Reverse proxy setup on haproxy gives 500; wget on base server & nginx works - reverse-proxy

Question

I am trying to setup haproxy as a reverse proxy for a server. I am on Centos.
The config goes like this:
global
#log /dev/log local0
#log /dev/log local1 notice
log 127.0.0.1 local2 info
log 127.0.0.1 local2 notice
log 127.0.0.1 local2 debug
chroot /var/lib/haproxy
stats timeout 30s
user haproxy
group haproxy
daemon
defaults
mode http
log global
option httplog
option dontlognull
option http-server-close
option forwardfor except 127.0.0.0/8
option redispatch
retries 3
timeout http-request 10s
timeout queue 1m
timeout connect 10s
timeout client 1m
timeout server 1m
timeout http-keep-alive 10s
timeout check 10s
maxconn 3000
frontend http_front
bind *:801
option forwardfor
stats enable
default_backend http_back
backend http_back
mode http
option httpchk
option forwardfor
http-send-name-header Host
balance roundrobin
server server1 stg-hostserv.com:80
But, if I do a wget against it, I am getting the below error.
# wget http://0.0.0.0:801
--2018-07-16 14:26:24-- http://0.0.0.0:801/
Connecting to 0.0.0.0:801... connected.
HTTP request sent, awaiting response... 500 Internal Server Error
2018-07-16 14:26:24 ERROR 500: Internal Server Error.
haproxy -f /etc/haproxy/haproxy.cfg -d
[WARNING] 197/200148 (13833) : config : frontend 'GLOBAL' has no 'bind' directive. Please declare it as a backend if this was intended.
Available polling systems :
epoll : pref=300, test result OK
poll : pref=200, test result OK
select : pref=150, test result FAILED
Total: 3 (2 usable), will use epoll.
Using epoll() as the polling mechanism.
00000000:http_front.accept(0004)=0006 from [127.0.0.1:60696]
00000000:http_front.clireq[0006:ffffffff]: GET / HTTP/1.1
00000000:http_front.clihdr[0006:ffffffff]: User-Agent: Wget/1.14 (linux-gnu)
00000000:http_front.clihdr[0006:ffffffff]: Accept: */*
00000000:http_front.clihdr[0006:ffffffff]: Host: 0.0.0.0:801
00000000:http_front.clihdr[0006:ffffffff]: Connection: Keep-Alive
00000000:http_back.srvrep[0006:0007]: HTTP/1.1 500 Internal Server Error
00000000:http_back.srvhdr[0006:0007]: Content-Type: text/html
00000000:http_back.srvhdr[0006:0007]: Server: Microsoft-IIS/8.0
00000000:http_back.srvhdr[0006:0007]: X-Powered-By: ASP.NET
00000000:http_back.srvhdr[0006:0007]: Date: Tue, 17 Jul 2018 12:02:00 GMT
00000000:http_back.srvhdr[0006:0007]: Connection: close
00000000:http_back.srvhdr[0006:0007]: Content-Length: 1208
00000001:http_front.clicls[0006:ffffffff]
00000001:http_front.closed[0006:ffffffff]
^C
[root#izp0w3tkx2yr8zhes26ajqz ~]#
I tried different config for the server and consistently hit 500 error. Wget to the base server works without any issues.
I setup nginix to the same thing and it works beautifully. Just haproxy does not seem to work. The customer wants it on haproxy. :)
Can you please advise where I can look at to further debug. Appreciate your assistance.

Answer 1

This update from nuster cache server helped solve the problem:
Does your backend Microsoft-IIS/8.0 check host header? as you set http-send-name-header Host, so request from HAProxy to stg-hostserv.com:80 looks like GET / HTTP/1.1 Host: izp0w3tkx2yr8zhes26ajqz
HAProxy worked when I set:
http-request set-header Host stg-hostserv.com