[JAVA-275]: with default write concern (no getLastError), if master changes in repl set, writes will fail undetected forever

Author: agirbal

src/main/com/mongodb/Mongo.java

@@ -482,7 +482,11 @@ void _applyMongoOptions() {
         if (_options.slaveOk) slaveOk();
         setWriteConcern( _options.getWriteConcern() );
     }
-    
+
+    DBTCPConnector getConnector() {
+        return _connector;
+    }
+
     final ServerAddress _addr;
     final List<ServerAddress> _addrs;
     final MongoOptions _options;

src/main/com/mongodb/ReplicaSetStatus.java

@@ -304,6 +304,10 @@ synchronized void updateAll(){
                     it.remove();
             }
         }
+
+        // force check on master
+        // otherwise master change may go unnoticed for a while if no write concern
+        _mongo.getConnector().checkMaster(true, false);
     }
 
     List<ServerAddress> getServerAddressList() {