Effectif Development

The images, CSS and JavaScript files served up by your Rails application can usually be cached by the web browser, rather than being downloaded (or checked) every time the browser loads a page on your site. For a properly configured site the net effect is faster page load times and a vastly improved user experience. Rails gives you some help here, but it doesn’t happen automatically – you need to configure your web server to set the HTTP Expires header. This article explains how to configure the expires header for a Rails application running behind the nginx HTTP proxy server.

I was testing a freshly deployed web site for a client the other day before they’d setup their DNS entry, and added the server to my Mac’s /etc/hosts file. It looked something like this:

208.75.85.73    www.clientsite.com

When I’d finished my testing I removed the entry from /etc/hosts. On most Unix systems that’s enough to eradicate all traces of your meddling, but not on the Mac. Any IP address that you add to /etc/hosts gets cached by the operating system.

After a bit of poking around I discovered lookupd. On Tiger you can flush the cache by entering this in the terminal:

lookupd -flushcache

On Leopard the lookupd command appears to have been replaced with dscacheutil. I’ve not had to clear my cache on Leopard yet, so whether it works in quite the same way remains to be seen.

Update: The HostsWidget Dashboard widget appears to solve the same problem rather well.

God is a very neat piece of software, frequently used by Rails developers to monitor mongrel servers, and restart them if/when they crash or use up too many system resources.

Its use isn't limited purely to monitoring web servers though; you can monitor pretty much anything you like. Read on to see how to configure it to monitor the Ruby job processing daemon, BackgrounDRb.

I used to work for a company that was in the business of deploying laptops running Linux into hospitals. We automated the installation of these laptops to such a degree that all we had to do build a new laptop was unwrap it, plug it into an ethernet network and turn it on. We used PXE boot and our own bespoke deployment system to achieve it. It even supported deploying automatic configuration updates over a mobile phone connection, while the laptops were in a different country.

It never seems to be worth going to the effort to setup a tool like puppet when configuring a new desktop computer, a virtual server to run your blog, or a VPS for a small client who is keen to keep the budget down. But why should automation be expensive?

If you like the idea of an automated server build on the cheap, read on...