NODEBB: Nginx error performance & High CPU

[phenomlab]

@DownPW I’ve just started reviewing your nginx.log and a couple of things immediately stand out for me

1. Literally all of the IP addresses are within Cloudflare’s subnet ranges. This means that you cannot possibly tell if the traffic is legitimate or not as you do not know what the originating IP addresses are
2. The TCP established times are all within seconds of each other but from different IP addresses. This very much lends itself towards the traffic not being organic in my view, but you will never really know the true identity of these connections without first attempting to unpack the TCP headers - see the below

https://support.cloudflare.com/hc/en-us/articles/200170786-Restoring-original-visitor-IPs

You could temporarily disable Cloudflare on your site to get a quick analysis, then keep an eye on your own DDoS implementation to determine if this traffic is legitimate or not.

The bottom line is this. Don’t be lulled into a false sense of security just because Cloudflare passes the traffic to your site.

[DownPW]

@phenomlab

I don’t understand all you say.
Finally what we can do ?

Actually we have 1.1k users online

We have a lot of inscriptions

[DownPW]

@phenomlab 362 user inscription in two days and many user on just read forum

[phenomlab]

@DownPW said in NODEBB: Nginx error performance & High CPU:

I don’t understand all you say.
Finally what we can do ?

My point here is that the traffic, whilst legitimate in the sense that it’s from another site that has closed, could still be nefarious in nature so you should keep your guard up. However, a number of signups can’t be wrong - particularly if they are actually posting content and not performing requests that actually do not pertain to available URL’s on your site.

I see no indication of that, so the comfort level in the sense that it’s legitimate traffic does increase somewhat accompanied by the seemingly legitimate registrations. However, because all the source IP addresses and within the Cloudflare ranges, you have no ability to tell really who they are without performing the steps I outlined in the previous post.

The good news is that your site just got a huge increase in popularity, but with that will always be a need to keep a close eye on activity. It would only take one nefarious actor to potentially bring down your site.

The nginx configuration you’ve applied will indeed alleviate the stress placed on the server but is a double edged sword in the sense that it does make the goalpost much wider in terms of any potential attack.

My advice herein would be to not scale these settings too high. Use sane judgement.

For the NodeBB side, I know they have baked rate limiting into the product but I’m sure you can actually change that behaviour.

Have a look at

/admin/settings/advanced#traffic-management

You’ll probably need to play with the values here to get a decent balance, but this is where I’d start.

[DownPW]

@phenomlab

I think you’re right Mark and that’s why I come here looking for your valuable advice and expertise

Basically, the illegal site that closed was a movie download site A topic was opened on our forum to talk about it and many came looking for answers on why and how.

You’re actually right about the fact that we can’t be sure of anything and there are bot attacks or ddos in the lot of connexions

I activated the under attack mode on Cloudflare as you advised me to see (just now.) and we will see like you said

As you advised, I also reset the default nginx configuration values ​​and removed my nginx modifications specified above.

I would like to take advantage of your expertise, see a hand from you to properly configure nginx for ddos ​​and high traffic. (What precise modifications to specify as well as the precise values.)

[phenomlab]

@DownPW ok, good. Let’s see what the challenge does to the site traffic. Those whom are legitimate users won’t mind having to perform a one time additional authentication step, but bots of course will simply stumble at this hurdle.

[DownPW]

@phenomlab

number of user is better (408) but a lot of loose connexion. navigation is hard

[DownPW]

I have chaneg nginx conf with :

worker_rlimit_nofile 70000;

events {
worker_connections 65535;
multi_accept on;
}

CF is under attack mode

[phenomlab]

@DownPW I still have access to your Cloudflare tenant so will have a look shortly.

EDIT: I am in now - personally, I would also enable this (and configure it)

[DownPW]

@phenomlab I have already activate it and add a waf rules for russian country

With this bots settings :

and this settings for ddos protection :

[phenomlab]

@DownPW said in NODEBB: Nginx error performance & High CPU:

I have already activate it

Are you sure? When I checked your tenant it wasn’t active - it’s from where I took the screenshot

[DownPW]

@phenomlab

yep I activate it after

[DownPW]

For your information @phenomlab ,

• I have ban via iptables suspicious ip address find on /etc/nginx/accesss.log and virtualhost access.log like this : iptables -I INPUT -s IPADDRESS -j DROP
• Activate bot option on CF
• Create contry rules (Russie and China) on CF WAF
• I left under attack mode option activated on CF
• I have just change nginx.conf like this for test (If you have best value, I take it ! ) :

worker_rlimit_nofile 70000; 

events {

	worker_connections 65535;
	multi_accept on; 
}

http {

	##
	# Basic Settings
	##

	limit_req_zone $binary_remote_addr zone=flood:10m rate=100r/s; 
	limit_req zone=flood burst=100 nodelay; 
	limit_conn_zone $binary_remote_addr zone=ddos:10m; 
	limit_conn ddos 100;

100r/s iit’s already a lot !!

and for vhost file :

server {
	.....

        location / {
				
				limit_req zone=flood; #Test 
				limit_conn ddos 100; #Test 
}

–> If you have other ideas, I’m interested
–> If you have better values ​​to use in what I modified, please let me know.

[phenomlab]

@DownPW my only preference would be to not set worker_connections so high

[DownPW]

@phenomlab

Ok so what value do you advise?

[phenomlab]

@DownPW you should base it on the output of ulimit - see below

https://linuxhint.com/what-are-worker-connections-nginx/#:~:text=The worker_connections are the maximum,to accommodate a higher value

With that high value you run the risk of overwhelming your server.

[DownPW]

@phenomlab

Thanks mark

My ulimit is 1024, so I will set it to 1024

[phenomlab]

@DownPW And the worker_processes value ? I expect this to be between 1 and 4 ?

[DownPW]

@phenomlab

worker_processes auto;

[phenomlab]

@DownPW ok. You should refer to that some article I previously provided. You can probably set this to a static value.