A 520 error occurs when the connection started on the origin web server, but that the request was not completed. The most common reason why this would occur is that either a program, cron job, or resource is taking up more resources than it should causing the server not to be able to respond to all requests properly.
Review the Quick Fix Ideas in this Community Tip for troubleshooting suggestions.
All Cloudflare ip addresses have been white listed (we have had this setting for 1.5 years now). we also checked if there has been any changes to the ip list from Cloudflare and there is none (ipv4 and v6).
I can confirm we get http 200s when we bypass Cloudflare (e.g. accessing via the load balancer DNS directly). all requests are served with normal speed. (the home page of the website makes 100+ API calls)
I will test making changes to Cloudflare setting (e.g. pause) in the next 2 hours (once our DevOps is online).
Are you aware of any widespread issues with Cloudflare across any specific regions ? if not then this is probably specific to our site and perhaps some Cloudflare setting.
I would suggest you still contact support and ask, providing any info such as connection IDs as you can as they should be able to look into it and provide more info/help with what could have caused this. Not seen anything indicating an issue with Cloudflare at the moment or earlier…
We are experiencing this with BlueHost and after all the same tests above they conclude that it is Cloudflare that is at fault. We have bypassed the firewall, cleared the cache and still getting 520 errors. Interestingly enough the server is not recording any off the 500 errors which led us to find this post. If you guys find a solution quickly please let us know.