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, running on GCE), where the default number of open files is set to 1000, I usually just set the ulimit to the desired number (64,000).

This works out great, except that when I dockerized my application and deployed it - I found out that docker kind of ignores the limit definitions. I have tried the following (all on the host machine, not on the container itself):

MAX=64000
sudo bash -c "echo \"* soft nofile $MAX\" >> /etc/security/limits.conf"
sudo bash -c "echo \"* hard nofile $MAX\" >> /etc/security/limits.conf"
sudo bash -c "echo \"ulimit -c $MAX\" >>  /etc/profile"
ulimit -c $MAX

After doing some research I found that people were able to solve a similar issue by doing this:

sudo bash -c "echo \"limit nofile 262144 262144\" >> /etc/init/docker.conf"

and rebooting / restarting the docker service.

However, all of the above fail: I am getting the "too many open files" error when my app runs inside the container (doing the following without docker solves the problem).

I have tried to run ulimit -a inside the container to get an indication if the ulimit setup worked, but doing so throws an error about ulimit not being an executable that's a part of the PATH.

Anyone ran into this and/or can suggest a way to get docker to recognzie the limits?

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>