ulimit restrictions entirely or setting them to a constant multiple of your expected maximum. To answer your specific question, you are not safe to handle 64k connections with a ulimit set at 64k processes, as mongodb can and does make use of background threads. Please let me know if there is any additional information I can provide to help you set appropriate values. thomas.schubert commented on Fri, 6 Oct 2017 16:21:33 +0000: Hi yasek, If you expect that your that your workload will generate close to 64k connections, I would recommend increasing your limits to ensure that mongod can continue to access required resources under load. I've modified the ticket to summary to describe work to enable mongod to more gracefully approach these limits and marked it to be considered by our Platforms Team - please continue to watch for updates. Kind regards, Kelsey yasek commented on Tue, 3 Oct 2017 06:37:22 +0000: anonymous.user, any suggestions? yasek commented on Sat, 30 Sep 2017 19:07:49 +0000: Yes, I realize, that increasing ulimits could resolve this issue on such workload. Actually, we had greater limits and heavier workload. Is there guarantee that having ulimit set to 64k, mongod will be still working after allocating 64k connections? thomas.schubert commented on Sat, 30 Sep 2017 15:28:22 +0000: Hi yasek, Thank you for the report. mongod requires ulimits to be appropriately set for its workload. Please increase your settings to our recommended values and reevaluate the performance of your replica set to confirm that the issue has been resolved. Kind regards, Kelsey

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