OK, I figured out how to do this. Upgrade to toolforge 5.3.0 and copy https://gitlab.wikimedia.org/toolforge-repos/rust-hello-world/-/merge_requests/2/

looks nice, but I'm handling multiple wikis, so I would need a different connection string per wiki, which means that pool code wouldn't work, right?

yes, hmmm, 🤔

I guess we need a custom pool type that:

• Loads your replica.my.cnf at startup
• When you ask for a connection, you give it the database name, it gives you a connection
• When returning the connection, if something is waiting for that name it can pass the connection back, otherwise terminate it?
• Bonus points for knowing which databases are on the same server, and can be re-used by issuing a USE <database> command instead of opening a new connection.

AFAICT mysql_async's Pool doesn't mandate connections being made for a single database (we can just specify no database), it's just that we need a way to route them to specific servers

Here's the direction I'm currently going in: https://gitlab.wikimedia.org/repos/mwbot-rs/toolforge/-/merge_requests/1/diffs

If you want to try the WikiPool type in https://gitlab.wikimedia.org/repos/mwbot-rs/toolforge/-/merge_requests/1/, it should be in a mostly working state.