text: /**
   * Module dependencies.
   * @ignore
   */
  var QueryCommand = require('./commands/query_command').QueryCommand,
    DbCommand = require('./commands/db_command').DbCommand,
    MongoReply = require('./responses/mongo_reply').MongoReply,
    Admin = require('./admin').Admin,
    Collection = require('./collection').Collection,
    Server = require('./connection/server').Server,
    ReplSet = require('./connection/repl_set').ReplSet,
    ReadPreference = require('./connection/read_preference').ReadPreference,
    Mongos = require('./connection/mongos').Mongos,
    Cursor = require('./cursor').Cursor,
    EventEmitter = require('events').EventEmitter,
    inherits = require('util').inherits,
    crypto = require('crypto'),
    timers = require('timers'),
    utils = require('./utils'),
    parse = require('./connection/url_parser').parse;
  
  // Set processor, setImmediate if 0.10 otherwise nextTick
  var processor = timers.setImmediate ? timers.setImmediate : process.nextTick;
  processor = process.nextTick
  
  /**
   * Create a new Db instance.
   *
   * Options
   *  - **w**, {Number/String, > -1 || 'majority' || tag name} the write concern for the operation where < 1 is no acknowlegement of write and w >= 1, w = 'majority' or tag acknowledges the write
   *  - **wtimeout**, {Number, 0} set the timeout for waiting for write concern to finish (combines with w option)
   *  - **fsync**, (Boolean, default:false) write waits for fsync before returning
   *  - **journal**, (Boolean, default:false) write waits for journal sync before returning
   *  - **readPreference** {String}, the prefered read preference (ReadPreference.PRIMARY, ReadPreference.PRIMARY_PREFERRED, ReadPreference.SECONDARY, ReadPreference.SECONDARY_PREFERRED, ReadPreference.NEAREST).
   *  - **native_parser** {Boolean, default:false}, use c++ bson parser.
   *  - **forceServerObjectId** {Boolean, default:false}, force server to create _id fields instead of client.
   *  - **pkFactory** {Object}, object overriding the basic ObjectID primary key generation.
   *  - **serializeFunctions** {Boolean, default:false}, serialize functions.
   *  - **raw** {Boolean, default:false}, peform operations using raw bson buffers.
   *  - **recordQueryStats** {Boolean, default:false}, record query statistics during execution.
   *  - **retryMiliSeconds** {Number, default:5000}, number of miliseconds between retries.
   *  - **numberOfRetries** {Number, default:5}, number of retries off connection.
   *  - **logger** {Object, default:null}, an object representing a logger that you want to use, needs to support functions debug, log, error **({error:function(message, object) {}, log:function(message, object) {}, debug:function(message, object) {}})**.
   * 
   * Deprecated Options 
   *  - **safe** {true | {w:n, wtimeout:n} | {fsync:true}, default:false}, executes with a getLastError command returning the results of the command on MongoDB.
   *
   * @class Represents a Db
   * @param {String} databaseName name of the database.
   * @param {Object} serverConfig server config object.
   * @param {Object} [options] additional options for the collection.
   */
  function Db(databaseName, serverConfig, options) {
    if(!(this instanceof Db)) return new Db(databaseName, serverConfig, options);
  
    EventEmitter.call(this);
    this.databaseName = databaseName;
    this.serverConfig = serverConfig;
    this.options = options == null ? {} : options;
    // State to check against if the user force closed db
    this._applicationClosed = false;
    // Fetch the override flag if any
    var overrideUsedFlag = this.options['override_used_flag'] == null ? false : this.options['override_used_flag'];
  
    // Verify that nobody is using this config
    if(!overrideUsedFlag && this.serverConfig != null && typeof this.serverConfig == 'object' && this.serverConfig._isUsed && this.serverConfig._isUsed()) {    
      throw new Error("A Server or ReplSet instance cannot be shared across multiple Db instances");
    } else if(!overrideUsedFlag && typeof this.serverConfig == 'object'){
      // Set being used
      this.serverConfig._used = true;
    }
  
    // Ensure we have a valid db name
    validateDatabaseName(databaseName);
  
    // Contains all the connections for the db
    try {
      this.native_parser = this.options.native_parser;
      // The bson lib
      var bsonLib = this.bsonLib = this.options.native_parser ? require('bson').BSONNative : require('bson').BSONPure;
      // Fetch the serializer object
      var BSON = bsonLib.BSON;
      // Create a new instance
      this.bson = new BSON([bsonLib.Long, bsonLib.ObjectID, bsonLib.Binary, bsonLib.Code, bsonLib.DBRef, bsonLib.Symbol, bsonLib.Double, bsonLib.Timestamp, bsonLib.MaxKey, bsonLib.MinKey]);
      // Backward compatibility to access types
      this.bson_deserializer = bsonLib;
      this.bson_serializer = bsonLib;
    } catch (err) {
      // If we tried to instantiate the native driver
      var msg = "Native bson parser not compiled, please compile "
              + "or avoid using native_parser=true";
      throw Error(msg);
    }
  
    // Internal state of the server
    this._state = 'disconnected';
  
    this.pkFactory = this.options.pk == null ? bsonLib.ObjectID : this.options.pk;
    this.forceServerObjectId = this.options.forceServerObjectId != null ? this.options.forceServerObjectId : false;
  
    // Added safe
    this.safe = this.options.safe == null ? false : this.options.safe;  
  
    // If we have not specified a "safe mode" we just print a warning to the console
    if(this.options.safe == null && this.options.w == null && this.options.journal == null && this.options.fsync == null) {
      console.log("========================================================================================");
      console.log("=  Please ensure that you set the default write concern for the database by setting    =");
      console.log("=   one of the options                                                                 =");
      console.log("=                                                                                      =");
      console.log("=     w: (value of > -1 or the string 'majority'), where < 1 means                     =");
      console.log("=        no write acknowlegement                                                       =");
      console.log("=     journal: true/false, wait for flush to journal before acknowlegement             =");
      console.log("=     fsync: true/false, wait for flush to file system before acknowlegement           =");
      console.log("=                                                                                      =");
      console.log("=  For backward compatibility safe is still supported and                              =");
      console.log("=   allows values of [true | false | {j:true} | {w:n, wtimeout:n} | {fsync:true}]      =");
      console.log("=   the default value is false which means the driver receives does not                =");
      console.log("=   return the information of the success/error of the insert/update/remove            =");
      console.log("=                                                                                      =");
      console.log("=   ex: new Db(new Server('localhost', 27017), {safe:false})                           =");
      console.log("=                                                                                      =");
      console.log("=   http://www.mongodb.org/display/DOCS/getLastError+Command                           =");
      console.log("=                                                                                      =");
      console.log("=  The default of no acknowlegement will change in the very near future                =");
      console.log("=                                                                                      =");
      console.log("=  This message will disappear when the default safe is set on the driver Db           =");
      console.log("========================================================================================");
    }
  
    // Internal states variables
    this.notReplied ={};
    this.isInitializing = true;
    this.auths = [];
    this.openCalled = false;
  
    // Command queue, keeps a list of incoming commands that need to be executed once the connection is up
    this.commands = [];
  
    // Set up logger
    this.logger = this.options.logger != null
      && (typeof this.options.logger.debug == 'function')
      && (typeof this.options.logger.error == 'function')
      && (typeof this.options.logger.log == 'function')
        ? this.options.logger : {error:function(message, object) {}, log:function(message, object) {}, debug:function(message, object) {}};
    // Allow slaveOk
    this.slaveOk = this.options["slave_ok"] == null ? false : this.options["slave_ok"];
  
    var self = this;
    // Associate the logger with the server config
    this.serverConfig.logger = this.logger;
    if(this.serverConfig.strategyInstance) this.serverConfig.strategyInstance.logger = this.logger;
    this.tag = new Date().getTime();
    // Just keeps list of events we allow
    this.eventHandlers = {error:[], parseError:[], poolReady:[], message:[], close:[]};
  
    // Controls serialization options
    this.serializeFunctions = this.options.serializeFunctions != null ? this.options.serializeFunctions : false;
  
    // Raw mode
    this.raw = this.options.raw != null ? this.options.raw : false;
  
    // Record query stats
    this.recordQueryStats = this.options.recordQueryStats != null ? this.options.recordQueryStats : false;
  
    // If we have server stats let's make sure the driver objects have it enabled
    if(this.recordQueryStats == true) {
      this.serverConfig.enableRecordQueryStats(true);
    }
  
    // Retry information
    this.retryMiliSeconds = this.options.retryMiliSeconds != null ? this.options.retryMiliSeconds : 1000;
    this.numberOfRetries = this.options.numberOfRetries != null ? this.options.numberOfRetries : 60;
  
    // Set default read preference if any
    this.readPreference = this.options.readPreference;
  };
  
  /**
   * @ignore
   */
  function validateDatabaseName(databaseName) {
    if(typeof databaseName !== 'string') throw new Error("database name must be a string");
    if(databaseName.length === 0) throw new Error("database name cannot be the empty string");
  
    var invalidChars = [" ", ".", "$", "/", "\\"];
    for(var i = 0; i < invalidChars.length; i++) {
      if(databaseName.indexOf(invalidChars[i]) != -1) throw new Error("database names cannot contain the character '" + invalidChars[i] + "'");
    }
  }
  
  /**
   * @ignore
   */
  inherits(Db, EventEmitter);
  
  /**
   * Initialize the database connection.
   *
   * @param {Function} callback this will be called after executing this method. The first parameter will contain the Error object if an error occured, or null otherwise. While the second parameter will contain the index information or null if an error occured.
   * @return {null}
   * @api public
   */
  Db.prototype.open = function(callback) {
    var self = this;
  
    // Check that the user has not called this twice
    if(this.openCalled) {
      // Close db
      this.close();
      // Throw error
      throw new Error("db object already connecting, open cannot be called multiple times");
    }
  
    // If we have a specified read preference
    if(this.readPreference != null) this.serverConfig.setReadPreference(this.readPreference);
  
    // Set that db has been opened
    this.openCalled = true;
  
