frontend webserver
        bind    :80
        mode    http
        acl is_www hdr_beg(host) -i     www.domain.com
        use_backend http_cluster if is_www
        default_backend http_redir

backend http_redir
        mode    http 
        balance source
        option  nolinger
        server  web 127.0.0.1:8080 redir http://www.domain.com

backend http_cluster
        mode    http
        option  forwardfor
        balance source
        option  httpclose
        option  httpchk HEAD / HTTP/1.0
        server  web01 172.16.0.11:80 weight 1 check inter 1000 rise 5 fall 1
        server  web02 172.16.0.12:80 weight 1 check inter 1000 rise 5 fall 1
        server  web03 172.16.0.13:80 weight 1 check inter 1000 rise 5 fall 1
        server  web04 172.16.0.14:80 weight 1 check inter 1000 rise 5 fall 1

In this example:

*rewrite urls from domain.com to www.domain.com*

This is somewhat documented elsewhere, but not very well, so here's an example on how to perform simple URL rewriting with HAProxy (instead of using mod_rewrite with apache).

This works great if your servers use lighttpd, nginx, or anything that doesnt provide its own simple url rewriting.

HAProxy URL Rewriting

url, apache

Apache