My application_helper had a basic gravatar function, but gravatar.com is best used cached.

   1  
   2  def gravatar(email, user='')
   3    "<img alt=\"#{user}'s image\" src=\"/gravatars/#{MD5.new(email)}.gif\" height=\"80\" width=\"80\"/>"
   4  end

lib/gravatar_api.rb:

   1  
   2  require 'rc_rest'
   3  class GravatarAPI < RCRest
   4  
   5    @@cache_dir = "/rails/gravatars/"
   6    cattr_accessor :cache_dir
   7  
   8    # from: http://www.gravatar.com/implement.php?#section_1_1
   9    # An optional "rating" parameter may follow with a value of [ G | PG | R | X ]
  10    # that determines the highest rating (inclusive) that will be returned.
  11    # see also rating guidelines: http://www.gravatar.com/rating.php
  12    @@acceptable_rating = "PG"
  13    cattr_accessor :acceptable_rating
  14  
  15    def wget_gravatar(md5)
  16      info = get_info md5
  17      # return true if file_expired && I decide on adding a time expiry :)
  18      `rm #{cache_dir}#{md5}.gif` if File.exists?("#{cache_dir}#{md5}.gif") || File.symlink?("#{cache_dir}#{md5}.gif")
  19      if info.success && GravatarAPI.rating_ok(acceptable_rating)
  20        `wget -r -O #{cache_dir}#{md5}.gif http://www.gravatar.com/avatar.php?gravatar_id=#{md5}`
  21        return true
  22      else
  23        `ln -s #{cache_dir}no_image.gif #{cache_dir}#{md5}.gif`
  24        return false
  25      end
  26    end
  27  
  28    def self.rating_ok(actual_rating)
  29      ratings = %w{ X R PG G }
  30      ratings.index(actual_rating) >= ratings.index(@@acceptable_rating)
  31    end
  32  
  33    class Error < RCRest::Error; end
  34  
  35    def initialize
  36    end
  37  
  38    def check_error(xml)
  39      raise Error, "unkown error" if !xml.elements['gravatar']
  40    end
  41  
  42    def make_url(md5)
  43      URI.parse "http://www.gravatar.com/info/md5/#{md5}"
  44    end
  45  
  46    Info = Struct.new :success, :rating, :xml
  47    def parse_response(xml)
  48      result = Info.new
  49  
  50      result.xml = xml
  51      result.success = xml.elements['gravatar/code'].text == "200"
  52  
  53      if result.success
  54        result.rating = xml.elements['gravatar/rating'].text
  55      end
  56  
  57      result
  58    end
  59  
  60    def get_info(md5)
  61      get md5
  62    end
  63  end

lib/tasks/gravatar.rake
The intention is for "sudo rake cache_gravatars" to be a cron job

   1  
   2  desc "wget's the gravatars for all the user emails in your database. call with RAILS_ENV=production or it defaults to development"
   3  task :cache_gravatars => :environment do |t|
   4    require 'md5'
   5    require 'gravatar_api'
   6    ActiveRecord::Base.establish_connection(RAILS_ENV.to_sym)
   7    g_api = GravatarAPI.new
   8    users = (User.find :all).collect {|u| u if u.email? }.compact
   9    users.each do |user|
  10      md5 = MD5.new(user.email).hexdigest
  11      has_g = g_api.wget_gravatar(md5)
  12      puts "added " + (has_g ? "file" : "symlink" ) + " for " + md5
  13      if has_g != user.has_gravatar? # Only update object if necessary
  14        user.has_gravatar = !user.has_gravatar
  15        user.update
  16      end
  17      #sleep(1) # you know, to play nice with gravatar.com if you have a gazillion records
  18    end
  19  end

Finally, the signup code does an extra call:

   1  
   2  def signup
   3    @user = User.new(params[:user])
   4    return unless request.post?
   5    begin
   6      g_api = GravatarAPI.new
   7      @user.has_gravatar = g_api.wget_gravatar( MD5.new(@user.email).hexdigest )
   8    rescue Exception => e
   9      logger.warn("unable to get gravatar info for user: " + @user.id)
  10      @user.has_gravatar = false
  11    end
  12    @user.save!
  13  ...

Migration used:

   1  
   2  class Gravatar < ActiveRecord::Migration
   3    def self.up
   4      add_column :users, :has_gravatar, :boolean, :default => false
   5    end
   6  
   7    def self.down
   8      remove_column :users, :has_gravatar
   9    end
  10  end

The deployment procedures adds a symbolic link from public/gravatars to /rails/gravatars.