    // Set the status of the server
    self._state = 'connecting';
    // Set up connections
    if(self.serverConfig instanceof Server || self.serverConfig instanceof ReplSet || self.serverConfig instanceof Mongos) {
      self.serverConfig.connect(self, {firstCall: true}, function(err, result) {
        if(err != null) {
          // Set that db has been closed
          self.openCalled = false;
          // Return error from connection
          return callback(err, null);
        }
        // Set the status of the server
        self._state = 'connected';
        // If we have queued up commands execute a command to trigger replays
        if(self.commands.length > 0) _execute_queued_command(self);
        // Callback
        return callback(null, self);
      });
    } else {
      return callback(Error("Server parameter must be of type Server, ReplSet or Mongos"), null);
    }
  };
  
  // Execute any baked up commands
  var _execute_queued_command = function(self) {
    // Execute any backed up commands
    processor(function() {
      // Execute any backed up commands
      while(self.commands.length > 0) {
        // Fetch the command
        var command = self.commands.shift();
        // Execute based on type
        if(command['type'] == 'query') {
          __executeQueryCommand(self, command['db_command'], command['options'], command['callback']);
        } else if(command['type'] == 'insert') {
          __executeInsertCommand(self, command['db_command'], command['options'], command['callback']);
        }
      }
    });  
  }
  
  /**
   * Create a new Db instance sharing the current socket connections.
   *
   * @param {String} dbName the name of the database we want to use.
   * @return {Db} a db instance using the new database.
   * @api public
   */
  Db.prototype.db = function(dbName) {
    // Copy the options and add out internal override of the not shared flag
    var options = {};
    for(var key in this.options) {
      options[key] = this.options[key];
    }
  
    // Add override flag
    options['override_used_flag'] = true;
    // Create a new db instance
    var newDbInstance = new Db(dbName, this.serverConfig, options);
    //copy over any auths, we may need them for reconnecting
    if (this.serverConfig.db) {
      newDbInstance.auths = this.serverConfig.db.auths;
    }
    // Add the instance to the list of approved db instances
    var allServerInstances = this.serverConfig.allServerInstances();
    // Add ourselves to all server callback instances
    for(var i = 0; i < allServerInstances.length; i++) {
      var server = allServerInstances[i];
      server.dbInstances.push(newDbInstance);
    }
    // Return new db object
    return newDbInstance;  
  }
  
  /**
   * Close the current db connection, including all the child db instances. Emits close event if no callback is provided.
   *
   * @param {Boolean} [forceClose] connection can never be reused.
   * @param {Function} callback this will be called after executing this method. The first parameter will contain the Error object if an error occured, or null otherwise. While the second parameter will contain the results or null if an error occured.
   * @return {null}
   * @api public
   */
  Db.prototype.close = function(forceClose, callback) {
    var self = this;
    // Ensure we force close all connections
    this._applicationClosed = false;
  
    if(typeof forceClose == 'function') {
      callback = forceClose;
    } else if(typeof forceClose == 'boolean') {
      this._applicationClosed = forceClose;
    }
  
    // Remove all listeners and close the connection
    this.serverConfig.close(function(err, result) {
      // Emit the close event
      if(typeof callback !== 'function') self.emit("close");
  
      // Emit close event across all db instances sharing the sockets
      var allServerInstances = self.serverConfig.allServerInstances();
      // Fetch the first server instance
      if(Array.isArray(allServerInstances) && allServerInstances.length > 0) {
        var server = allServerInstances[0];
        // For all db instances signal all db instances
        if(Array.isArray(server.dbInstances) && server.dbInstances.length > 1) {
          for(var i = 0; i < server.dbInstances.length; i++) {
            var dbInstance = server.dbInstances[i];
            // Check if it's our current db instance and skip if it is
            if(dbInstance.databaseName !== self.databaseName && dbInstance.tag !== self.tag) {
              server.dbInstances[i].emit("close");
            }
          }
        }
      }
  
      // Remove all listeners
      self.removeAllEventListeners();
      // You can reuse the db as everything is shut down
      self.openCalled = false;
      // If we have a callback call it
      if(callback) callback(err, result);
    });
  };
  
  /**
   * Access the Admin database
   *
   * @param {Function} [callback] returns the results.
   * @return {Admin} the admin db object.
   * @api public
   */
  Db.prototype.admin = function(callback) {
    if(callback == null) return new Admin(this);
    callback(null, new Admin(this));
  };
  
  /**
   * Returns a cursor to all the collection information.
   *
   * @param {String} [collectionName] the collection name we wish to retrieve the information from.
   * @param {Function} callback this will be called after executing this method. The first parameter will contain the Error object if an error occured, or null otherwise. While the second parameter will contain the options or null if an error occured.
   * @return {null}
   * @api public
   */
  Db.prototype.collectionsInfo = function(collectionName, callback) {
    if(callback == null && typeof collectionName == 'function') { callback = collectionName; collectionName = null; }
    // Create selector
    var selector = {};
    // If we are limiting the access to a specific collection name
    if(collectionName != null) selector.name = this.databaseName + "." + collectionName;
  
    // Return Cursor
    // callback for backward compatibility
    if(callback) {
      callback(null, new Cursor(this, new Collection(this, DbCommand.SYSTEM_NAMESPACE_COLLECTION), selector));
    } else {
      return new Cursor(this, new Collection(this, DbCommand.SYSTEM_NAMESPACE_COLLECTION), selector);
    }
  };
  
  /**
   * Get the list of all collection names for the specified db
   *
   * Options
   *  - **namesOnly** {String, default:false}, Return only the full collection namespace.
   *
   * @param {String} [collectionName] the collection name we wish to filter by.
   * @param {Object} [options] additional options during update.
   * @param {Function} callback this will be called after executing this method. The first parameter will contain the Error object if an error occured, or null otherwise. While the second parameter will contain the collection names or null if an error occured.
   * @return {null}
   * @api public
   */
  Db.prototype.collectionNames = function(collectionName, options, callback) {
    var self = this;
    var args = Array.prototype.slice.call(arguments, 0);
    callback = args.pop();
    collectionName = args.length ? args.shift() : null;
    options = args.length ? args.shift() : {};
  
    // Ensure no breaking behavior
    if(collectionName != null && typeof collectionName == 'object') {
      options = collectionName;
      collectionName = null;
    }
  
    // Let's make our own callback to reuse the existing collections info method
    self.collectionsInfo(collectionName, function(err, cursor) {
      if(err != null) return callback(err, null);
  
      cursor.toArray(function(err, documents) {
        if(err != null) return callback(err, null);
  
        // List of result documents that have been filtered
        var filtered_documents = documents.filter(function(document) {
          return !(document.name.indexOf(self.databaseName) == -1 || document.name.indexOf('$') != -1);
        });
  
        // If we are returning only the names
        if(options.namesOnly) {
          filtered_documents = filtered_documents.map(function(document) { return document.name });
        }
  
        // Return filtered items
        callback(null, filtered_documents);
      });
    });
  };
  
  /**
   * Fetch a specific collection (containing the actual collection information). If the application does not use strict mode you can
   * can use it without a callback in the following way. var collection = db.collection('mycollection');
   *
   * Options
  *  - **w**, {Number/String, > -1 || 'majority' || tag name} the write concern for the operation where < 1 is no acknowlegement of write and w >= 1, w = 'majority' or tag acknowledges the write
   *  - **wtimeout**, {Number, 0} set the timeout for waiting for write concern to finish (combines with w option)
   *  - **fsync**, (Boolean, default:false) write waits for fsync before returning
   *  - **journal**, (Boolean, default:false) write waits for journal sync before returning
   *  - **serializeFunctions** {Boolean, default:false}, serialize functions on the document.
   *  - **raw** {Boolean, default:false}, perform all operations using raw bson objects.
   *  - **pkFactory** {Object}, object overriding the basic ObjectID primary key generation.
   *  - **readPreference** {String}, the prefered read preference (ReadPreference.PRIMARY, ReadPreference.PRIMARY_PREFERRED, ReadPreference.SECONDARY, ReadPreference.SECONDARY_PREFERRED, ReadPreference.NEAREST).
   *  - **strict**, (Boolean, default:false) throws and error if the collection does not exist
   * 
   * Deprecated Options 
   *  - **safe** {true | {w:n, wtimeout:n} | {fsync:true}, default:false}, executes with a getLastError command returning the results of the command on MongoDB.
   *
   * @param {String} collectionName the collection name we wish to access.
   * @param {Object} [options] returns option results.
   * @param {Function} callback this will be called after executing this method. The first parameter will contain the Error object if an error occured, or null otherwise. While the second parameter will contain the collection or null if an error occured.
   * @return {null}
   * @api public
   */
  Db.prototype.collection = function(collectionName, options, callback) {
    var self = this;
    if(typeof options === "function") { callback = options; options = {}; }
    // Execute safe
  
    if(options && (options.strict)) {
      self.collectionNames(collectionName, function(err, collections) {
        if(err != null) return callback(err, null);
  
        if(collections.length == 0) {
          return callback(new Error("Collection " + collectionName + " does not exist. Currently in safe mode."), null);
        } else {
          try {
            var collection = new Collection(self, collectionName, self.pkFactory, options);
          } catch(err) {
            return callback(err, null);
          }
          return callback(null, collection);
        }
      });
    } else {
      try {
        var collection = new Collection(self, collectionName, self.pkFactory, options);
      } catch(err) {
        if(callback == null) {
          throw err;
        } else {
          return callback(err, null);
        }
      }
  
      // If we have no callback return collection object
      return callback == null ? collection : callback(null, collection);
    }
  };
  
  /**
   * Fetch all collections for the current db.
   *
   * @param {Function} callback this will be called after executing this method. The first parameter will contain the Error object if an error occured, or null otherwise. While the second parameter will contain the collections or null if an error occured.
   * @return {null}
   * @api public
   */
  Db.prototype.collections = function(callback) {
    var self = this;
    // Let's get the collection names
    self.collectionNames(function(err, documents) {
      if(err != null) return callback(err, null);
      var collections = [];
      documents.forEach(function(document) {
        collections.push(new Collection(self, document.name.replace(self.databaseName + ".", ''), self.pkFactory));
      });
      // Return the collection objects
      callback(null, collections);
    });
  };
  
