Weird problem which I can't solve

wav3front

Hi all,

For several months now, every now and then (around once per week or so), a website that has a lot of traffic, is almost inaccessible from Athens, Greece (and ONLY from Athens)

This website runs on Enhance, on a 4585PX server hosted in OVH, and reverse proxied via cloudflare. It has quite a lot of traffic, around 50k unique visitors per day.

What happens is this: any user from Athens area (any ISP) is unable to open the website, or opens incredibly slow. This feels like something on network level is throttling the traffic.

I have made several tests, here's some more valuable data:

This happens only in Athens (70% of traffic on that website is from Athens). I have repeatedly tested several other locations, like Sofia, Frankfurt, Stockholm, etc. when this issue occurs, and the website open instantly from any other location. This suggests that this is not a server issue.
Connection from Athens DIRECT to the OVH server shows no issue. Several tests there, like mtr, pings, speed tests etc., everything is fine
So the issue seems to be between Cloudflare and OVH. This makes it hard to find the cause, as any support ticket to Cloudflare is almost useless, as they reply after 1-2 days saying "Everything looks fine" (the issue usually lasts 6-8 hours or so)
OVH support is also useless, they take a long time to reply.
Turning on Cloudflare Argo instantly solved it, but the cost for that bandwidth would be enormous
Switching IPs for the website (OVH IP) temporarily fixes it for a few minutes, and then the issue returns.
Turning off Proxy in Cloudflare immediately solves the issue, but exposing our server IP is not an option.
I have also tried to load-balance the traffic in 3 IPs (on the same server) via Cloudflare Load Balance and it did not help

I have looked over and over at server level for anything that could explain it, for example, since this only happens from Athens via Cloudflare, this could suggest that Cloudflare Athens's IPs could be rate-limited somehow. I have not found any issue on server. CPFence is also installed, and DDoS is set to 5000. Just in case, I uninstalled CPFence and nothing changed, so it's not related to CPFence. Web server is OLS.

Any help here would be greatly appreciated. This is driving us crazy, and we are no close to finding a solution.

Thanks!

cfernandeztrujillo

wav3front We in Chile have been experiencing this issue several times a month with dedicated servers at Hetzner—but not with the cloud services. However, we do get consecutive 520 errors that last for a few hours and then disappear. We experienced slowdowns, and in some cases, websites stopped loading and showed a host error on Cloudflare. This led us to disable the proxy and move the sites to a location in the United States. The problem seems to be related to European routes. What people are saying on Reddit is similar; you can look for more information in the threads created by users about this issue.

adil

I saw a few weeks ago similar issue on Reddit, their issue was caused because CloudFlare had some weird issues with some ISPs, but they said that they tried Argo (https://developers.cloudflare.com/argo-smart-routing) and it seems to help them, You could also try to upgrade that website to the Pro plan.

wav3front

adil do you remember the Reddit thread? Yes, Argo could fix it, but for our bandwidth the Argo cost is $52.000/month (true story)

You could also try to upgrade that website to the Pro plan.

We're actually at Business plan.

cfernandeztrujillo So it was the same issue as ours, but only happened with Dedicated servers and not with Hetnzer Cloud? I cannot understand the reason for this. Do you remember any specific Reddit thread discussing this?

mike We did provide an MTR from our local Athens connection to OVH. There's no way to provide an MTR from Cloudflare reverse proxy to OVH.

gmakhs Unfortunately removing Cloudflare is really our last option. this website has almost 0.5PT of traffic per month.

thank you all for your responces.

mike

its most probably an interchange issue. if you wanna stick with cloudflare try another provider. if you wanna open a ticket with cloudflare provide them with an MTR from a looking glass from athens -> your server

gmakhs

Remove cloudflare, (or buy the 200/m plan) , and improve the website so it works without the need of it, there many ways that can be done

cfernandeztrujillo

wav3front Here you can see some threads discussing this problem; even a website was created about this case.

https://netzbremse.de/

https://www.reddit.com/r/hetzner/comments/1qpg095/is_there_any_problem_with_hetzner_and_cloudflare/

https://www.reddit.com/r/CloudFlare/comments/1os2bax/telekoms_isp_and_cloudflare_very_slow/

https://www.reddit.com/r/CloudFlare/comments/1qiad3y/anyone_having_issues_with_cf_being_slow_in_europe/

https://www.reddit.com/r/CloudFlare/comments/1peaev4/whats_going_on_with_cloudflare_all_my_websites/

wav3front

I found a post on Cloudflare Community suggesting that this may be related to HTTP/3 (with QUIC). I turned this off.

I'm surprised that there are so many reports for this and it continues.

wav3front

I've found another post suggesting the same (problem is with HTTP/3-Quic.

wav3front

cfernandeztrujillo wow. This is bigger than I thought.
I guess I'll move my server outside of Germany.