RUBY-115 tailable cursors

lib/mongo.rb

@@ -19,6 +19,7 @@ module Mongo
     OP_DELETE       = 2006
     OP_KILL_CURSORS = 2007
 
+    OP_QUERY_TAILABLE          = 2
     OP_QUERY_SLAVE_OK          = 4
     OP_QUERY_NO_CURSOR_TIMEOUT = 16
 

lib/mongo/cursor.rb

@@ -47,6 +47,7 @@ module Mongo
       @timeout    = options[:timeout]  || false
       @explain    = options[:explain]
       @socket     = options[:socket]
+      @tailable   = options[:tailable] || false
       @batch_size = options[:batch_size] || Mongo::Constants::DEFAULT_BATCH_SIZE
 
       @full_collection_name = "#{@collection.db.name}.#{@collection.name}"
@@ -251,7 +252,8 @@ module Mongo
     def query_opts
       timeout  = @timeout ? 0 : Mongo::Constants::OP_QUERY_NO_CURSOR_TIMEOUT
       slave_ok = @connection.slave_ok? ? Mongo::Constants::OP_QUERY_SLAVE_OK : 0
-      slave_ok + timeout
+      tailable = @tailable ? Mongo::Constants::OP_QUERY_TAILABLE : 0
+      slave_ok + timeout + tailable
     end
 
     # Get the query options for this Cursor.

test/collection_test.rb

@@ -594,4 +594,42 @@ class TestCollection < Test::Unit::TestCase
       end
     end
   end
+
+  context "Capped collections" do
+    setup do
+      @@db.drop_collection('log')
+      @capped = @@db.create_collection('log', :capped => true, :size => 1024)
+
+      10.times { |n| @capped.insert({:n => n}) }
+    end
+
+    should "find using a standard cursor" do
+      cursor = @capped.find
+      10.times do
+        assert cursor.next_document
+      end
+      assert_nil cursor.next_document
+      @capped.insert({:n => 100})
+      assert_nil cursor.next_document
+    end
+
+    should "" do
+      col = @@db['regular-collection']
+      col.insert({:a => 1000})
+      tail = Cursor.new(col, :tailable => true, :order => [['$natural', 1]])
+      assert_raise OperationFailure do
+        tail.next_document
+      end
+    end
+
+    should "find using a tailable cursor" do
+      tail = Cursor.new(@capped, :tailable => true, :order => [['$natural', 1]])
+      10.times do
+        assert tail.next_document
+      end
+      assert_nil tail.next_document
+      @capped.insert({:n => 100})
+      assert tail.next_document
+    end
+  end
 end