  /**
   * Evaluate javascript on the server
   *
   * Options
   *  - **nolock** {Boolean, default:false}, Tell MongoDB not to block on the evaulation of the javascript.
   *
   * @param {Code} code javascript to execute on server.
   * @param {Object|Array} [parameters] the parameters for the call.
   * @param {Object} [options] the options
   * @param {Function} callback this will be called after executing this method. The first parameter will contain the Error object if an error occured, or null otherwise. While the second parameter will contain the results from eval or null if an error occured.
   * @return {null}
   * @api public
   */
  Db.prototype.eval = function(code, parameters, options, callback) {
    // Unpack calls
    var args = Array.prototype.slice.call(arguments, 1);
    callback = args.pop();
    parameters = args.length ? args.shift() : parameters;
    options = args.length ? args.shift() : {};
  
    var finalCode = code;
    var finalParameters = [];
    // If not a code object translate to one
    if(!(finalCode instanceof this.bsonLib.Code)) {
      finalCode = new this.bsonLib.Code(finalCode);
    }
  
    // Ensure the parameters are correct
    if(parameters != null && parameters.constructor != Array && typeof parameters !== 'function') {
      finalParameters = [parameters];
    } else if(parameters != null && parameters.constructor == Array && typeof parameters !== 'function') {
      finalParameters = parameters;
    }
  
    // Create execution selector
    var selector = {'$eval':finalCode, 'args':finalParameters};
    // Check if the nolock parameter is passed in
    if(options['nolock']) {
      selector['nolock'] = options['nolock'];
    }
  
    // Set primary read preference
    options.readPreference = ReadPreference.PRIMARY;
  
    // Execute the eval
    this.collection(DbCommand.SYSTEM_COMMAND_COLLECTION).findOne(selector, options, function(err, result) {
      if(err) return callback(err);
  
      if(result && result.ok == 1) {
        callback(null, result.retval);
      } else if(result) {
        callback(new Error("eval failed: " + result.errmsg), null); return;
      } else {
        callback(err, result);
      }
    });
  };
  
  /**
   * Dereference a dbref, against a db
   *
   * @param {DBRef} dbRef db reference object we wish to resolve.
   * @param {Function} callback this will be called after executing this method. The first parameter will contain the Error object if an error occured, or null otherwise. While the second parameter will contain the results from dereference or null if an error occured.
   * @return {null}
   * @api public
   */
  Db.prototype.dereference = function(dbRef, callback) {
    var db = this;
    // If we have a db reference then let's get the db first
    if(dbRef.db != null) db = this.db(dbRef.db);
    // Fetch the collection and find the reference
    var collection = db.collection(dbRef.namespace);
    collection.findOne({'_id':dbRef.oid}, function(err, result) {
      callback(err, result);
    });
  };
  
  /**
   * Logout user from server, fire off on all connections and remove all auth info
   *
   * @param {Function} callback this will be called after executing this method. The first parameter will contain the Error object if an error occured, or null otherwise. While the second parameter will contain the results from logout or null if an error occured.
   * @return {null}
   * @api public
   */
  Db.prototype.logout = function(options, callback) {
    var self = this;
    // Unpack calls
    var args = Array.prototype.slice.call(arguments, 0);
    callback = args.pop();
    options = args.length ? args.shift() : {};
  
    // Number of connections we need to logout from
    var numberOfConnections = this.serverConfig.allRawConnections().length;
  
    // Let's generate the logout command object
    var logoutCommand = DbCommand.logoutCommand(self, {logout:1}, options);
    self._executeQueryCommand(logoutCommand, {onAll:true}, function(err, result) {
      // Count down
      numberOfConnections = numberOfConnections - 1;
      // Work around the case where the number of connections are 0
      if(numberOfConnections <= 0 && typeof callback == 'function') {
        var internalCallback = callback;
        callback = null;
        // Reset auth
        self.auths = [];
        // Handle any errors
        if(err == null && result.documents[0].ok == 1) {
          internalCallback(null, true);
        } else {
          err != null ? internalCallback(err, false) : internalCallback(new Error(result.documents[0].errmsg), false);
        }
      }
    });
  }
  
  /**
   * Authenticate a user against the server.
   *
   * Options
   *  - **authSource** {String}, The database that the credentials are for,
   *    different from the name of the current DB, for example admin
   *
   * @param {String} username username.
   * @param {String} password password.
   * @param {Object} [options] the options
   * @param {Function} callback this will be called after executing this method. The first parameter will contain the Error object if an error occured, or null otherwise. While the second parameter will contain the results from authentication or null if an error occured.
   * @return {null}
   * @api public
   */
  Db.prototype.authenticate = function(username, password, options, callback) {
    var self = this;
  
    if (typeof callback === 'undefined') {
      callback = options;
      options = {};
    }
    // the default db to authenticate against is 'this'
    // if authententicate is called from a retry context, it may be another one, like admin
    var authdb = options.authdb ? options.authdb : self.databaseName;
    authdb = options.authSource ? options.authSource : authdb;
    // Push the new auth if we have no previous record
    
    var numberOfConnections = 0;
    var errorObject = null;
  
    if(options['connection'] != null) {
      //if a connection was explicitly passed on options, then we have only one...
      numberOfConnections = 1;
    } else {
      // Get the amount of connections in the pool to ensure we have authenticated all comments
      numberOfConnections = this.serverConfig.allRawConnections().length;
      options['onAll'] = true;
    }
  
    // Execute all four
    this._executeQueryCommand(DbCommand.createGetNonceCommand(self), options, function(err, result, connection) {
      // Execute on all the connections
      if(err == null) {
        // Nonce used to make authentication request with md5 hash
        var nonce = result.documents[0].nonce;
        // Execute command
        self._executeQueryCommand(DbCommand.createAuthenticationCommand(self, username, password, nonce, authdb), {connection:connection}, function(err, result) {
          // Count down
          numberOfConnections = numberOfConnections - 1;
          // Ensure we save any error
          if(err) {
            errorObject = err;
          } else if(result.documents[0].err != null || result.documents[0].errmsg != null){
            errorObject = utils.toError(result.documents[0]);
          }
  
          // Work around the case where the number of connections are 0
          if(numberOfConnections <= 0 && typeof callback == 'function') {
            var internalCallback = callback;
            callback = null;
  
            if(errorObject == null && result.documents[0].ok == 1) {
              // We authenticated correctly save the credentials
              self.auths = [{'username':username, 'password':password, 'authdb': authdb}];
              // Return callback
              internalCallback(errorObject, true);
            } else {
              internalCallback(errorObject, false);
            }
          }
        });
      }
    });
  };
  
  /**
   * Add a user to the database.
   *
   * Options
   *  - **w**, {Number/String, > -1 || 'majority' || tag name} the write concern for the operation where < 1 is no acknowlegement of write and w >= 1, w = 'majority' or tag acknowledges the write
   *  - **wtimeout**, {Number, 0} set the timeout for waiting for write concern to finish (combines with w option)
   *  - **fsync**, (Boolean, default:false) write waits for fsync before returning
   *  - **journal**, (Boolean, default:false) write waits for journal sync before returning
   * 
   * Deprecated Options 
   *  - **safe** {true | {w:n, wtimeout:n} | {fsync:true}, default:false}, executes with a getLastError command returning the results of the command on MongoDB.
   *
   * @param {String} username username.
   * @param {String} password password.
   * @param {Object} [options] additional options during update.
   * @param {Function} callback this will be called after executing this method. The first parameter will contain the Error object if an error occured, or null otherwise. While the second parameter will contain the results from addUser or null if an error occured.
   * @return {null}
   * @api public
   */
  Db.prototype.addUser = function(username, password, options, callback) {
    var self = this;
    var args = Array.prototype.slice.call(arguments, 2);
    callback = args.pop();
    options = args.length ? args.shift() : {};
  
    // Get the error options
    var errorOptions = _getWriteConcern(this, options, callback);
    errorOptions.w = errorOptions.w == null ? 1 : errorOptions.w;
    // Use node md5 generator
    var md5 = crypto.createHash('md5');
    // Generate keys used for authentication
    md5.update(username + ":mongo:" + password);
    var userPassword = md5.digest('hex');
    // Fetch a user collection
    var collection = this.collection(DbCommand.SYSTEM_USER_COLLECTION);
    // Check if we are inserting the first user
    collection.count({}, function(err, count) {
      // We got an error (f.ex not authorized)
      if(err != null) return callback(err, null);
      // Check if the user exists and update i
      collection.find({user: username}, {dbName: options['dbName']}).toArray(function(err, documents) {
        // We got an error (f.ex not authorized)
        if(err != null) return callback(err, null);
        // Add command keys
        var commandOptions = errorOptions;
        commandOptions.dbName = options['dbName'];
        commandOptions.upsert = true;
  
        // We have a user, let's update the password or upsert if not
        collection.update({user: username},{$set: {user: username, pwd: userPassword}}, commandOptions, function(err, results) {
          if(count == 0 && err) {
            callback(null, [{user:username, pwd:userPassword}]);
          } else if(err) {
            callback(err, null)
          } else {
            callback(null, [{user:username, pwd:userPassword}]);
          }
        });
      });
    });
  };
  
  /**
   * Remove a user from a database
   *
   * Options
  *  - **w**, {Number/String, > -1 || 'majority' || tag name} the write concern for the operation where < 1 is no acknowlegement of write and w >= 1, w = 'majority' or tag acknowledges the write
   *  - **wtimeout**, {Number, 0} set the timeout for waiting for write concern to finish (combines with w option)
   *  - **fsync**, (Boolean, default:false) write waits for fsync before returning
   *  - **journal**, (Boolean, default:false) write waits for journal sync before returning
   * 
   * Deprecated Options 
   *  - **safe** {true | {w:n, wtimeout:n} | {fsync:true}, default:false}, executes with a getLastError command returning the results of the command on MongoDB.
   *
   * @param {String} username username.
   * @param {Object} [options] additional options during update.
   * @param {Function} callback this will be called after executing this method. The first parameter will contain the Error object if an error occured, or null otherwise. While the second parameter will contain the results from removeUser or null if an error occured.
   * @return {null}
   * @api public
   */
  Db.prototype.removeUser = function(username, options, callback) {
    var self = this;
    var args = Array.prototype.slice.call(arguments, 1);
    callback = args.pop();
    options = args.length ? args.shift() : {};
  
