Send real Host header for httpchk in HAProxy

Question

I'm trying to make http (layer 7) checks to monitor backend state in HAProxy load balancer. I have 3 backends configured, each having it's own name. Current configuration looks like this:

backend apiservers
  balance                 leastconn
  mode                    http
  option                  httpchk GET /healthz HTTP/1.0\r\nAuthorization:\ Bearer\ SOME_TOKEN_HERE
  http-check              disable-on-404
  http-check              expect rstring ^ok
  server                  core1 core1.cloud:443 ssl check
  server                  core2 core2.cloud:443 ssl check
  server                  core3 core3.cloud:443 ssl check

The problem is I can't switch to HTTP/1.1 because I wasn't able to find a way to pass a real Host header with httpchk requests. Using some random dummy Host string may cause problems in the feature, so I need to pass the corresponding backend hostname to the Host header. Options like http-request add-header Host %[src] and http-send-name-header Host in the backend section seem not affect httpchk mechanism. Any ideas?

jmoney jmoney · Accepted Answer · 2018-12-11T05:30:24

Updated thanks to borellini.

Per the haproxy docs you can configure the header in the httpchk line. The example from the docs is:

# check HTTP and HTTPs services on a server.
# first open port 80 thanks to server line port directive, then
# tcp-check opens port 443, ciphered and run a request on it:
option httpchk

http-check connect
http-check send meth GET uri / ver HTTP/1.1 hdr host haproxy.1wt.eu
http-check expect status 200-399
http-check connect port 443 ssl sni haproxy.1wt.eu
http-check send meth GET uri / ver HTTP/1.1 hdr host haproxy.1wt.eu
http-check expect status 200-399

server www 10.0.0.1 check port 80

You should then be able to replace the host value with your variable and have it sent.

Send real Host header for httpchk in HAProxy

1 Answers