HAProxy high connection resets using proxy protocol (no replies)

I’ve been spending the better part of a few days trying to figure this out
but have not made much progress and would greatly appreciate some help.

*System*: Ubuntu Server 16.04.3 LTS, HAProxy 1.7.9, Nginx 1.10.3

*Issue*: Under load or spike in traffic, around 10k/sec non-ssl or 4k/sec
ssl using *proxy protocol*, I get random connection resets (see image as
reported by haproxy). It can be around 10% or so.

[image: 2017-09-02_8-29-35]
2017-09-02_8-29-35.png2259x206 37.1 KB

*Reproducing/Troubleshooting*: I’m able to reproduce the issue every time
load testing using the proxy protocol for example:

- Sending proxy protocol from HAProxy to Nginx, without SSL, I start
getting connection resets at around 10k/sec, all the responses are under
1.5 seconds
- Without the proxy protocol and the same setup I get no errors at all,
to give you an idea at 25k/sec I see no issues
- If I use “mode http” instead of “mode tcp” but still use the proxy
protocol for the HAProxy backend then the issue disappears, however since I
plan to terminate SSL at nginx that is not a solution.
- If I enable SSL (terminated at Nginx) I see the same issue but around
4k/sec and the number of connection resets is much higher around 10%.
- If I disable proxy protocol but still have SSL (terminated at Nginx)
then the issue disappears

My connection timeouts are set to the following, however I don’t think it
is related to this as the responses are all under 1.5 seconds.

timeout connect 10s
timeout client 50s
timeout server 50s

Let me know what could help and I will provide it.