Docker Ignores limits.conf (trying to solve “too many open files” error)

Question

I\'m running a web server that is handling many thousands of concurrent web socket connections. For this to be possible, on Debian linux (my base image is google/debian:wheezy,

Answer 1

I was able to mitgiate this issue with the following configuration :

I used ubuntu 14.04 linux for the docker machine and the host machine.

On the host machine You need to :

• update the /etc/security/limits.conf to include :* - nofile 64000
• add to your /etc/sysctl.conf : fs.file-max = 64000
• restart sysctl : sudo sysctl -p

Answer 2

You can pass the limit as argument while running the container. That way you don't have to modify host's limits and give too much power to the container. Here is how:

docker run --ulimit nofile=5000:5000 <image-tag>

Answer 3

With docker-compose you could configure ulimits.

https://docs.docker.com/compose/compose-file/#ulimits

You can add soft/hard limits as a mapping.

ulimits:
  nproc: 65535
  nofile:
    soft: 20000
    hard: 40000

Although not ideal you could run container with privileged option (Mostly for a quick non-optimal solution for a Dev environment, not recommended if security is a concern).

docker run --privileged

Please see:

https://docs.docker.com/engine/reference/run/#runtime-privilege-and-linux-capabilities