Solved: WARNING: The TCP backlog setting of 511 cannot be enforced because /proc/sys/net/core/somaxconn is set to the lower value of 128.

[kevin201]

I spent some time researching this on line before I found the solution in my case.

After changing the host machine's net.core.somaxconn value in vain (sudo sysctl -w net.core.somaxconn=1024;sudo sysctl -p, add "net.core.somaxconn=1024" to /etc/sysctl.conf)

I found this, added to the redis section of the docker-compose.yml:

sysctls:
      - net.core.somaxconn=1024

Check it with:

$ docker exec immich_redis sysctl net.core.somaxconn
net.core.somaxconn = 1024

Hope this helps someone avoid the same wild goose chase I went on.