Initial commit of master and slaves read/write split

lib/mongoid.rb

@@ -41,6 +41,7 @@
 require "mongoid/associations/options"
 require "mongoid/attributes"
 require "mongoid/callbacks"
+require "mongoid/collection"
 require "mongoid/commands"
 require "mongoid/config"
 require "mongoid/contexts"

lib/mongoid/collection.rb

@@ -0,0 +1,21 @@
+# encoding: utf-8
+require "mongoid/collections/cyclic_iterator"
+require "mongoid/collections/reader"
+require "mongoid/collections/writer"
+
+module Mongoid #:nodoc
+  class Collection
+
+    # Initialize a new Mongoid::Collection, setting up the master, slave, and
+    # name attributes. Masters will be used for writes, slaves for reads.
+    #
+    # Example:
+    #
+    # <tt>Mongoid::Collection.new(masters, slaves, "test")</tt>
+    def initialize(name)
+      # Get all the master db -> Mongoid.master
+      # Get all the slave dbs -> Mongoid.slaves
+      @name = name
+    end
+  end
+end

lib/mongoid/collections/cyclic_iterator.rb

@@ -0,0 +1,34 @@
+# encoding: utf-8
+module Mongoid #:nodoc:
+  module Collections #:nodoc:
+    class CyclicIterator
+
+      attr_reader :counter
+
+      # Performs iteration over an array, if the array gets to the end then loop
+      # back to the first.
+      #
+      # Example:
+      #
+      # <tt>CyclicIterator.new([ first, second ])</tt>
+      def initialize(array)
+        @array, @counter = array, -1
+      end
+
+      # Get the next element in the array. If the element is the last in the
+      # array then return the first.
+      #
+      # Example:
+      #
+      # <tt>iterator.next</tt>
+      #
+      # Returns:
+      #
+      # The next element in the array.
+      def next
+        (@counter == @array.size - 1) ? @counter = 0 : @counter = @counter + 1
+        @array[@counter]
+      end
+    end
+  end
+end

lib/mongoid/collections/reader.rb

@@ -0,0 +1,38 @@
+# encoding: utf-8
+module Mongoid #:nodoc:
+  module Collections #:nodoc:
+    class Reader
+
+      attr_reader :iterator
+
+      delegate \
+        :count,
+        :distinct,
+        :find,
+        :find_one,
+        :group,
+        :index_information,
+        :map_reduce,
+        :mapreduce,
+        :options,
+        :size, :to => :collection
+
+      # Create the new database reader. Will create a collection from the
+      # slave databases and cycle through them on each read.
+      #
+      # Example:
+      #
+      # <tt>Reader.new(slaves, "mongoid_people")</tt>
+      def initialize(slaves, name)
+        @iterator = CyclicIterator.new(
+          slaves.collect { |db| db.collection(name) }
+        )
+      end
+
+      protected
+      def collection
+        @iterator.next
+      end
+    end
+  end
+end

lib/mongoid/collections/writer.rb

@@ -0,0 +1,30 @@
+# encoding: utf-8
+module Mongoid #:nodoc:
+  module Collections #:nodoc:
+    class Writer
+      attr_reader :collection
+
+      delegate \
+        :<<,
+        :create_index,
+        :drop,
+        :drop_index,
+        :drop_indexes,
+        :insert,
+        :remove,
+        :rename,
+        :save,
+        :update, :to => :collection
+
+      # Create the new database writer. Will create a collection from the
+      # master database.
+      #
+      # Example:
+      #
+      # <tt>Writer.new(master, "mongoid_people")</tt>
+      def initialize(master_db, name)
+        @collection = master_db.collection(name)
+      end
+    end
+  end
+end

lib/mongoid/config.rb

@@ -6,15 +6,13 @@ class Config #:nodoc
     attr_accessor \
       :allow_dynamic_fields,
       :persist_in_safe_mode,
-      :raise_not_found_error,
-      :temp_collection_size
+      :raise_not_found_error
 
     # Defaults the configuration options to true.
     def initialize
       @allow_dynamic_fields = true
       @persist_in_safe_mode = true
       @raise_not_found_error = true
-      @temp_collection_size = 1048576
     end
 
     # Sets the Mongo::DB to be used.

lib/mongoid/criteria.rb

@@ -222,7 +222,18 @@ def self.translate(*args)
     end
 
     protected
-    # Determines the context to be used for this criteria.
+    # Determines the context to be used for this criteria. If the class is an
+    # embedded document, then thw context will be the array in the has_many
+    # association it is in. If the class is a root, then the database itself
+    # will be the context.
+    #
+    # Example:
+    #
+    # <tt>criteria#determine_context</tt>
+    #
+    # Returns:
+    #
+    # A enumerable or mongo context.
     def determine_context
       if @klass.embedded
         return Contexts::Enumerable.new(@selector, @options, @documents)
@@ -233,6 +244,12 @@ def determine_context
     # Filters the unused options out of the options +Hash+. Currently this
     # takes into account the "page" and "per_page" options that would be passed
     # in if using will_paginate.
+    #
+    # Example:
+    #
+    # Given a criteria with a selector of { :page => 1, :per_page => 40 }
+    #
+    # <tt>criteria.filter_options</tt> # selector: { :skip => 0, :limit => 40 }
     def filter_options
       page_num = @options.delete(:page)
       per_page_num = @options.delete(:per_page)
@@ -242,19 +259,33 @@ def filter_options
       end
     end
 
