Today I decided to turn on HAProxy to load-balance between Apache instances running Phusion Passenger on two separate machines. The results are clear. Doing this nearly doubled our ApacheBench throughput scores.

This config was adaped from the 37Signals blog post here.

# /etc/haproxy/haproxy.cfg
global
        maxconn 4096

defaults
        mode    http
        retries 3
        option redispatch
        maxconn 2000
        contimeout	5000
        clitimeout	50000
        srvtimeout	50000

listen web1 XXX.XXX.XXX.210:80
       mode http
       balance roundrobin
       server web1 XXX.XXX.XXX.210:8080
       server web2 XXX.XXX.XXX.211:8080

Passenger is configured the normal way.

<VirtualHost *:8080>
        ServerName www.example.com
        DocumentRoot /var/www/rails_project/current/public
</VirtualHost>