Added multi process support (share updated settings over multiple processes).

app/models/setting.rb

@@ -7,15 +7,75 @@ class Setting < ApplicationModel
   store         :preferences
   before_create :state_check, :set_initial
   before_update :state_check
-  after_create  :delete_cache
-  after_update  :delete_cache
+  after_create  :reset_cache
+  after_update  :reset_cache
+  after_destroy :reset_cache
 
   @@current        = {} # rubocop:disable Style/ClassVars
+  @@change_id      = nil # rubocop:disable Style/ClassVars
+  @@lookup_at      = nil # rubocop:disable Style/ClassVars
+  @@lookup_timeout = 2.minutes # rubocop:disable Style/ClassVars
 
+=begin
+
+set config setting
+
+  Setting.set('some_config_name', some_value)
+
+=end
+
+  def self.set(name, value)
+    setting = Setting.find_by( name: name )
+    if !setting
+      fail "Can't find config setting '#{name}'"
+    end
+    setting.state = { value: value }
+    setting.save
+    logger.info "Setting.set(#{name}, #{value.inspect})"
+  end
+
+=begin
+
+get config setting
+
+  value = Setting.get('some_config_name')
+
+=end
+
+  def self.get(name)
+    load
+    @@current[:settings_config][name]
+  end
+
+=begin
+
+reset config setting to default
+
+  Setting.reset('some_config_name')
+
+=end
+
+  def self.reset(name)
+    setting = Setting.find_by( name: name )
+    if !setting
+      fail "Can't find config setting '#{name}'"
+    end
+    setting.state = setting.state_initial
+    setting.save
+    logger.info "Setting.reset(#{name}, #{setting.state.inspect})"
+    load
+    @@current[:settings_config][name]
+  end
+
+  private
+
+  # load values and cache them
   def self.load
 
     # check if config is already generated
-    return @@current[:settings_config] if @@current[:settings_config]
+    if @@current[:settings_config]
+      return @@current[:settings_config] if cache_valid?
+    end
 
     # read all config settings
     config = {}
@@ -33,52 +93,56 @@ class Setting < ApplicationModel
     }
 
     # store for class requests
-    @@current[:settings_config] = config
+    cache(config)
     config
   end
 
-  def self.set(name, value)
-    setting = Setting.find_by( name: name )
-    if !setting
-      fail "Can't find config setting '#{name}'"
-    end
-    setting.state = { value: value }
-    setting.save
-    logger.info "Setting.set() name:#{name}, value:#{value.inspect}"
-  end
-
-  def self.get(name)
-    load
-    @@current[:settings_config][name]
-  end
-
-  def self.reset(name)
-    setting = Setting.find_by( name: name )
-    if !setting
-      fail "Can't find config setting '#{name}'"
-    end
-    setting.state = setting.state_initial
-    setting.save
-    logger.info "Setting.reset() name:#{name}, value:#{setting.state.inspect}"
-    load
-    @@current[:settings_config][name]
-  end
-
-  private
-
-  def delete_cache
-    @@current[:settings_config] = nil
-  end
-
+  # set initial value in state_initial
   def set_initial
     self.state_initial = state
   end
 
+  # set new cache
+  def self.cache(config)
+    @@change_id = Cache.get('Setting::ChangeId') # rubocop:disable Style/ClassVars
+    @@current[:settings_config] = config
+    logger.debug "Setting.cache: set cache, #{@@change_id}"
+    @@lookup_at = Time.zone.now # rubocop:disable Style/ClassVars
+  end
+
+  # reset cache
+  def reset_cache
+    @@change_id = rand(999_999_999).to_s # rubocop:disable Style/ClassVars
+    logger.debug "Setting.reset_cache: set new cache, #{@@change_id}"
+
+    Cache.write('Setting::ChangeId', @@change_id, { expires_in: 24.hours })
+    @@current[:settings_config] = nil
+  end
+
+  # check if cache is still valid
+  def self.cache_valid?
+    if @@lookup_at && @@lookup_at > Time.zone.now - @@lookup_timeout
+      logger.debug 'Setting.cache_valid?: cache_id has beed set within last 2 minutes'
+      return true
+    end
+    change_id = Cache.get('Setting::ChangeId')
+    if change_id == @@change_id
+      @@lookup_at = Time.zone.now # rubocop:disable Style/ClassVars
+      logger.debug "Setting.cache_valid?: cache still valid, #{@@change_id}/#{change_id}"
+      return true
+    end
+    logger.debug "Setting.cache_valid?: cache has changed, #{@@change_id}/#{change_id}"
+    false
+  end
+
+  # convert state ot hash to be able to store it as store
   def state_check
 
-    return if !(state || state == false)
+    return if !state
+    return if state == false
 
-    return if !( !state.respond_to?('has_key?') || !state.key?(:value) )
+    return if state.respond_to?('has_key?')
+    return if state.key?(:value)
 
     self.state = { value: state }
   end