When I started with Fly had some 525 issues too. Issues are related to SSL/TLS, more info also: Troubleshooting SSL errors – Cloudflare Help Center
To resolve the issues I am:
- Running CloudFlare SSL/TLS in full mode (*)
- Setup Fly to not terminate TLS at the edge
(*) Generated an origin certificate in CloudFlare for the host. It is used for all connections that come from CloudFlare.
I did notice that sometimes during a deploy CloudFlare shows a 525. The 525 happens when CloudFlare is trying to make requests to the app during the time it’s being re-started, the 525 doesn’t go away immediately when the instance comes online think CloudFlare uses a delay and requires multiple successful health checks on their end before this happens.
When running 2 instances of the app using the default canary deploy I have not experienced this issue.
Hope this helps.
@kurt Declaring CloudFlare persona none grata would be bummer. We make heavy use of CloudFlare workers for about anything and everything.