Merge pull request #365 from mongodb/description-change-events

Add description change events.

lib/mongo/event.rb

@@ -14,18 +14,31 @@
 
 require 'mongo/event/publisher'
 require 'mongo/event/subscriber'
+require 'mongo/event/host_added'
+require 'mongo/event/host_removed'
 
 module Mongo
 
   module Event
 
-    ARBITER_ADDED     = "arbiter_added".freeze
-    ARBITER_REMOVED   = "arbiter_removed".freeze
+    # When a server description has a new host added.
+    #
+    # @since 3.0.0
+    HOST_ADDED = "host_added".freeze
 
-    SECONDARY_ADDED   = "server_added".freeze
-    SECONDARY_REMOVED = "server_removed".freeze
+    # When a server description has a host removed.
+    #
+    # @since 3.0.0
+    HOST_REMOVED = "host_removed".freeze
 
-    SERVER_PROMOTED   = "server_promoted".freeze
-    SERVER_DEMOTED    = "server_demoted".freeze
+    # When a server is to be added to a cluster.
+    #
+    # @since 3.0.0
+    SERVER_ADDED = "server_added".freeze
+
+    # When a server is to be removed from a cluster.
+    #
+    # @since 3.0.0
+    SERVER_REMOVED = "server_removed".freeze
   end
 end

lib/mongo/event/host_added.rb

@@ -0,0 +1,44 @@
+# Copyright (C) 2009-2014 MongoDB, Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+module Mongo
+  module Event
+
+    # This handles host added events for server descriptions.
+    #
+    # @since 3.0.0
+    class HostAdded
+
+      # @return [ Mongo::Server ] server The event publisher.
+      attr_reader :server
+
+      # Initialize the new host added event handler.
+      #
+      # @example Create the new handler.
+      #   HostAdded.new(server)
+      #
+      # @param [ Mongo::Server ] server The server to publish from.
+      #
+      # @since 3.0.0
+      def initialize(server)
+        @server = server
+      end
+
+      def handle(address)
+        # @todo: Log the description change here.
+        server.publish(Event::SERVER_ADDED, address)
+      end
+    end
+  end
+end

lib/mongo/event/host_removed.rb

@@ -0,0 +1,44 @@
+# Copyright (C) 2009-2014 MongoDB, Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+module Mongo
+  module Event
+
+    # This handles host removed events for server descriptions.
+    #
+    # @since 3.0.0
+    class HostRemoved
+
+      # @return [ Mongo::Server ] server The event publisher.
+      attr_reader :server
+
+      # Initialize the new host removed event handler.
+      #
+      # @example Create the new handler.
+      #   HostRemoved.new(server)
+      #
+      # @param [ Mongo::Server ] server The server to publish from.
+      #
+      # @since 3.0.0
+      def initialize(server)
+        @server = server
+      end
+
+      def handle(address)
+        # @todo: Log the description change here.
+        server.publish(Event::SERVER_REMOVED, address)
+      end
+    end
+  end
+end

lib/mongo/server.rb

@@ -24,6 +24,7 @@ module Mongo
   # @since 3.0.0
   class Server
     include Event::Publisher
+    include Event::Subscriber
 
     # The default time for a server to refresh its status is 5 seconds.
     #
@@ -52,6 +53,7 @@ def initialize(address, options = {})
       @address = Address.new(address)
       @options = options
       @mutex = Mutex.new
+      initialize_description!
       @refresh = Refresh.new(self, refresh_interval)
       @refresh.run
     end
@@ -60,15 +62,22 @@ def operable?
       true
     end
 
+    # Refresh the configuration for this server. Is thread-safe since the
+    # periodic refresh is invoked from another thread in order not to continue
+    # blocking operations on the current thread.
+    #
+    # @example Refresh the server.
+    #   server.refresh!
+    #
+    # @note Is mutable in that the underlying server description can get
+    #   mutated on this call.
+    #
+    # @return [ Server::Description ] The updated server description.
+    #
+    # @since 3.0.0
     def refresh!
       mutex.synchronize do
-        # Update the server description here. For changes in the description to
-        # the previous we need to fire events.
-        #
-        # refreshed = Description.new(read(refresh_command))
-        #
-        # publish(Event::SERVER_ADDED, address)
-        # publish(Event::SERVER_REMOVED, address)
+        description.update!(dispatch([ refresh_command ]))
       end
     end
 