    // Figure out the safe mode settings
    var safe = self.safe != null && self.safe == false ? {w: 1} : self.safe;
    // Override with options passed in if applicable
    safe = options != null && options['safe'] != null ? options['safe'] : safe;
    // Ensure it's at least set to safe
    safe = safe == null ? {w: 1} : safe;
  
    // Fetch a user collection
    var collection = this.collection(DbCommand.SYSTEM_USER_COLLECTION);
    collection.findOne({user: username}, {dbName: options['dbName']}, function(err, user) {
      if(user != null) {
        // Add command keys
        var commandOptions = safe;
        commandOptions.dbName = options['dbName'];
  
        collection.remove({user: username}, commandOptions, function(err, result) {
          callback(err, true);
        });
      } else {
        callback(err, false);
      }
    });
  };
  
  /**
   * Creates a collection on a server pre-allocating space, need to create f.ex capped collections.
   *
   * Options
  *  - **w**, {Number/String, > -1 || 'majority' || tag name} the write concern for the operation where < 1 is no acknowlegement of write and w >= 1, w = 'majority' or tag acknowledges the write
   *  - **wtimeout**, {Number, 0} set the timeout for waiting for write concern to finish (combines with w option)
   *  - **fsync**, (Boolean, default:false) write waits for fsync before returning
   *  - **journal**, (Boolean, default:false) write waits for journal sync before returning
   *  - **serializeFunctions** {Boolean, default:false}, serialize functions on the document.
   *  - **raw** {Boolean, default:false}, perform all operations using raw bson objects.
   *  - **pkFactory** {Object}, object overriding the basic ObjectID primary key generation.
   *  - **capped** {Boolean, default:false}, create a capped collection.
   *  - **size** {Number}, the size of the capped collection in bytes.
   *  - **max** {Number}, the maximum number of documents in the capped collection.
   *  - **autoIndexId** {Boolean, default:true}, create an index on the _id field of the document, True by default on MongoDB 2.2 or higher off for version < 2.2.
   *  - **readPreference** {String}, the prefered read preference (ReadPreference.PRIMARY, ReadPreference.PRIMARY_PREFERRED, ReadPreference.SECONDARY, ReadPreference.SECONDARY_PREFERRED, ReadPreference.NEAREST).
   *  - **strict**, (Boolean, default:false) throws and error if collection already exists
   * 
   * Deprecated Options 
   *  - **safe** {true | {w:n, wtimeout:n} | {fsync:true}, default:false}, executes with a getLastError command returning the results of the command on MongoDB.
   *
   * @param {String} collectionName the collection name we wish to access.
   * @param {Object} [options] returns option results.
   * @param {Function} callback this will be called after executing this method. The first parameter will contain the Error object if an error occured, or null otherwise. While the second parameter will contain the results from createCollection or null if an error occured.
   * @return {null}
   * @api public
   */
  Db.prototype.createCollection = function(collectionName, options, callback) {
    var args = Array.prototype.slice.call(arguments, 1);
    callback = args.pop();
    options = args.length ? args.shift() : null;
    var self = this;
  
    // Figure out the safe mode settings
    var safe = self.safe != null && self.safe == false ? {w: 1} : self.safe;
    // Override with options passed in if applicable
    safe = options != null && options['safe'] != null ? options['safe'] : safe;
    // Ensure it's at least set to safe
    safe = safe == null ? {w: 1} : safe;
  
    // Check if we have the name
    this.collectionNames(collectionName, function(err, collections) {
      if(err != null) return callback(err, null);
  
      var found = false;
      collections.forEach(function(collection) {
        if(collection.name == self.databaseName + "." + collectionName) found = true;
      });
  
      // If the collection exists either throw an exception (if db in safe mode) or return the existing collection
      if(found && options && options.strict) {
        return callback(new Error("Collection " + collectionName + " already exists. Currently in safe mode."), null);
      } else if(found){
        try {
          var collection = new Collection(self, collectionName, self.pkFactory, options);
        } catch(err) {
          return callback(err, null);
        }
        return callback(null, collection);
      }
  
      // Create a new collection and return it
      self._executeQueryCommand(DbCommand.createCreateCollectionCommand(self, collectionName, options), {read:false, safe:safe}, function(err, result) {
        var document = result.documents[0];
        // If we have no error let's return the collection
        if(err == null && document.ok == 1) {
          try {
            var collection = new Collection(self, collectionName, self.pkFactory, options);
          } catch(err) {
            return callback(err, null);
          }
          return callback(null, collection);
        } else {
          if (null == err) err = utils.toError(document);
          callback(err, null);
        }
      });
    });
  };
  
  /**
   * Execute a command hash against MongoDB. This lets you acess any commands not available through the api on the server.
   *
   * @param {Object} selector the command hash to send to the server, ex: {ping:1}.
   * @param {Function} callback this will be called after executing this method. The command always return the whole result of the command as the second parameter.
   * @return {null}
   * @api public
   */
  Db.prototype.command = function(selector, options, callback) {
    var args = Array.prototype.slice.call(arguments, 1);
    callback = args.pop();
    options = args.length ? args.shift() : {};
  
    // Set up the options
    var cursor = new Cursor(this
      , new Collection(this, DbCommand.SYSTEM_COMMAND_COLLECTION), selector, {}, {
        limit: -1, timeout: QueryCommand.OPTS_NO_CURSOR_TIMEOUT, dbName: options['dbName']
      });
  
    // Set read preference if we set one
    var readPreference = options['readPreference'] ? options['readPreference'] : false;
  
    // Ensure only commands who support read Prefrences are exeuted otherwise override and use Primary
    if(readPreference != false) {
      if(selector['group'] || selector['aggregate'] || selector['collStats'] || selector['dbStats']
        || selector['count'] || selector['distinct'] || selector['geoNear'] || selector['geoSearch'] || selector['geoWalk']
        || (selector['mapreduce'] && selector.out == 'inline')) {
        // Set the read preference
        cursor.setReadPreference(readPreference);
      } else {
        cursor.setReadPreference(ReadPreference.PRIMARY);
      }
    }
  
    // Return the next object
    cursor.nextObject(callback);
  };
  
  /**
   * Drop a collection from the database, removing it permanently. New accesses will create a new collection.
   *
   * @param {String} collectionName the name of the collection we wish to drop.
   * @param {Function} callback this will be called after executing this method. The first parameter will contain the Error object if an error occured, or null otherwise. While the second parameter will contain the results from dropCollection or null if an error occured.
   * @return {null}
   * @api public
   */
  Db.prototype.dropCollection = function(collectionName, callback) {
    var self = this;
    callback || (callback = function(){});
  
    // Drop the collection
    this._executeQueryCommand(DbCommand.createDropCollectionCommand(this, collectionName), function(err, result) {
      if(err == null && result.documents[0].ok == 1) {
        return callback(null, true);
      }
  
      if(null == err) err = utils.toError(result.documents[0]);
      callback(err, null);
    });
  };
  
  /**
   * Rename a collection.
   * 
   * Options
   *  - **dropTarget** {Boolean, default:false}, drop the target name collection if it previously exists.
   *
   * @param {String} fromCollection the name of the current collection we wish to rename.
   * @param {String} toCollection the new name of the collection.
   * @param {Object} [options] returns option results.
   * @param {Function} callback this will be called after executing this method. The first parameter will contain the Error object if an error occured, or null otherwise. While the second parameter will contain the results from renameCollection or null if an error occured.
   * @return {null}
   * @api public
   */
  Db.prototype.renameCollection = function(fromCollection, toCollection, options, callback) {
    var self = this;
  
    if(typeof options == 'function') {
      callback = options;
      options = {}
    }
  
    callback || (callback = function(){});
    // Execute the command, return the new renamed collection if successful
    this._executeQueryCommand(DbCommand.createRenameCollectionCommand(this, fromCollection, toCollection, options), function(err, result) {
      if(err == null && result.documents[0].ok == 1) {
        return callback(null, new Collection(self, toCollection, self.pkFactory));
      }
  
      if(null == err) err = utils.toError(result.documents[0]);
      callback(err, null);
    });
  };
  
  /**
   * Return last error message for the given connection, note options can be combined.
   *
   * Options
   *  - **fsync** {Boolean, default:false}, option forces the database to fsync all files before returning.
   *  - **j** {Boolean, default:false}, awaits the journal commit before returning, > MongoDB 2.0.
   *  - **w** {Number}, until a write operation has been replicated to N servers.
   *  - **wtimeout** {Number}, number of miliseconds to wait before timing out.
   *
   * Connection Options
   *  - **connection** {Connection}, fire the getLastError down a specific connection.
   *
   * @param {Object} [options] returns option results.
   * @param {Object} [connectionOptions] returns option results.
   * @param {Function} callback this will be called after executing this method. The first parameter will contain the Error object if an error occured, or null otherwise. While the second parameter will contain the results from lastError or null if an error occured.
   * @return {null}
   * @api public
   */
  Db.prototype.lastError = function(options, connectionOptions, callback) {
    // Unpack calls
    var args = Array.prototype.slice.call(arguments, 0);
    callback = args.pop();
    options = args.length ? args.shift() : {};
    connectionOptions = args.length ? args.shift() : {};
  
    this._executeQueryCommand(DbCommand.createGetLastErrorCommand(options, this), connectionOptions, function(err, error) {
      callback(err, error && error.documents);
    });
  };
  
  /**
   * Legacy method calls.
   *
   * @ignore
   * @api private
   */
  Db.prototype.error = Db.prototype.lastError;
  Db.prototype.lastStatus = Db.prototype.lastError;
  
