Setting Custom Header on a per server basis in HAProxy

Question

I need to load balance 3rd party services using HAProxy 1.7. Each of the servers requires unique Basic Auth Headers. I am looking for an approach similar to this below, where I can "roundrobin" between backend servers, but each server needs a different HTTP header:

frontend http-in
    bind *:80
    use_backend servs

backend servs
    reqidel '^Authorization:.*'
    reqadd 'Authorization: Basic blahblahblah'
    server url1 asdf.example.com:8080 check ssl verify none
    reqidel '^Authorization:.*'
    reqadd 'Authorization: Basic blah2blah2blah2'
    server url2 asdf.example.com:8081 check ssl verify none

This approach only ever uses the first server (url1).

Its how to roundrobin between the two servers, but setting the "Authorization" header to different values for each server. — Flash
Take a look at the hdr() function. It's not exactly what you want but it's a start. It might even be sufficient if you can use for example a second, dummy header. — Mars
What I am need of is a conditional statement that I can apply to each server. Similar to ACLs, but applied individually to each server in a round-robin backend. I have not come across this type of solution, so it may not be possible as I have imagined the solution. — Flash
Can you send another custom header? Then you can route to the correct server using hdr(). So let's say you create 2 additional custom headers and one of them would be intended for server 1 and the other for server 2. The Authorization header can be coupled with these additional headers. — Mars

Flash Flash · Accepted Answer · 2017-03-08T19:08:10

I implemented the following solution to allow for custom headers for each server being load balanced.

frontend http-in
    bind *:80
    use_backend proxy

backend proxy
    balance roundrobin
    server url1-proxy 0.0.0.0:8080
    server url2-proxy 0.0.0.0:8081

listen url1-proxy
    bind *:8080
    reqidel '^Authorization:.*'
    reqadd 'Authorization: Basic blahblahblah'
    server url1 asdf.example.com:8080 check ssl verify none

listen url2-proxy
    bind *:8081
    reqidel '^Authorization:.*'
    reqadd 'Authorization: Basic blah2blah2blah2'
    server url2 asdf.example.com:8081 check ssl verify none

Setting Custom Header on a per server basis in HAProxy

1 Answers