@@ -108,16 +117,23 @@ def refresh_interval
 
     private
 
+    def initialize_description!
+      # @description = Description.new(dispatch([ refresh_command ]))
+      # subscribe_to(description, Event::HOST_ADDED, Event::HostAdded.new(self))
+      # subscribe_to(description, Event::HOST_REMOVED, Event::HostRemoved.new(self))
+    end
+
     def pool
       @pool ||= Pool.get(self)
     end
 
+    # @todo: Need to sort out read preference here.
     def refresh_command
       Protocol::Query.new(
         Database::ADMIN,
         Database::COMMAND,
         STATUS,
-        :limit => -1, :read => cluster.client.read_preference
+        :limit => -1
       )
     end
 

lib/mongo/server/description.rb

@@ -20,6 +20,7 @@ class Server
     #
     # @since 3.0.0
     class Description
+      include Event::Publisher
 
       # Constant for reading arbiter info from config.
       #
@@ -207,6 +208,41 @@ def secondary?
       def set_name
         config[SET_NAME]
       end
+
+      # Update this description with a new description. Will fire the
+      # necessary events depending on what has changed from the old description
+      # to the new one.
+      #
+      # @example Update the description with the new config.
+      #   description.update!({ "ismaster" => false })
+      #
+      # @note This modifies the state of the description.
+      #
+      # @param [ Hash ] new_config The new configuration.
+      #
+      # @return [ Description ] The updated description.
+      #
+      # @since 3.0.0
+      def update!(new_config)
+        find_new_servers(new_config)
+        find_removed_servers(new_config)
+        @config = new_config
+        self
+      end
+
+      private
+
+      def find_new_servers(new_config)
+        new_config[HOSTS].each do |host|
+          publish(Event::HOST_ADDED, host) unless hosts.include?(host)
+        end
+      end
+
+      def find_removed_servers(new_config)
+        hosts.each do |host|
+          publish(Event::HOST_REMOVED, host) unless new_config[HOSTS].include?(host)
+        end
+      end
     end
   end
 end

spec/mongo/client_spec.rb

@@ -194,15 +194,12 @@
   describe '#inspect' do
 
     let(:client) do
-      described_class.new(
-        ['1.0.0.1:2', '1.0.0.1:1'],
-        :read => :primary
-      )
+      described_class.new(['127.0.0.1:27017'], :read => :primary)
     end
 
     it 'returns the cluster information' do
       expect(client.inspect).to eq(
-        "<Mongo::Client:0x#{client.object_id} cluster=1.0.0.1:2, 1.0.0.1:1>"
+        "<Mongo::Client:0x#{client.object_id} cluster=127.0.0.1:27017>"
       )
     end
   end

spec/mongo/event/host_added_spec.rb

@@ -0,0 +1,20 @@
+require 'spec_helper'
+
+describe Mongo::Event::HostAdded do
+
+  describe '#handle' do
+
+    let(:server) do
+      double('server')
+    end
+
+    let(:handler) do
+      described_class.new(server)
+    end
+
+    it 'publishes the event from the server' do
+      expect(server).to receive(:publish).with(Mongo::Event::SERVER_ADDED, 'test')
+      handler.handle('test')
+    end
+  end
+end

spec/mongo/event/host_removed_spec.rb

@@ -0,0 +1,20 @@
+require 'spec_helper'
+
+describe Mongo::Event::HostRemoved do
+
+  describe '#handle' do
+
+    let(:server) do
+      double('server')
+    end
+
+    let(:handler) do
+      described_class.new(server)
+    end
+
+    it 'publishes the event from the server' do
+      expect(server).to receive(:publish).with(Mongo::Event::SERVER_REMOVED, 'test')
+      handler.handle('test')
+    end
+  end
+end