Added cache for application settings (Setting model).

Once the values are cached, only one database query is done at each user request (to check if the cache is still valid).

git-svn-id: http://redmine.rubyforge.org/svn/trunk@685 e93f8b46-1217-0410-a6f0-8f06a7374b81

app/controllers/application.rb

@@ -32,6 +32,7 @@ class ApplicationController < ActionController::Base
   end
   
   def user_setup
+    Setting.check_cache
     if session[:user_id]
       # existing session
       User.current = User.find(session[:user_id])

app/models/setting.rb

@@ -23,25 +23,28 @@ class Setting < ActiveRecord::Base
   validates_uniqueness_of :name
   validates_inclusion_of :name, :in => @@available_settings.keys
   validates_numericality_of :value, :only_integer => true, :if => Proc.new { |setting| @@available_settings[setting.name]['format'] == 'int' }  
-  
-  def self.get(name)
-    name = name.to_s
-    setting = find_by_name(name)
-    setting ||= new(:name => name, :value => @@available_settings[name]['default']) if @@available_settings.has_key? name
-    setting
-  end
-  
+
+  # Hash used to cache setting values
+  @cached_settings = {}
+  @cached_cleared_on = Time.now
+    
+  # Returns the value of the setting named name
   def self.[](name)
-    get(name).value
+    value = @cached_settings[name]
+    value ? value : (@cached_settings[name] = find_or_default(name).value)
   end
   
   def self.[]=(name, value)
-    setting = get(name)
+    setting = find_or_default(name)
     setting.value = (value ? value.to_s : "")
+    @cached_settings[name] = nil
     setting.save
     setting.value
   end
   
+  # Defines getter and setter for each setting
+  # Then setting values can be read using: Setting.some_setting_name
+  # or set using Setting.some_setting_name = "some value"
   @@available_settings.each do |name, params|
     src = <<-END_SRC
     def self.#{name}
@@ -58,4 +61,26 @@ class Setting < ActiveRecord::Base
     END_SRC
     class_eval src, __FILE__, __LINE__
   end
+  
+  # Checks if settings have changed since the values were read
+  # and clears the cache hash if it's the case
+  # Called once per request
+  def self.check_cache
+    settings_updated_on = Setting.maximum(:updated_on)
+    if settings_updated_on && @cached_cleared_on <= settings_updated_on
+      @cached_settings.clear
+      @cached_cleared_on = Time.now
+      logger.info "Settings cache cleared." if logger
+    end
+  end
+  
+private
+  # Returns the Setting instance for the setting named name
+  # (record found in database or new record with default value)
+  def self.find_or_default(name)
+    name = name.to_s
+    raise "There's no setting named #{name}" unless @@available_settings.has_key?(name)    
+    setting = find_by_name(name)
+    setting ||= new(:name => name, :value => @@available_settings[name]['default']) if @@available_settings.has_key? name
+  end
 end

db/migrate/065_add_settings_updated_on.rb

@@ -0,0 +1,11 @@
+class AddSettingsUpdatedOn < ActiveRecord::Migration
+  def self.up
+    add_column :settings, :updated_on, :timestamp
+    # set updated_on
+    Setting.find(:all).each(&:save)
+  end
+
+  def self.down
+    remove_column :settings, :updated_on
+  end
+end