I notice that I regularly get an error 520 when I call a page on my site. it only lasts a short time, and it’s 1 in 50 pages where it happens. My site is www.treinenweb.nl and I’m curious if there are any disruptions at Cloudflare or the routes?
I can’t find anything in the error log on my web server that causes this. Web servers just keep running, no errors in the error_log.
Do you know more?
I have made some tests.
With Cloudflare off, there is no problem. (other domain, same source)
In the erro_log i also don’t see any problem.
Can you share the domain name?
Some fix ideas here
See the domainname in the startpost.
I see there’s nothing wrong on my server.
Do you will have a ray-ID?
Anyone have any ideas? In the test environment of my site that runs on the same server, but is not secured via CloudFlare, this does not play. I don’t see any strange things.
So apparently there seems to be something going on with Cloudflare.
Can this be escalated or investigated?
I tested, working and loading fine from my end.
Hm, have you tried clearing your Web browser cache or trying to access your website from another Web browser, or a private window, or even if possible via an VPN connection?
May I ask is the website working over an secured HTTPS connection having the propper and valid SSL certificate (which covers both www and non-www)?
Maybe some packets are being dropped or rejected, somehow?
May I also ask who is your hosting provider?
Maybe some recenty topic could be of help or related to this issue, if it’s the same provider, or maybe maintenance at the datacenter or a switch, etc…
Just to make sure, ss it’s already suggested from above post, may I recommend “just in case” to allow, if already not, Cloudflare to connect to your origin host/server using the instructions as written on the below article?:
https://support.cloudflare.com/hc/en-us/articles/201897700-Allowing-Cloudflare-IP-addresses
Cloudflare IP ranges can be found here:
What result do you get by openning the URL https://www.treinenweb.nl/cdn-cgi/trace/?
Is that specified domain being served and working over an IPv4 or an IPv6 address from your origin host/server?
Yes, it happens in 1 of the 30 á 50 requests. I have this problem on more devices, and at random pages.
So it’s not my cookies. Maybe strange things in my site, but I’ve only recently started to suffer from it, without having changed anything special. I have even restarted by Apache and PHP processes, but it is no solution.
I’ve also already tested it on the same codebase on my test environment that isn’t connected to CloudFlare, and when I surf there for a few minutes, nothing goes wrong.
Also, no load balancers are running, and the (web)server doesn’t give any strange problems in the log either.
Wich details from the trace-URL should i give here? All details?
Anyone an idea?
Hm…
May I ask have you tried writing an e-mail to your hosting provider to check? If so, what would they say about this?
Therefore, you could try writing a ticket and contacting Cloudflare support due to your issue:
In my test environment, on the same code base, but outside of CF, it works fine. No weird error messages, I don’t see any errors, and no things in the logs.
So I don’t see any reason to contact my hosting. I am also the server-manager (B.O.F.H.) server of my virtual server.
The problem started last weekend without me doing anything. So I can’t imagine anything other than CloudFlare having a problem.
I can confirm this. I have the same problem on two Directadmin / Centos 7 servers. Problem started between July 16 and 26. I was on vacation for a week and did not work on the servers or perform updates through Wordpress. A Western European Cloudflare server has a problem somewhere.
Glad to hear I’m not the only one. How did you find out it’s at a CF in western Europe? Does it work from other continents?
Have you created a ticket at the support? Later this day i will do this.
If not, refer to this topic 
How are you determining this? Are you sure nothing is rejecting the requests?
If you think it is an issue with a Cloudflare PoP, please post the colo you get from example.com/cdn-cgi/trace.
Make sure you have RayIDs, Traceroutes and HAR files available to support if you do contact them.
Clicked 50 times fast to get it. Did not open support ticket.
Ray ID: 676e56282abb3b01 • 2021-07-30 11:44:42 UTC
ts=1627645628.147
visit_scheme=https
uag=Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/92.0.4515.115 Safari/537.36
colo=CDG
http=http/3
loc=NL
tls=TLSv1.3
sni=plaintext
warp=off
gateway=off
Ray ID: 676e669489433bd4 • 2021-07-30 11:55:54 UTC
ts=1627646187.185
visit_scheme=https
uag=Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/92.0.4515.107 Safari/537.36 Edg/92.0.902.55
colo=CDG
http=http/3
loc=NL
tls=TLSv1.3
sni=plaintext
warp=off
gateway=off
I would suggest that your server or firewall may be rate limiting or blocking these connections. It’s not impossible, but I doubt it’s an issue in CDG.
I confirm too ! We have some randoms 520 errors since few days, without reason (no update on the website, firewall or anything else).
We analyzed the logs on the server and didn’t see any call/error or firewall blocking when these errors triggered.
We reproduce these 520 approximately every 50 / 60 calls, never on the same pages.
That’s not a problem in CDG only (if it’s a PoP issues) because we reproduced that in Paris and Amsterdam.
I have problems with the colo’s: AMS and FRA.
In both cases is the 520 error random.
I emphasize that nothing is blocked on my server. And I haven’t made any changes to my server in the past period.
Exact same problem here… 520 errors when cloudflare is on, no errors when cloudflare is off.
Happening for days, so far, it does not seem to be a server problem.
any update on this?
I don’t want to be hasty, but today I didn’t get a 520 error after a few minutes of random refresh on various pages.
Would it be solved then?
I keep my fingers crossed! 
I hope someone from CF can tell us more.
