Problem:

If a newly created docker container is showing a server error:

Check /edx/var/log/supervisor/lmstderr.log

If you see the error:

OperationalError: (2002, "Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)")

Look for the file: /var/run/mysqld/mysqld.sock

If that socket file doesn’t exist, the server probably ran out of file descriptors.

The Fix:

On the server, run: 

sudo sysctl fs.aio-max-nr=262144

Making the change persist across reboots:

Edit the file: sudo vi /etc/sysctl.conf

And add the line:

fs.aio-max-nr=262144