so we want a HA setup with external database
snap install is a good way to go,
however, it doesn’t allow us to specify database port to use, and since snap app is running on read only fs, I have to do some mount trick like
sudo mount --bind -o nodev,ro /tmp/maas-config.py /snap/maas/current/lib/python3.6/site-packages/maasserver/config.py to make it work.
But it will broken if I update snap app.