How to redirect to multiple servers sitting behind HAProxy which have different path begining

I have 3 servers which listen on following port ,

> 10.21.5.39:80    -->   api.something.com
> 10.21.4.234:80    -->   *.something.com
> 10.21.5.73:80     -->   coolapi.something.com
> 10.21.5.73:3002    -->   school.something.com

I am using a HAProxy server to redirect the traffic to these backends, i am using the following config on haproxy which doesn't seem to workout.

frontend api
       bind *:80
       acl url_api path_beg /api
       use_backend api-backend if url_api

frontend custui
       bind *:80
       acl url_custui path_beg *
       use_backend custui-backend if url_custui


frontend backoffice
       bind *:80
       acl url_backoffice path_beg /backoffice
       use_backend backoff-backend if url_backoffice

frontend partnerui
       bind *:80
       acl url_partnerui path_beg /partner
       use_backend partner-backend if url_partnerui


backend api-backend
    mode    http
    option  httpchk
    server  api01 10.21.5.39:80

backend custui-backend
    mode    http
    option  httpchk
    server  custui01 10.21.4.234:80

backend backoff-backend
    mode http
    option httpchk
    server backoff01 10.21.5.73:80


backend partner-backend
    mode http
    option httpchk
    server backoff01 10.21.5.73:3002

So the idea is to let HAProxy listen on 80 and then redirect to the backends listening on the specified port.. Please help

Solution

A couple of issues:

You have multiple frontends all listening on port 80; I would recommend having a single frontend and using ACLs to direct traffic to your backends. From the HAProxy documentation:

There may be as many "use_backend" rules as desired. All of these rules are evaluated in their declaration order, and the first one which matches will assign the backend.
You provide option httpchk, but do not have any support for checks on your server lines; from the HAProxy documentation (1.5.18 specifically, but comparable for other versions)

The port and interval are specified in the server configuration.

I would recommend adding an interval (in ms), such as
```
server  custui01 10.21.4.234:80 check inter 2000
```
You are specifying mode http and option httpchk in each backend; these can be combined in the defaults section and then overridden in a backend if necessary.
I like using hdr(host) to check for the HTTP request's URL, so I would rewrite acl url_api path_beg /api as acl url_api hdr(host) -m beg api., but that is down to personal preference

Combining those recommendations with your listed requirements, here is an updated version of your configuration file:

defaults
   mode    http
   option  httpchk

frontend something.com
   bind *:80

   acl url_api path_beg /api
   use_backend api-backend if url_api

   acl url_backoffice path_beg /backoffice
   use_backend backoff-backend if url_backoffice

   acl url_partnerui path_beg /partner
   use_backend partner-backend if url_partnerui

   # Catches anything not covered by use_backend above
   default_backend custui-backend

backend api-backend
    server  api01    10.21.5.39:80   check inter 2000

backend backoff-backend
    server backoff01 10.21.5.73:80   check inter 2000

backend partner-backend
    server backoff01 10.21.5.73:3002 check inter 2000

backend custui-backend
    server  custui01 10.21.4.234:80  check inter 2000