Well, overnight the site went down, so I'm back at the drawing board to see (1) what is the specific bottleneck and (2 how to fix it.

I asked GPT what are the memory requirements for (1) mysql and (2) a drupal site, the two memory-intensive things I'm running in this system. It said, I should be okay with 4Gb of RAM. As I expected.

I adjusted mysql config but it didn't help: https://github.com/wasya-co/docker_drupal/blob/0.0.0/docker-compose.yml-template#L36 

I have the fortune and the misfortune of having to scale my Drupal site immediately. It's getting more traffic than I can currently accommodate - and so the next scaling steps have to be taken.

For testing ansible roles, I need a docker container that runs systemd or init - a container in which services can be enabled. I also need this container to be accessible via ssh. This way, I don't have to spin up cloud resources (which are not free) in order to test doing something on a remote.

Molecule is a testing framework designed for Ansible roles, collections, and playbooks. In the Ansible ecosystem, it provides a structured workflow to develop and verify infrastructure as code. 

This is an example of setting up a NAT inside docker - in a fairly self-explanatory and minimal way. There are three examples that you can run in this setup: a positive example, a negative example, and a chatty positive example for debugging and demonstration purposes.

Running this worked for me:

 mysqlcheck --repair --all-databases

You may need to add your credentials and hostname to the command.