Today, like the past few days, we have had some downtime. Apparently some script kids are enjoying themselves by targeting our server (and others). Sorry for the inconvenience.
Most of these 'attacks' are targeted at the database, but some are more ddos-like and can be mitigated by using a CDN.
Some other Lemmy servers are using Cloudflare, so we know that works. Therefore we have chosen Cloudflare as CDN / DDOS protection platform for now. We will look into other options, but we needed something to be implemented asap.
For the other attacks, we are using them to investigate and implement measures like rate limiting etc.
In case you haven't considered this, some helpful advice.
To keep them from the lemmy.world door after the CDN installation
Change the public IP addresses
rotate your certificates
block all traffic appart from the CDN and only allow a limited known good IP addresses (like yours and your support team).
These steps will make your server harder to find, hopefully they move on.
You might have Cloudflare add a request header to the origin request, like x-cloudflare-key: <somesecret>, and then configure nginx on the server to block everything not containing that header.