Balancing your requests

Now that we've built it and sure enough, somebody came. Websites may be knocked down to its knees when it became popular enough. But what's the breaking point? With zope, that's not really a problem.

Zope nowadays come with ZEO. ZEO scales zope across multiple boxes. It's really that easy. Build a box, install zope, change zope.conf, and voila, we have ourselves a ZEO Client. And this client share the same ZODB.

But how do we balance the requests to the zeo clients?

There are many ways:

• dig deep into your pocket and buy commercial load balancer; cisco have one, alteon , and may others
• for not too loaded sites, balance might do the job
• there's also LVS, and many tools based on LVS; piranha (if it's still available), eddie, keepalived

I've used piranha since 2000. It's been great. But it's not actively developed now. Or if it is, then I'm probably missing something.

Now, I use keepalived in front of zope sites. Keepalived is a load balancer, HA and notifier, all in one.

Installing keepalived is easy:

• get the source
• untar gz, do a ./configure;make;make install
• we're done. one thing to note: keepalived looks for the headers in /usr/src/linux. Remember to sym link your linux source tree. That bit me.