-    # Return the entries of the other criteria or the object.
+    # Return the entries of the other criteria or the object. Used for
+    # comparing criteria or an enumerable.
     def comparable(other)
       other.is_a?(Criteria) ? other.entries : other
     end
 
     # Update the selector setting the operator on the value for each key in the
     # supplied attributes +Hash+.
+    #
+    # Example:
+    #
+    # <tt>criteria.update_selector({ :field => "value" }, "$in")</tt>
     def update_selector(attributes, operator)
       attributes.each { |key, value| @selector[key] = { operator => value } }; self
     end
 
     class << self
-      # Return a criteria or single document based on an id search.
+      # Create a criteria or single document based on an id search. Will handle
+      # if a single id has been passed or mulitple ids.
+      #
+      # Example:
+      #
+      #   Criteria.id_criteria(Person, [1, 2, 3])
+      #
+      # Returns:
+      #
+      # The single or multiple documents.
       def id_criteria(klass, params)
         criteria = new(klass).id(params)
         result = params.is_a?(String) ? criteria.one : criteria.entries

lib/mongoid/criterion/union.rb

@@ -18,6 +18,9 @@ def identifiers
       # Perform a union of 2 criteria and return the new criteria. The first
       # pass executes both sides and merges the collections together.
       #
+      # Note this operation can we extremely memory instensive for large
+      # collections - use with caution.
+      #
       # Example:
       #
       # <tt>criteria.or(other_criteria)</tt>

spec/spec_helper.rb

@@ -13,7 +13,16 @@
 require "spec"
 
 Mongoid.configure do |config|
-  config.database = Mongo::Connection.new.db("mongoid_test")
+  name = "mongoid_test"
+  config.database = Mongo::Connection.new.db(name)
+  # config.masters = [
+    # Mongo::Connection.new(host, port).db(name),
+    # Mongo::Connection.new(host, port).db(name)
+  # ]
+  # config.slaves = [
+    # Mongo::Connection.new(host, port, :slave_ok => true).db(name),
+    # Mongo::Connection.new(host, port, :slave_ok => true).db(name)
+  # ]
 end
 
 Dir[File.join(MODELS, "*.rb")].sort.each {|file| require File.basename(file) }

spec/unit/mongoid/collection_spec.rb

@@ -0,0 +1,34 @@
+require "spec_helper"
+
+describe Mongoid::Collection do
+
+  let(:master) do
+    stub.quacks_like(Mongo::DB.allocate)
+  end
+
+  let(:slave_one) do
+    stub.quacks_like(Mongo::DB.allocate)
+  end
+
+  let(:slave_two) do
+    stub.quacks_like(Mongo::DB.allocate)
+  end
+
+  let(:slaves) do
+    [ slave_one, slave_two ]
+  end
+
+  describe "#initialize" do
+
+    let(:collection) do
+      Mongoid::Collection.new(master, slaves, "mongoid_test")
+    end
+
+    it "sets the master db"
+
+    it "sets the slave dbs"
+
+    it "sets the name"
+  end
+
+end

spec/unit/mongoid/collections/cyclic_iterator_spec.rb

@@ -0,0 +1,75 @@
+require "spec_helper"
+
+describe Mongoid::Collections::CyclicIterator do
+
+  before do
+    @first = stub
+    @second = stub
+    @third = stub
+    @fourth = stub
+  end
+
+  let(:array) do
+    [ @first, @second, @third, @fourth ]
+  end
+
+  describe "#initialize" do
+
+    let(:iterator) do
+      Mongoid::Collections::CyclicIterator.new(array)
+    end
+
+    it "defaults the counter to -1" do
+      iterator.counter.should == -1
+    end
+  end
+
+  describe "#next" do
+
+    context "when the iterator has just been created" do
+
+      let(:iterator) do
+        Mongoid::Collections::CyclicIterator.new(array)
+      end
+
+      it "returns the first element" do
+        iterator.next.should == @first
+      end
+    end
+
+    context "when the iterator is in the middle" do
+
+      let(:iterator) do
+        Mongoid::Collections::CyclicIterator.new(array)
+      end
+
+      before do
+        2.times { iterator.next }
+      end
+
+      it "returns the next element given the index" do
+        iterator.next.should == @third
+      end
+    end
+
+    context "when the iterator is on the last element" do
+
+      let(:iterator) do
+        Mongoid::Collections::CyclicIterator.new(array)
+      end
+
+      before do
+        4.times { iterator.next }
+      end
+
+      it "returns the first element" do
+        iterator.next.should == @first
+      end
+
+      it "resets the counter" do
+        iterator.next
+        iterator.counter.should == 0
+      end
+    end
+  end
+end