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2026-02-25 Finetuning MongoDB serveur#

As mongo does not seems to be so active on the new scaleway server, I was asking myself if some optimizations needs to be done.

Adding memory#

I added some memory to MongoDB wiredtiger cache from 32G to 64G.

This gave this PR: https://github.com/openfoodfacts/openfoodfacts-shared-services/pull/31

Fixing some kernel settings#

Logging in mongo I saw those messages: 

# sudo -u off docker compose exec mongodb mongo
...
---
The server generated these startup warnings when booting: 
        2026-02-25T15:57:57.890+00:00: Access control is not enabled for the database. Read and write access to data and configuration is unrestricted
        2026-02-25T15:57:57.891+00:00: /sys/kernel/mm/transparent_hugepage/enabled is 'always'. We suggest setting it to 'never'
        2026-02-25T15:57:57.891+00:00: Soft rlimits too low
        2026-02-25T15:57:57.891+00:00:         currentValue: 1024
        2026-02-25T15:57:57.891+00:00:         recommendedMinimum: 64000
---
>

So I decided to fix it.

Fixing hugepage#

I did: 

cat never > /sys/kernel/mm/transparent_hugepage/enabled
but it won't survive a reboot,

  • so I edited /etc/default/grub to add: transparent_hugepage=never in GRUB_CMDLINE_LINUX
  • and then recreate grub config. issuing: update-grub

Fixing rlimits#

This is at the docker compose level. We can see

  • that indeed default soft limits are thight, using ulimit -a -S
  • but that open files hard limit is high, using ulimit -a -H so we just have to set the right limit for our docker container, thanks to the ulimits section. (use man getrlimit to understand possible values. instead of RLIMIT_NOFILE, simply use nofile)

To verify our docker compose config works, we can start the container, use docker compose exce mongodb bash -c "ulimit -a" to see limits.

This gave this PR: https://github.com/openfoodfacts/openfoodfacts-shared-services/pull/32