  /**
   * Return all errors up to the last time db reset_error_history was called.
   *
   * Options
   *  - **connection** {Connection}, fire the getLastError down a specific connection.
   *
   * @param {Object} [options] returns option results.
   * @param {Function} callback this will be called after executing this method. The first parameter will contain the Error object if an error occured, or null otherwise. While the second parameter will contain the results from previousErrors or null if an error occured.
   * @return {null}
   * @api public
   */
  Db.prototype.previousErrors = function(options, callback) {
    // Unpack calls
    var args = Array.prototype.slice.call(arguments, 0);
    callback = args.pop();
    options = args.length ? args.shift() : {};
  
    this._executeQueryCommand(DbCommand.createGetPreviousErrorsCommand(this), options, function(err, error) {
      callback(err, error.documents);
    });
  };
  
  /**
   * Runs a command on the database.
   * @ignore
   * @api private
   */
  Db.prototype.executeDbCommand = function(command_hash, options, callback) {
    if(callback == null) { callback = options; options = {}; }
    this._executeQueryCommand(DbCommand.createDbSlaveOkCommand(this, command_hash, options), options, callback);
  };
  
  /**
   * Runs a command on the database as admin.
   * @ignore
   * @api private
   */
  Db.prototype.executeDbAdminCommand = function(command_hash, options, callback) {
    if(callback == null) { callback = options; options = {}; }
    this._executeQueryCommand(DbCommand.createAdminDbCommand(this, command_hash), options, callback);
  };
  
  /**
   * Resets the error history of the mongo instance.
   *
   * Options
   *  - **connection** {Connection}, fire the getLastError down a specific connection.
   *
   * @param {Object} [options] returns option results.
   * @param {Function} callback this will be called after executing this method. The first parameter will contain the Error object if an error occured, or null otherwise. While the second parameter will contain the results from resetErrorHistory or null if an error occured.
   * @return {null}
   * @api public
   */
  Db.prototype.resetErrorHistory = function(options, callback) {
    // Unpack calls
    var args = Array.prototype.slice.call(arguments, 0);
    callback = args.pop();
    options = args.length ? args.shift() : {};
  
    this._executeQueryCommand(DbCommand.createResetErrorHistoryCommand(this), options, function(err, error) {
      callback(err, error.documents);
    });
  };
  
  /**
   * Creates an index on the collection.
   *
   * Options
  *  - **w**, {Number/String, > -1 || 'majority' || tag name} the write concern for the operation where < 1 is no acknowlegement of write and w >= 1, w = 'majority' or tag acknowledges the write
   *  - **wtimeout**, {Number, 0} set the timeout for waiting for write concern to finish (combines with w option)
   *  - **fsync**, (Boolean, default:false) write waits for fsync before returning
   *  - **journal**, (Boolean, default:false) write waits for journal sync before returning
   *  - **unique** {Boolean, default:false}, creates an unique index.
   *  - **sparse** {Boolean, default:false}, creates a sparse index.
   *  - **background** {Boolean, default:false}, creates the index in the background, yielding whenever possible.
   *  - **dropDups** {Boolean, default:false}, a unique index cannot be created on a key that has pre-existing duplicate values. If you would like to create the index anyway, keeping the first document the database indexes and deleting all subsequent documents that have duplicate value
   *  - **min** {Number}, for geospatial indexes set the lower bound for the co-ordinates.
   *  - **max** {Number}, for geospatial indexes set the high bound for the co-ordinates.
   *  - **v** {Number}, specify the format version of the indexes.
   *  - **expireAfterSeconds** {Number}, allows you to expire data on indexes applied to a data (MongoDB 2.2 or higher)
   *  - **name** {String}, override the autogenerated index name (useful if the resulting name is larger than 128 bytes)
   * 
   * Deprecated Options 
   *  - **safe** {true | {w:n, wtimeout:n} | {fsync:true}, default:false}, executes with a getLastError command returning the results of the command on MongoDB.
   *
   *
   * @param {String} collectionName name of the collection to create the index on.
   * @param {Object} fieldOrSpec fieldOrSpec that defines the index.
   * @param {Object} [options] additional options during update.
   * @param {Function} callback this will be called after executing this method. The first parameter will contain the Error object if an error occured, or null otherwise. While the second parameter will contain the results from createIndex or null if an error occured.
   * @return {null}
   * @api public
   */
  Db.prototype.createIndex = function(collectionName, fieldOrSpec, options, callback) {
    var self = this;
    var args = Array.prototype.slice.call(arguments, 2);
    callback = args.pop();
    options = args.length ? args.shift() : {};
    options = typeof callback === 'function' ? options : callback;
    options = options == null ? {} : options;
  
    // Get the error options
    var errorOptions = _getWriteConcern(this, options, callback);
    // Create command
    var command = DbCommand.createCreateIndexCommand(this, collectionName, fieldOrSpec, options);
    // Default command options
    var commandOptions = {};
  
    // If we have error conditions set handle them
    if(_hasWriteConcern(errorOptions) && typeof callback == 'function') {
      // Insert options
      commandOptions['read'] = false;
      // If we have safe set set async to false
      if(errorOptions == null) commandOptions['async'] = true;
  
      // Set safe option
      commandOptions['safe'] = errorOptions;
      // If we have an error option
      if(typeof errorOptions == 'object') {
        var keys = Object.keys(errorOptions);
        for(var i = 0; i < keys.length; i++) {
          commandOptions[keys[i]] = errorOptions[keys[i]];
        }
      }
  
      // Execute insert command
      this._executeInsertCommand(command, commandOptions, function(err, result) {
        if(err != null) return callback(err, null);
  
        result = result && result.documents;
        if (result[0].err) {
          callback(utils.toError(result[0]));
        } else {
          callback(null, command.documents[0].name);
        }
      });
    } else if(_hasWriteConcern(errorOptions) && callback == null) {
      throw new Error("Cannot use a writeConcern without a provided callback");
    } else {
      // Execute insert command
      var result = this._executeInsertCommand(command, commandOptions);
      // If no callback just return
      if(!callback) return;
      // If error return error
      if(result instanceof Error) {
        return callback(result);
      }
      // Otherwise just return
      return callback(null, null);
    }
  };
  
  /**
   * Ensures that an index exists, if it does not it creates it
   *
   * Options
  *  - **w**, {Number/String, > -1 || 'majority' || tag name} the write concern for the operation where < 1 is no acknowlegement of write and w >= 1, w = 'majority' or tag acknowledges the write
   *  - **wtimeout**, {Number, 0} set the timeout for waiting for write concern to finish (combines with w option)
   *  - **fsync**, (Boolean, default:false) write waits for fsync before returning
   *  - **journal**, (Boolean, default:false) write waits for journal sync before returning
   *  - **unique** {Boolean, default:false}, creates an unique index.
   *  - **sparse** {Boolean, default:false}, creates a sparse index.
   *  - **background** {Boolean, default:false}, creates the index in the background, yielding whenever possible.
   *  - **dropDups** {Boolean, default:false}, a unique index cannot be created on a key that has pre-existing duplicate values. If you would like to create the index anyway, keeping the first document the database indexes and deleting all subsequent documents that have duplicate value
   *  - **min** {Number}, for geospatial indexes set the lower bound for the co-ordinates.
   *  - **max** {Number}, for geospatial indexes set the high bound for the co-ordinates.
   *  - **v** {Number}, specify the format version of the indexes.
   *  - **expireAfterSeconds** {Number}, allows you to expire data on indexes applied to a data (MongoDB 2.2 or higher)
   *  - **name** {String}, override the autogenerated index name (useful if the resulting name is larger than 128 bytes)
   * 
   * Deprecated Options 
   *  - **safe** {true | {w:n, wtimeout:n} | {fsync:true}, default:false}, executes with a getLastError command returning the results of the command on MongoDB.
   *
   * @param {String} collectionName name of the collection to create the index on.
   * @param {Object} fieldOrSpec fieldOrSpec that defines the index.
   * @param {Object} [options] additional options during update.
   * @param {Function} callback this will be called after executing this method. The first parameter will contain the Error object if an error occured, or null otherwise. While the second parameter will contain the results from ensureIndex or null if an error occured.
   * @return {null}
   * @api public
   */
  Db.prototype.ensureIndex = function(collectionName, fieldOrSpec, options, callback) {
    var self = this;
  
    if (typeof callback === 'undefined' && typeof options === 'function') {
      callback = options;
      options = {};
    }
  
    if (options == null) {
      options = {};
    }
  
    // Get the error options
    var errorOptions = _getWriteConcern(this, options, callback);
    // Make sure we don't try to do a write concern without a callback
    if(_hasWriteConcern(errorOptions) && callback == null)
      throw new Error("Cannot use a writeConcern without a provided callback");
    // Create command
    var command = DbCommand.createCreateIndexCommand(this, collectionName, fieldOrSpec, options);
    var index_name = command.documents[0].name;
  
    // Default command options
    var commandOptions = {};
    // Check if the index allready exists
    this.indexInformation(collectionName, function(err, collectionInfo) {
      if(err != null) return callback(err, null);
  
      if(!collectionInfo[index_name])  {
        // If we have error conditions set handle them
        if(_hasWriteConcern(errorOptions) && typeof callback == 'function') {
          // Insert options
          commandOptions['read'] = false;
          // If we have safe set set async to false
          if(errorOptions == null) commandOptions['async'] = true;
  
          // If we have an error option
          if(typeof errorOptions == 'object') {
            var keys = Object.keys(errorOptions);
            for(var i = 0; i < keys.length; i++) {
              commandOptions[keys[i]] = errorOptions[keys[i]];
            }
          }
  
          if(typeof callback === 'function' 
            && commandOptions.w < 1 && !commandOptions.fsync && !commandOptions.journal) {
            commandOptions.w = 1;
          }
  
          self._executeInsertCommand(command, commandOptions, function(err, result) {
            // Only callback if we have one specified
            if(typeof callback === 'function') {
              if(err != null) return callback(err, null);
  
              result = result && result.documents;
              if (result[0].err) {
                callback(utils.toError(result[0]));
              } else {
                callback(null, command.documents[0].name);
              }
            }
          });
        } else {
          // Execute insert command
          var result = self._executeInsertCommand(command, commandOptions);
          // If no callback just return
          if(!callback) return;
          // If error return error
          if(result instanceof Error) {
            return callback(result);
          }
          // Otherwise just return
          return callback(null, index_name);
        }
      } else {
        if(typeof callback === 'function') return callback(null, index_name);
      }
    });
  };
  
