High Memory Usage on MongoDB Secondary Server Not Matching Cache + Free Heap | Mongo v7.0.14

Ramkumar_S · 2024-11-11T04:24:35.944Z

Hi Team,

In our 5-node replica set, we’re noticing high memory usage by MongoDB on one of the secondary servers. The cache is configured with default settings, but the combined total of the cache and free heap doesn’t account for MongoDB’s total memory usage. The memory usage keeps increasing by about 12 GB over two days, exceeding the expected cache + free heap values.

We’ve upgraded from version 7.0.9 to 7.0.14, but the issue persists — the memory usage still doesn’t align with the cache configuration. All memory parameters have been tuned according to MongoDB documentation.

Any insights or assistance would be greatly appreciated.

Mongo version: 7.0.14

OS: ubuntu 22.04.3 LTS (Jammy Jellyfish)

root@dbserver04-cds:/home/mydbops# free -h
total used free shared buff/cache available
Mem: 123Gi 65Gi 796Mi 1.0Mi 56Gi 56Gi
Swap: 49Gi 585Mi 49Gi
root@dbserver04-cds:/home/mydbops#

PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND

2916728 mongodb 20 0 64.9g 63.3g 36096 S 68.0 61.4 678:07.12 mongod

Daniele_Tessaro2 · 2024-12-18T17:31:53.026Z

I have a very similar issue, with MongoDB 7.0.14.
I think the culprit in my case is that the one secondary having issues is the only one on Amazon Linux 2023 instead of Amazon Linux 2. I’m wondering if there is some kernel configuration that might have changed.
Did you find anything useful?