For the past several weeks, I have been working with Joomla in a clustered environment. We have a single load-balancer running HAProxy that sends requests to two web servers synchronized with unison. One server is a hybrid and includes both the MySQL database as well as Apache2/PHP5. The other web server is strictly Apache2/PHP5. We have been renting two super fast dedicated servers temporarily until we acquire some new hardware, so I had to make do with what few servers I had.
Update: Having written this blog post almost a full year ago, I have since then completely switched all of my Joomla websites to the automatically scaling website cloud host: Scale My Site. Since doing so, we haven’t had to deal with HAProxy, load balancing, or anything with regard to scaling due to the hosting cloud’s seamlessly clustered environment. I highly recommend anyone reading this article right now to check out cloud hosting to get load balancing/scaling for your Joomla website without breaking a sweat.
The load balancer is located at our own colo. I followed the tutorial on Setting Up A High-Availability Load Balancer (With Failover and Session Support) With HAProxy/Heartbeat On Debian Etch to set up two servers at our colo in an ActivePassive fashion using Heartbeat for redundancy.
Weighted Load Balancing
Since I’m using only two web servers and one needs to serve database requests, I decided to set weights in HAProxy so that the hybrid server receives half as many requests as the dedicated web server. Here is an example of what my haproxy.cfg file contains:
global log 127.0.0.1 local0 log 127.0.0.1 local1 notice maxconn 4096 user haproxy group haproxy defaults log global mode http option httplog option dontlognull retries 3 redispatch maxconn 2000 contimeout 5000 clitimeout 50000 srvtimeout 50000 listen webfarm 220.127.116.11:80 mode http balance roundrobin cookie SERVERID insert nocache indirect option forwardfor option httpchk HEAD /check.txt HTTP/1.0 # Stats stats enable stats auth admin:password # Web Node server SBNode1 18.104.22.168:80 cookie Server1 weight 20 check # Web + MySQL Node server SBNode2 22.214.171.124:80 cookie Server2 weight 10 check
How to Use the Administrator Control Panel in a Joomla Cluster
Many people understand that it’s a super big pain to work with the administrator control panel in a Joomla clustered environment. First of all, you’ll keep getting kicked out every few page requests, even while using sticky/persistent load balancing. Second, working with backend WYSIWYG rich-text editors is nearly impossible. I figured out how to do it, and here’s what I did.
- Decide upon the management node
- Give the management node a public host entry in DNS (e.g. node1.yourdomain.com)
- Open configuration.php for editing
- Locate the “live site” variable ($mosConfig_live_site)
- Replace with “http://” . $_SERVER[“HTTP_HOST”];
Using the current host as the live site allows you to use node1.yourdomain.com as an access point for the control panel. You can work in the control panel without doing this, but you will run into tons of problems with rich-text editors and custom components that request the live site URL in their underlying code.
Update: Recently, I implemented a load balancing solution using HAProxy that used the ACL system to send all traffic with /administrator/ in the URL to one “master” node, and it provided a way around the Joomla configuration change mentioned above. Check out this blog post for more info.