Migrate Handler to new plugin style

Note: This is not stable API yet.

Before:

    # lib/droonga/plugin/handler/my_handler.rb

    require "droonga/handler_plugin"

    module Droonga
      class MyHandler < Droonga::HandlerPlugin
        repository.register("my-handler", self)

        command :my_command
        def my_command(message, messenger)
        end
      end
    end

After:

    # lib/droonga/plugins/my_plugin.rb

    require "droonga/plugin"

    module Droonga
      module Plugins
        module MyPlugin
          Plugin.registry.register("my-plugin", self)

          class Handler < Droonga::Handler
            message.type = "my-command"

            def handle(message, messenger)
            end
          end
        end
      end
    end

lib/droonga/catalog/base.rb

@@ -54,8 +54,7 @@ def get_partitions(name)
         results = {}
         @data["datasets"].each do |key, dataset|
           workers = dataset["workers"]
-          handler = dataset["handler"] || {}
-          plugins = handler["plugins"] || dataset["plugins"]
+          plugins = dataset["plugins"]
           dataset["ring"].each do |key, part|
             part["partitions"].each do |range, partitions|
               partitions.each do |partition|
@@ -65,7 +64,7 @@ def get_partitions(name)
                   options = {
                     :database => path,
                     :n_workers => workers,
-                    :handlers => plugins
+                    :plugins => plugins
                   }
                   results[partition] = options
                 end

lib/droonga/plugin/handler/search.rb → lib/droonga/handler.rb

@@ -1,6 +1,4 @@
-# -*- coding: utf-8 -*-
-#
-# Copyright (C) 2013 Droonga Project
+# Copyright (C) 2014 Droonga Project
 #
 # This library is free software; you can redistribute it and/or
 # modify it under the terms of the GNU Lesser General Public
@@ -15,23 +13,30 @@
 # License along with this library; if not, write to the Free Software
 # Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 
-require "droonga/handler_plugin"
-require "droonga/searcher"
+require "droonga/pluggable"
+require "droonga/plugin/metadata/input_message"
+require "droonga/plugin/metadata/handler_action"
 
 module Droonga
-  class SearchHandler < Droonga::HandlerPlugin
-    repository.register("search", self)
+  class Handler
+    extend Pluggable
+
+    class << self
+      def message
+        Plugin::Metadata::InputMessage.new(self)
+      end
 
-    command :search
-    def search(message, messenger)
-      searcher = Droonga::Searcher.new(@context)
-      values = {}
-      request = message.request
-      raise Droonga::Searcher::NoQuery.new unless request
-      searcher.search(request["queries"]).each do |output, value|
-        values[output] = value
+      def action
+        Plugin::Metadata::HandlerAction.new(self)
       end
-      messenger.emit(values)
+    end
+
+    def initialize(name, context)
+      @name = name
+      @context = context
+    end
+
+    def handle(message, messenger)
     end
   end
 end

lib/droonga/handler_runner.rb

@@ -18,15 +18,10 @@
 require "droonga/forwarder"
 require "droonga/handler_message"
 require "droonga/handler_messenger"
-require "droonga/legacy_pluggable"
-require "droonga/handler_plugin"
+require "droonga/handler"
 
 module Droonga
   class HandlerRunner
-    include LegacyPluggable
-
-    attr_reader :context, :name
-
     def initialize(loop, options={})
       @loop = loop
       @options = options
@@ -43,7 +38,6 @@ def start
 
     def shutdown
       $log.trace("#{log_tag}: shutdown: start")
-      super
       @forwarder.shutdown
       if @database
         @database.close
@@ -54,20 +48,24 @@ def shutdown
     end
 
     def prefer_synchronous?(command)
-      find_plugin(command).prefer_synchronous?(command)
+      find_handler_class(command).action.synchronous?
+    end
+
+    def processable?(command)
+      not find_handler_class(command).nil?
     end
 
     def process(message)
       $log.trace("#{log_tag}: process: start")
       command = message["type"]
-      plugin = find_plugin(command)
-      if plugin.nil?
-        $log.trace("#{log_tag}: process: done: no plugin: <#{command}>")
+      handler_class = find_handler_class(command)
+      if handler_class.nil?
+        $log.trace("#{log_tag}: process: done: no handler: <#{command}>")
         return
       end
-      process_command(plugin, command, message)
+      process_command(handler_class, command, message)
       $log.trace("#{log_tag}: process: done: <#{command}>",
-                 :plugin => plugin.class)
+                 :handler => handler_class)
     end
 
     private
@@ -76,20 +74,27 @@ def prepare
         @context = Groonga::Context.new
         @database = @context.open_database(@database_name)
       end
-      load_plugins(@options[:handlers] || [])
+      @handler_classes = Handler.find_sub_classes(@options[:plugins] || [])
       @forwarder = Forwarder.new(@loop)
     end
 
-    def instantiate_plugin(name)
-      HandlerPlugin.repository.instantiate(name, self)
+    def find_handler_class(command)
+      @handler_classes.find do |handler_class|
+        handler_class.message.type == command
+      end
     end
 
-    def process_command(plugin, command, raw_message)
+    def process_command(handler_class, command, raw_message)
       handler_message = HandlerMessage.new(raw_message)
       handler_message.validate
 
       messenger = HandlerMessenger.new(@forwarder, handler_message, @options)
-      plugin.process(command, handler_message, messenger)
+      handler = handler_class.new(@name, @context)
+      begin
+        handler.handle(handler_message, messenger)
+      rescue MessageProcessingError => error
+        messenger.error(error.status_code, error.response_body)
+      end
     end
 
     def log_tag

lib/droonga/plugin.rb

@@ -15,6 +15,7 @@
 
 require "droonga/plugin_registry"
 require "droonga/adapter"
+require "droonga/handler"
 
 module Droonga
   module Plugin