  /**
   * Returns the information available on allocated cursors.
   *
   * Options
   *  - **readPreference** {String}, the prefered read preference (ReadPreference.PRIMARY, ReadPreference.PRIMARY_PREFERRED, ReadPreference.SECONDARY, ReadPreference.SECONDARY_PREFERRED, ReadPreference.NEAREST).
   *
   * @param {Object} [options] additional options during update.
   * @param {Function} callback this will be called after executing this method. The first parameter will contain the Error object if an error occured, or null otherwise. While the second parameter will contain the results from cursorInfo or null if an error occured.
   * @return {null}
   * @api public
   */
  Db.prototype.cursorInfo = function(options, callback) {
    var args = Array.prototype.slice.call(arguments, 0);
    callback = args.pop();
    options = args.length ? args.shift() : {};
  
    this._executeQueryCommand(DbCommand.createDbSlaveOkCommand(this, {'cursorInfo':1}), options, function(err, result) {
      callback(err, result.documents[0]);
    });
  };
  
  /**
   * Drop an index on a collection.
   *
   * @param {String} collectionName the name of the collection where the command will drop an index.
   * @param {String} indexName name of the index to drop.
   * @param {Function} callback this will be called after executing this method. The first parameter will contain the Error object if an error occured, or null otherwise. While the second parameter will contain the results from dropIndex or null if an error occured.
   * @return {null}
   * @api public
   */
  Db.prototype.dropIndex = function(collectionName, indexName, callback) {  
    this._executeQueryCommand(DbCommand.createDropIndexCommand(this, collectionName, indexName), callback);
  };
  
  /**
   * Reindex all indexes on the collection
   * Warning: reIndex is a blocking operation (indexes are rebuilt in the foreground) and will be slow for large collections.
   *
   * @param {String} collectionName the name of the collection.
   * @param {Function} callback this will be called after executing this method. The first parameter will contain the Error object if an error occured, or null otherwise. While the second parameter will contain the results from reIndex or null if an error occured.
   * @api public
  **/
  Db.prototype.reIndex = function(collectionName, callback) {
    this._executeQueryCommand(DbCommand.createReIndexCommand(this, collectionName), function(err, result) {
      if(err != null) {
        callback(err, false);
      } else if(result.documents[0].errmsg == null) {
        callback(null, true);
      } else {
        callback(new Error(result.documents[0].errmsg), false);
      }
    });
  };
  
  /**
   * Retrieves this collections index info.
   *
   * Options
   *  - **full** {Boolean, default:false}, returns the full raw index information.
   *  - **readPreference** {String}, the preferred read preference ((Server.PRIMARY, Server.PRIMARY_PREFERRED, Server.SECONDARY, Server.SECONDARY_PREFERRED, Server.NEAREST).
   *
   * @param {String} collectionName the name of the collection.
   * @param {Object} [options] additional options during update.
   * @param {Function} callback this will be called after executing this method. The first parameter will contain the Error object if an error occured, or null otherwise. While the second parameter will contain the results from indexInformation or null if an error occured.
   * @return {null}
   * @api public
   */
  Db.prototype.indexInformation = function(collectionName, options, callback) {
    if(typeof callback === 'undefined') {
      if(typeof options === 'undefined') {
        callback = collectionName;
        collectionName = null;
      } else {
        callback = options;
      }
      options = {};
    }
  
    // If we specified full information
    var full = options['full'] == null ? false : options['full'];
    // Build selector for the indexes
    var selector = collectionName != null ? {ns: (this.databaseName + "." + collectionName)} : {};
  
    // Set read preference if we set one
    var readPreference = options['readPreference'] ? options['readPreference'] : ReadPreference.PRIMARY;
  
    // Iterate through all the fields of the index
    this.collection(DbCommand.SYSTEM_INDEX_COLLECTION, function(err, collection) {
      // Perform the find for the collection
      collection.find(selector).setReadPreference(readPreference).toArray(function(err, indexes) {
        if(err != null) return callback(err, null);
        // Contains all the information
        var info = {};
  
        // if full defined just return all the indexes directly
        if(full) return callback(null, indexes);
  
        // Process all the indexes
        for(var i = 0; i < indexes.length; i++) {
          var index = indexes[i];
          // Let's unpack the object
          info[index.name] = [];
          for(var name in index.key) {
            info[index.name].push([name, index.key[name]]);
          }
        }
  
        // Return all the indexes
        callback(null, info);
      });
    });
  };
  
  /**
   * Drop a database.
   *
   * @param {Function} callback this will be called after executing this method. The first parameter will contain the Error object if an error occured, or null otherwise. While the second parameter will contain the results from dropDatabase or null if an error occured.
   * @return {null}
   * @api public
   */
  Db.prototype.dropDatabase = function(callback) {
    var self = this;
  
    this._executeQueryCommand(DbCommand.createDropDatabaseCommand(this), function(err, result) {
      if(err == null && result.documents[0].ok == 1) {
        callback(null, true);
      } else {
        if(err) {
          callback(err, false);
        } else {
          callback(utils.toError(result.documents[0]), false);
        }
      }
    });
  };
  
  /**
   * Get all the db statistics.
   *
   * Options
   *  - **scale** {Number}, divide the returned sizes by scale value.
   *  - **readPreference** {String}, the preferred read preference ((Server.PRIMARY, Server.PRIMARY_PREFERRED, Server.SECONDARY, Server.SECONDARY_PREFERRED, Server.NEAREST).
   *
   * @param {Objects} [options] options for the stats command
   * @param {Function} callback this will be called after executing this method. The first parameter will contain the Error object if an error occured, or null otherwise. While the second parameter will contain the results from stats or null if an error occured.
   * @return {null}
   * @api public
   */
  Db.prototype.stats = function stats(options, callback) {
    var args = Array.prototype.slice.call(arguments, 0);
    callback = args.pop();
    // Fetch all commands
    options = args.length ? args.shift() : {};
  
    // Build command object
    var commandObject = {
      dbStats:this.collectionName,
    }
  
    // Check if we have the scale value
    if(options['scale'] != null) commandObject['scale'] = options['scale'];
  
    // Execute the command
    this.command(commandObject, options, callback);
  }
  
  /**
   * @ignore
   */
  var __executeQueryCommand = function(self, db_command, options, callback) {
    // Options unpacking
    var read = options['read'] != null ? options['read'] : false;
    var raw = options['raw'] != null ? options['raw'] : self.raw;
    var onAll = options['onAll'] != null ? options['onAll'] : false;
    var specifiedConnection = options['connection'] != null ? options['connection'] : null;
  
    // Correct read preference to default primary if set to false, null or primary
    if(!(typeof read == 'object') && read._type == 'ReadPreference') {
      read = (read == null || read == 'primary' || read == false) ? ReadPreference.PRIMARY : read;
      if(!ReadPreference.isValid(read)) return callback(new Error("Illegal readPreference mode specified, " + read));
    } else if(typeof read == 'object' && read._type == 'ReadPreference') {
      if(!read.isValid()) return callback(new Error("Illegal readPreference mode specified, " + read.mode));
    }
  
    // If we have a read preference set and we are a mongos pass the read preference on to the mongos instance,
    if(self.serverConfig.isMongos() && read != null && read != false) {
      db_command.setMongosReadPreference(read);
    }
  
    // If we got a callback object
    if(typeof callback === 'function' && !onAll) {
      // Override connection if we passed in a specific connection
      var connection = specifiedConnection != null ? specifiedConnection : null;
  
      if(connection instanceof Error) return callback(connection, null);
  
      // Fetch either a reader or writer dependent on the specified read option if no connection
      // was passed in
      if(connection == null) {
        connection = read == null || read == 'primary' || read == false ? self.serverConfig.checkoutWriter(true) : self.serverConfig.checkoutReader(read);
      }
  
      // Ensure we have a valid connection
      if(connection == null) {
        return callback(new Error("no open connections"));
      } else if(connection instanceof Error || connection['message'] != null) {
        return callback(connection);
      }
  
      // Exhaust Option
      var exhaust = options.exhaust || false;
      // Register the handler in the data structure
      self.serverConfig._registerHandler(db_command, raw, connection, exhaust, callback);
      // Write the message out and handle any errors if there are any
      connection.write(db_command, function(err) {
        if(err != null) {
          // Call the handler with an error
          self.serverConfig._callHandler(db_command.getRequestId(), null, err);
        }
      });
    } else if(typeof callback === 'function' && onAll) {
      var connections = self.serverConfig.allRawConnections();
      var numberOfEntries = connections.length;
      // Go through all the connections
      for(var i = 0; i < connections.length; i++) {
        // Fetch a connection
        var connection = connections[i];
  
        // Ensure we have a valid connection
        if(connection == null) {
          return callback(new Error("no open connections"));
        } else if(connection instanceof Error) {
          return callback(connection);
        }
  
        // Register the handler in the data structure
        self.serverConfig._registerHandler(db_command, raw, connection, callback);
        // Write the message out
        connection.write(db_command, function(err) {
          // Adjust the number of entries we need to process
          numberOfEntries = numberOfEntries - 1;
          // Remove listener
          if(err != null) {
            // Clean up listener and return error
            self.serverConfig._removeHandler(db_command.getRequestId());
          }
  
          // No more entries to process callback with the error
          if(numberOfEntries <= 0) {
            callback(err);
          }
        });
  
        // Update the db_command request id
        db_command.updateRequestId();
      }
    } else {
      // Fetch either a reader or writer dependent on the specified read option
      var connection = read == null || read == 'primary' || read == false ? self.serverConfig.checkoutWriter(true) : self.serverConfig.checkoutReader(read);
      // Override connection if needed
      connection = specifiedConnection != null ? specifiedConnection : connection;
      // Ensure we have a valid connection
      if(connection == null || connection instanceof Error || connection['message'] != null) return null;
      // Write the message out
      connection.write(db_command, function(err) {
        if(err != null) {
          // Emit the error
          self.emit("error", err);
        }
      });
    }
  }
  
