From 02cd38fce0d0e80854860bc19a7158930389b03b Mon Sep 17 00:00:00 2001
From: Jim Menard <jim@10gen.com>
Date: Tue, 16 Dec 2008 17:35:31 -0500
Subject: [PATCH] Added XGen::Mongo::Driver::DB.master?

---
 README.rdoc          |  7 ++-----
 lib/mongo/db.rb      | 27 ++++++++++++++++++---------
 tests/test_db_api.rb |  4 ++++
 3 files changed, 24 insertions(+), 14 deletions(-)

diff --git a/README.rdoc b/README.rdoc
index 16fbfad..64b6c70 100644
--- a/README.rdoc
+++ b/README.rdoc
@@ -54,11 +54,8 @@ type
 
 = To Do
 
-* Add way to ask db if it is master or slave. Mongo needs to add this, first.
-
-* Once Mongo can tell us if an instance is master or slave, add a way to
-  specify a collection of databases on startup (a simple array of IP
-  address/port numbers, perhaps, or a hash or something). The driver would
+* Add a way to specify a collection of databases on startup (a simple array of
+  IP address/port numbers, perhaps, or a hash or something). The driver would
   then find the master and, on each subsequent command, ask that machine if it
   is the master before proceeding.
 
diff --git a/lib/mongo/db.rb b/lib/mongo/db.rb
index 0971b34..5b8a637 100644
--- a/lib/mongo/db.rb
+++ b/lib/mongo/db.rb
@@ -72,8 +72,8 @@ module XGen
           oh = OrderedHash.new
           oh[:create] = name
           doc = db_command(oh.merge(options))
-          o = doc['ok']
-          return Collection.new(self, name) if o.kind_of?(Numeric) && (o.to_i == 1 || o.to_i == 0)
+          ok = doc['ok']
+          return Collection.new(self, name) if ok.kind_of?(Numeric) && (ok.to_i == 1 || ok.to_i == 0)
           raise "Error creating collection: #{doc.inspect}"
         end
 
@@ -100,9 +100,15 @@ module XGen
           return true if coll == nil
           coll.drop_indexes     # Mongo requires that we drop indexes manually
 
-          doc = db_command(:drop => name)
-          o = doc['ok']
-          return o.kind_of?(Numeric) && o.to_i == 1
+          ok?(db_command(:drop => name))
+        end
+
+        # Returns true if this database is a master (or is not paired with any
+        # other database), false if it is a slave.
+        def master?
+          doc = db_command(:ismaster => 1)
+          is_master = doc['ismaster']
+          ok?(doc) && is_master.kind_of?(Numeric) && is_master.to_i == 1
         end
 
         def close
@@ -142,8 +148,7 @@ module XGen
           oh[:count] = collection_name
           oh[:query] = selector
           doc = db_command(oh)
-          o = doc['ok']
-          return doc['n'].to_i if o.to_i == 1
+          return doc['n'].to_i if ok?(doc)
           raise "Error with count command: #{doc.inspect}"
         end
 
@@ -152,8 +157,7 @@ module XGen
           oh[:deleteIndexes] = collection_name
           oh[:index] = name
           doc = db_command(oh)
-          o = doc['ok']
-          raise "Error with drop_index command: #{doc.inspect}" unless o.kind_of?(Numeric) && o.to_i == 1
+          raise "Error with drop_index command: #{doc.inspect}" unless ok?(doc)
         end
 
         def index_information(collection_name)
@@ -199,6 +203,11 @@ module XGen
 
         protected
 
+        def ok?(doc)
+          ok = doc['ok']
+          ok.kind_of?(Numeric) && ok.to_i == 1
+        end
+
         # DB commands need to be ordered, so selector must be an OrderedHash
         # (or a Hash with only one element). What DB commands really need is
         # that the "command" key be first.
diff --git a/tests/test_db_api.rb b/tests/test_db_api.rb
index 6a0da23..93f423b 100644
--- a/tests/test_db_api.rb
+++ b/tests/test_db_api.rb
@@ -246,4 +246,8 @@ class DBAPITest < Test::Unit::TestCase
     end
   end
 
+  def test_ismaster
+    assert @db.master?
+  end
+
 end