defaults
    log global
    mode http
    option httplog
    timeout connect 5s
    timeout client 30s
    timeout server 30s

frontend fe_http
    bind :80
    acl host_app req.hdr(host) -i app.example.com www.app.example.com
    acl host_api req.hdr(host) -i api.example.com
    use_backend be_app if host_app
    use_backend be_api if host_api
    default_backend be_default

backend be_app
    mode http
    balance roundrobin
    server app1 10.0.20.11:8080 check
    server app2 10.0.20.12:8080 check

backend be_api
    mode http
    balance roundrobin
    server api1 10.0.20.21:8080 check

backend be_default
    mode http
    server fallback1 10.0.20.31:8080 check