  /**
   * @ignore
   */
  var __retryCommandOnFailure = function(self, retryInMilliseconds, numberOfTimes, command, db_command, options, callback) {
    if(this._state == 'connected' || this._state == 'disconnected') this._state = 'connecting';
    // Number of retries done
    var numberOfRetriesDone = numberOfTimes;
    // Retry function, execute once
    var retryFunction = function(_self, _numberOfRetriesDone, _retryInMilliseconds, _numberOfTimes, _command, _db_command, _options, _callback) {
      _self.serverConfig.connect(_self, {}, function(err, result, _serverConfig) {
        if(_options) delete _options['connection'];
  
        // Adjust the number of retries left
        _numberOfRetriesDone = _numberOfRetriesDone - 1;
        // Definitively restart
        if(err != null && _numberOfRetriesDone > 0) {
          _self._state = 'connecting';
          // Close the server config
          _serverConfig.close(function(err) {
            // Retry the connect
            setTimeout(function() {
              retryFunction(_self, _numberOfRetriesDone, _retryInMilliseconds, _numberOfTimes, _command, _db_command, _options, _callback);
            }, _retryInMilliseconds);
          });
        } else if(err != null && _numberOfRetriesDone <= 0) {
          _self._state = 'disconnected';
          // Force close the current connections
          _serverConfig.close(function(_err) {
            // Force close the current connections
            if(typeof _callback == 'function') _callback(err, null);
          });
        } else if(err == null && _self.serverConfig.isConnected() == true && Array.isArray(_self.auths) && _self.auths.length > 0) {
          _self._state = 'connected';
          // Get number of auths we need to execute
          var numberOfAuths = _self.auths.length;
          // Apply all auths
          for(var i = 0; i < _self.auths.length; i++) {
            _self.authenticate(_self.auths[i].username, _self.auths[i].password, {'authdb':_self.auths[i].authdb}, function(err, authenticated) {
              numberOfAuths = numberOfAuths - 1;
  
              // If we have no more authentications to replay
              if(numberOfAuths == 0) {
                if(err != null || !authenticated) {
                  if(typeof _callback == 'function') _callback(err, null);
                  return;
                } else {
                  // Execute command
                  command(_self, _db_command, _options, _callback);
                  // Execute all the commands
                  if(_self.commands.length > 0) _execute_queued_command(_self);
                }
              }
            });
          }
        } else if(err == null && _self.serverConfig.isConnected() == true) {
          _self._state = 'connected';
  
          // Execute command
          command(_self, _db_command, _options, _callback);        
    
          processor(function() {
            // Execute any backed up commands
            while(_self.commands.length > 0) {
              // Fetch the command
              var command = _self.commands.shift();
              // Execute based on type
              if(command['type'] == 'query') {
                __executeQueryCommand(_self, command['db_command'], command['options'], command['callback']);
              } else if(command['type'] == 'insert') {
                __executeInsertCommand(_self, command['db_command'], command['options'], command['callback']);
              }
            }
          });
        } else {
          _self._state = 'connecting';
          // Force close the current connections
          _serverConfig.close(function(err) {
          // _self.serverConfig.close(function(err) {
            // Retry the connect
            setTimeout(function() {
              retryFunction(_self, _numberOfRetriesDone, _retryInMilliseconds, _numberOfTimes, _command, _db_command, _options, _callback);
            }, _retryInMilliseconds);
          });
        }
      });
    };
  
    // Execute function first time
    retryFunction(self, numberOfRetriesDone, retryInMilliseconds, numberOfTimes, command, db_command, options, callback);
  }
  
  /**
   * Execute db query command (not safe)
   * @ignore
   * @api private
   */
  Db.prototype._executeQueryCommand = function(db_command, options, callback) {
    var self = this;
  
    // Unpack the parameters
    if (typeof callback === 'undefined') {
      callback = options;
      options = {};
    }
  
    // fast fail option used for HA, no retry
    var failFast = options['failFast'] != null
      ? options['failFast']
      : false;
  
    // Check if the user force closed the command
    if(this._applicationClosed) {
      var err = new Error("db closed by application");
      if('function' == typeof callback) {
        return callback(err, null);
      } else {
        throw err;
      }
    }
  
    var config = this.serverConfig;
    // If the pool is not connected, attemp to reconnect to send the message
    if(this._state == 'connecting' && config.autoReconnect && !failFast) {
      return processor(function() {
        self.commands.push({
          type: 'query',
          db_command: db_command,
          options: options,
          callback: callback
        });
      })
    }
  
    if(!failFast && !config.isConnected(options.read) && config.autoReconnect 
        && (options.read == null 
          || options.read == false
          || options.read == ReadPreference.PRIMARY 
          || config.checkoutReader(options.read) == null)) {
      this._state = 'connecting';
      return __retryCommandOnFailure(this,
                                     this.retryMiliSeconds,
                                     this.numberOfRetries,
                                     __executeQueryCommand,
                                     db_command,
                                     options,
                                     callback);
    }
  
    if(!config.isConnected(options.read) && !config.autoReconnect && callback) {
      // Fire an error to the callback if we are not connected
      // and don't reconnect.
      return callback(new Error("no open connections"), null);
    }
  
    __executeQueryCommand(self, db_command, options, function (err, result, conn) {
      if(callback) callback(err, result, conn);
    });
  
  };
  
  /**
   * @ignore
   */
  var __executeInsertCommand = function(self, db_command, options, callback) {
    // Always checkout a writer for this kind of operations
    var connection = self.serverConfig.checkoutWriter();
    // Get safe mode
    var safe = options['safe'] != null ? options['safe'] : false;
    var raw = options['raw'] != null ? options['raw'] : self.raw;
    var specifiedConnection = options['connection'] != null ? options['connection'] : null;
    // Override connection if needed
    connection = specifiedConnection != null ? specifiedConnection : connection;
  
    // Ensure we have a valid connection
    if(typeof callback === 'function') {
      // Ensure we have a valid connection
      if(connection == null) {
        return callback(new Error("no open connections"));
      } else if(connection instanceof Error) {
        return callback(connection);
      }
  
      var errorOptions = _getWriteConcern(self, options, callback);
      if(errorOptions.w > 0 || errorOptions.w == 'majority' || errorOptions.j || errorOptions.journal || errorOptions.fsync) {      
        // db command is now an array of commands (original command + lastError)
        db_command = [db_command, DbCommand.createGetLastErrorCommand(safe, self)];
        // Register the handler in the data structure
        self.serverConfig._registerHandler(db_command[1], raw, connection, callback);      
      }
    }
  
    // If we have no callback and there is no connection
    if(connection == null) return null;
    if(connection instanceof Error && typeof callback == 'function') return callback(connection, null);
    if(connection instanceof Error) return null;
    if(connection == null && typeof callback == 'function') return callback(new Error("no primary server found"), null);
  
    // Write the message out
    connection.write(db_command, function(err) {
      // Return the callback if it's not a safe operation and the callback is defined
      if(typeof callback === 'function' && (safe == null || safe == false)) {
        // Perform the callback
        callback(err, null);
      } else if(typeof callback === 'function') {
        // Call the handler with an error
        self.serverConfig._callHandler(db_command[1].getRequestId(), null, err);
      } else if(typeof callback == 'function' && safe && safe.w == -1) {
        // Call the handler with no error
        self.serverConfig._callHandler(db_command[1].getRequestId(), null, null);
      } else if(!safe || safe.w == -1) {
        self.emit("error", err);
      }
    });
  }
  
  /**
   * Execute an insert Command
   * @ignore
   * @api private
   */
  Db.prototype._executeInsertCommand = function(db_command, options, callback) {
    var self = this;
  
    // Unpack the parameters
    if(callback == null && typeof options === 'function') {
      callback = options;
      options = {};
    }
  
    // Ensure options are not null
    options = options == null ? {} : options;
  
    // Check if the user force closed the command
    if(this._applicationClosed) {
      if(typeof callback == 'function') {
        return callback(new Error("db closed by application"), null);
      } else {
        throw new Error("db closed by application");
      }
    }
  
    // If the pool is not connected, attemp to reconnect to send the message
    if(self._state == 'connecting' && this.serverConfig.autoReconnect) {
      processor(function() {
        self.commands.push({type:'insert', 'db_command':db_command, 'options':options, 'callback':callback});
      })
    } else if(!this.serverConfig.isConnected() && this.serverConfig.autoReconnect) {
      this._state = 'connecting';
      // Retry command
      __retryCommandOnFailure(this, this.retryMiliSeconds, this.numberOfRetries, __executeInsertCommand, db_command, options, callback);
    } else if(!this.serverConfig.isConnected() && !this.serverConfig.autoReconnect && callback) {
      // Fire an error to the callback if we are not connected and don't do reconnect
      if(callback) callback(new Error("no open connections"), null);
    } else {
      __executeInsertCommand(self, db_command, options, callback);
    }
  }
  
  /**
   * Update command is the same
   * @ignore
   * @api private
   */
  Db.prototype._executeUpdateCommand = Db.prototype._executeInsertCommand;
  /**
   * Remove command is the same
   * @ignore
   * @api private
   */
  Db.prototype._executeRemoveCommand = Db.prototype._executeInsertCommand;
  
  /**
   * Wrap a Mongo error document into an Error instance.
   * Deprecated. Use utils.toError instead.
   *
   * @ignore
   * @api private
   * @deprecated
   */
  Db.prototype.wrap = utils.toError;
  
  /**
   * Default URL
   *
   * @classconstant DEFAULT_URL
   **/
  Db.DEFAULT_URL = 'mongodb://localhost:27017/default';
  
