Yesterday I started playing with basic caching for PriceChirp and tried what I thought would be easy. Boy was I wrong. It turns out what I was attempting to do is not supported by :memory_store in the development environment. Before moving to :mem_cache_store, I was able to find a work around. The work around is outlined below for those who do not have the option of using memcached. However, if you can use memcached, it is by far the better route to take.

My goal was to cut down on the number of database hit by caching the resultant ActiveRecord object in :memory_store.

I created a module I am also using both in rails and for some batch processing outside of rails. In order to ensure my data was formatted the same with both environments, I needed to figure out how to get access to the active_view helper number_to_currency outside of rails. Here is how I did it:

require 'rubygems'
require 'action_view'
 
def number_to_currency(number, options = {})
  ActionView::Base.new.number_to_currency(number, options)
end

Found an issue with open-uri because today Amazon's API is wonky. The same issue will occur when accessing any remote data via open-uri (like a RSS feed) if the data source is going to slow. The relevant part of my ruby code looks like:

  begin
    doc = Nokogiri(open(api_url))
  rescue
    print "Connection failed: #{$!}\n"
    next
  end

For some reason, the rescue does not catch a timeout error.

/usr/lib64/ruby/1.8/timeout.rb:54:in `rbuf_fill': execution expired (Timeout::Error)

Explicitly catching the timeout error fixes the code.

  begin
    doc = Nokogiri(open(api_url))
  rescue Timeout::Error
    print "Timeout::Error: #{$!}\n"
    next
  rescue
    print "Connection failed: #{$!}\n"
    next
  end

Good to know, as you never know when your remote data provider will be slow.

Code updated 9/18/2009

This week I added sitemap files to my rails site PriceChirp. Sitemaps are used to help search engines to find all your content. They are especially helpful in enumerating pages that are difficult for web crawlers to discover, such as content from database searches.

The web is full of instructions on how to generate sitemaps on the fly using rxml templates. This does not scale well if your site has thousands of links. A better method is to periodically generate site maps and serve these cached files when requested.

www.fortytwo.gr has a good example for generating sitemaps with rails. I've taken his code and fixed/extended it to fit my needs.

Understanding Sitemaps

Google's sitemap howto.

Basically, there are two types of sitemap files: