A 522 error occurs because CloudFlare could not make a TCP connection to your origin server before the attempts timed out. This means that CloudFlare was unable to send the HTTP request to the origin because a network connection to the origin server could be established.
This problem may happen for various reasons:
- Rate limiting incoming connections from CloudFlare's IPs.
- A process on the webserver is consuming all of one or more resources at the origin.
- The domain is on a shared hosting platform where traffic or tasks for a separate domain on the same server is taking up one or more resources.
- Network connectivity issues between CloudFlare and the origin web server.
Checking for these conditions with your server administrator or hosting provider is the best way to resolve these errors. If there is a network problem, a traceroute to the origin can be useful.
While the above reasons are the most common, they are not the only reasons why a 522 might be returned when attempting to access your domain.
If you continue to see 522 errors after ruling out the aforementioned possibilities, contact CloudFlare Support for further investigation.