I started the migration of databases to try to avoid the crashing that's been happening.

When I did the test (this), I made a container with the database, using a host network adapter. I then connected to it and the old database with the database tool, and then ran the migration wizard. I recreated the user, and then started monkeying with the configurations to make it use the right host. That went pretty smoothly.

Today (I didn't get to it over the weekend like I'd hoped) I did the same to the largest database, and that seems to also work. Its got a web interface that I haven't taken the time to make work yet, so I added that to my (not so) short list of things to fix.

I then dug into a more concentrated site. Another blog like this one, there's a container with the software which access the database outside the container. I got the idea to tap this up in a Docker Compose and isolate them in a private space. I first created a database container, like the others, and copied the data and created the user. Then I destroyed that container, but left the volume, and then made the compose use the same container. I struggled for too long trying to get the Compose networking working. I couldn't get the web app to participate in both the isolated Compose network with the database, and the existing Docker bridge network that the egress container uses to reverse proxy to the other containers. It seems that although that's a general network, it isn't available for Compose to use in conjunction with other networks. I settled on making both containers use that bridge network, and then used a link to let the one find the other. It also works, although only about 90% the way I'd like it to.

I had a little trouble in the middle, too, as I'd made the user with permissions based on the host network, which is how it is elsewhere, so I had to remember how to do that from the command line to fix it. Once done, the web app container could access the database container and all works well.

I'm trying to think of a way to transition the data to the container databases without having to do the network shuffle, but I'm OK if I have to do the double-clutch. That's a beauty of the containers; they take nothing to get running.