  /**
   * Connect to MongoDB using a url as documented at
   *
   *  docs.mongodb.org/manual/reference/connection-string/
   *
   * Options
   *  - **uri_decode_auth** {Boolean, default:false} uri decode the user name and password for authentication
   *  - **db** {Object, default: null} a hash off options to set on the db object, see **Db constructor**
   *  - **server** {Object, default: null} a hash off options to set on the server objects, see **Server** constructor**
   *  - **replSet** {Object, default: null} a hash off options to set on the replSet object, see **ReplSet** constructor**
   *  - **mongos** {Object, default: null} a hash off options to set on the mongos object, see **Mongos** constructor**
   *
   * @param {String} url connection url for MongoDB.
   * @param {Object} [options] optional options for insert command
   * @param {Function} callback this will be called after executing this method. The first parameter will contain the Error object if an error occured, or null otherwise. While the second parameter will contain the db instance or null if an error occured.
   * @return {null}
   * @api public
   */
  Db.connect = function(url, options, callback) {
    var args = Array.prototype.slice.call(arguments, 1);
    callback = typeof args[args.length - 1] == 'function' ? args.pop() : null;
    options = args.length ? args.shift() : null;
    options = options || {};
    var serverOptions = options.server || {};
    var mongosOptions = options.mongos || {};
    var replSetServersOptions = options.replSet || options.replSetServers || {};
    var dbOptions = options.db || {};
  
    // If callback is null throw an exception
    if(callback == null) throw new Error("no callback function provided");
  
    // Parse the string
    var object = parse(url);
    // Merge in any options for db in options object
    if(dbOptions) {
      for(var name in dbOptions) object.db_options[name] = dbOptions[name];
    }
  
    // Merge in any options for server in options object
    if(serverOptions) {
      for(var name in serverOptions) object.server_options[name] = serverOptions[name];
    }
  
    // Merge in any replicaset server options
    if(replSetServersOptions) {
      for(var name in replSetServersOptions) object.rs_options[name] = replSetServersOptions[name];    
    }
  
    // Merge in any replicaset server options
    if(mongosOptions) {
      for(var name in mongosOptions) object.mongos_options[name] = mongosOptions[name];    
    }
  
    // We need to ensure that the list of servers are only either direct members or mongos
    // they cannot be a mix of monogs and mongod's
    var totalNumberOfServers = object.servers.length;
    var totalNumberOfMongosServers = 0;
    var totalNumberOfMongodServers = 0;
    var serverConfig = null;
    var errorServers = {};
  
    // Failure modes
    if(object.servers.length == 0) throw new Error("connection string must contain at least one seed host");
  
    // If we have no db setting for the native parser try to set the c++ one first
    object.db_options.native_parser = _setNativeParser(object.db_options);
    // If no auto_reconnect is set, set it to true as default for single servers
    if(typeof object.server_options.auto_reconnect != 'boolean') {
      object.server_options.auto_reconnect = true;
    }
  
    // If we have more than a server, it could be replicaset or mongos list
    // need to verify that it's one or the other and fail if it's a mix
    // Connect to all servers and run ismaster
    for(var i = 0; i < object.servers.length; i++) {
      // Set up socket options
      var _server_options = {poolSize:1, socketOptions:{connectTimeoutMS:1000}, auto_reconnect:false};
  
      // Ensure we have ssl setup for the servers
      if(object.rs_options.ssl) {
        _server_options.ssl = object.rs_options.ssl;
        _server_options.sslValidate = object.rs_options.sslValidate;
        _server_options.sslCA = object.rs_options.sslCA;
        _server_options.sslCert = object.rs_options.sslCert;
        _server_options.sslKey = object.rs_options.sslKey;
        _server_options.sslPass = object.rs_options.sslPass;
      } else if(object.server_options.ssl) {
        _server_options.ssl = object.server_options.ssl;
        _server_options.sslValidate = object.server_options.sslValidate;
        _server_options.sslCA = object.server_options.sslCA;
        _server_options.sslCert = object.server_options.sslCert;
        _server_options.sslKey = object.server_options.sslKey;
        _server_options.sslPass = object.server_options.sslPass;
      }
  
      // Set up the Server object
      var _server = object.servers[i].domain_socket 
          ? new Server(object.servers[i].domain_socket, _server_options)
          : new Server(object.servers[i].host, object.servers[i].port, _server_options);
  
      var connectFunction = function(__server) {      
        // Attempt connect
        new Db(object.dbName, __server, {safe:false, native_parser:false}).open(function(err, db) {
            // Update number of servers
            totalNumberOfServers = totalNumberOfServers - 1;          
            // If no error do the correct checks
            if(!err) {
              // Close the connection
              db.close(true);
              var isMasterDoc = db.serverConfig.isMasterDoc;
              // Check what type of server we have
              if(isMasterDoc.setName) totalNumberOfMongodServers++;
              if(isMasterDoc.msg && isMasterDoc.msg == "isdbgrid") totalNumberOfMongosServers++;
            } else {
              errorServers[__server.host + ":" + __server.port] = __server;
            }
  
            if(totalNumberOfServers == 0) {
              // If we have a mix of mongod and mongos, throw an error
              if(totalNumberOfMongosServers > 0 && totalNumberOfMongodServers > 0)
                return callback(new Error("cannot combine a list of replicaset seeds and mongos seeds"));
              
              if(totalNumberOfMongodServers == 0 && object.servers.length == 1) {
                var obj = object.servers[0];
                serverConfig = obj.domain_socket ? 
                    new Server(obj.domain_socket, object.server_options)
                  : new Server(obj.host, obj.port, object.server_options);            
              } else if(totalNumberOfMongodServers > 0 || totalNumberOfMongosServers > 0) {
                var finalServers = object.servers
                  .filter(function(serverObj) {
                    return errorServers[serverObj.host + ":" + serverObj.port] == null;
                  })
                  .map(function(serverObj) {
                      return new Server(serverObj.host, serverObj.port, object.server_options);
                  });
                // Clean out any error servers
                errorServers = {};
                // Set up the final configuration
                if(totalNumberOfMongodServers > 0) {
                  serverConfig = new ReplSet(finalServers, object.rs_options);                
                } else {
                  serverConfig = new Mongos(finalServers, object.mongos_options);                         
                }
              }
  
              if(serverConfig == null) return callback(new Error("Could not locate any valid servers in initial seed list"));
              // Set up all options etc and connect to the database
              _finishConnecting(serverConfig, object, options, callback)
            }
          });        
      }
  
      // Wrap the context of the call
      connectFunction(_server);    
    }    
  }
  
  var _setNativeParser = function(db_options) {
    if(typeof db_options.native_parser == 'boolean') return db_options.native_parser;
  
    try {
      require('bson').BSONNative.BSON;
      return true;
    } catch(err) {
      return false;
    }
  }
  
  var _finishConnecting = function(serverConfig, object, options, callback) {
    // Safe settings
    var safe = {};
    // Build the safe parameter if needed
    if(object.db_options.journal) safe.j = object.db_options.journal;
    if(object.db_options.w) safe.w = object.db_options.w;
    if(object.db_options.fsync) safe.fsync = object.db_options.fsync;
    if(object.db_options.wtimeoutMS) safe.wtimeout = object.db_options.wtimeoutMS;
  
    // If we have a read Preference set
    if(object.db_options.read_preference) {
      var readPreference = new ReadPreference(object.db_options.read_preference);
      // If we have the tags set up
      if(object.db_options.read_preference_tags)
        readPreference = new ReadPreference(object.db_options.read_preference, object.db_options.read_preference_tags);
      // Add the read preference
      object.db_options.readPreference = readPreference;
    }
  
    // No safe mode if no keys
    if(Object.keys(safe).length == 0) safe = false;
  
    // Add the safe object
    object.db_options.safe = safe;
  
    // Set up the db options
    var db = new Db(object.dbName, serverConfig, object.db_options);
  
    // Open the db
    db.open(function(err, db){
      if(err == null && object.auth){
        // What db to authenticate against
        var authentication_db = db;
        if(object.db_options && object.db_options.authSource) {
          authentication_db = db.db(object.db_options.authSource);
        }
  
        // Authenticate
        authentication_db.authenticate(object.auth.user, object.auth.password, function(err, success){
          if(success){
            callback(null, db);
          } else {
            if(db) db.close();
            callback(err ? err : new Error('Could not authenticate user ' + auth[0]), null);
          }
        });
      } else {
        callback(err, db);
      }
    });
  }
  
  /**
   * State of the db connection
   * @ignore
   */
  Object.defineProperty(Db.prototype, "state", { enumerable: true
    , get: function () {
        return this.serverConfig._serverState;
      }
  });
  
  /**
   * @ignore
   */
  var _hasWriteConcern = function(errorOptions) {
    return errorOptions == true
      || errorOptions.w > 0
      || errorOptions.w == 'majority'
      || errorOptions.j == true
      || errorOptions.journal == true
      || errorOptions.fsync == true
  }
  
  /**
   * @ignore
   */
  var _setWriteConcernHash = function(options) {
    var finalOptions = {};
    if(options.w != null) finalOptions.w = options.w;  
    if(options.journal == true) finalOptions.j = options.journal;
    if(options.j == true) finalOptions.j = options.j;
    if(options.fsync == true) finalOptions.fsync = options.fsync;
    if(options.wtimeout != null) finalOptions.wtimeout = options.wtimeout;  
    return finalOptions;
  }
  
  /**
   * @ignore
   */
  var _getWriteConcern = function(self, options, callback) {
    // Final options
    var finalOptions = {w:1};
    // Local options verification
    if(options.w != null || typeof options.j == 'boolean' || typeof options.journal == 'boolean' || typeof options.fsync == 'boolean') {
      finalOptions = _setWriteConcernHash(options);
    } else if(options.safe != null && typeof options.safe == 'object') {
      finalOptions = _setWriteConcernHash(options.safe);
    } else if(typeof options.safe == "boolean") {
      finalOptions = {w: (options.safe ? 1 : 0)};
    } else if(self.options.w != null || typeof self.options.j == 'boolean' || typeof self.options.journal == 'boolean' || typeof self.options.fsync == 'boolean') {
      finalOptions = _setWriteConcernHash(self.options);
    } else if(self.safe.w != null || typeof self.safe.j == 'boolean' || typeof self.safe.journal == 'boolean' || typeof self.safe.fsync == 'boolean') {
      finalOptions = _setWriteConcernHash(self.safe);
    } else if(typeof self.safe == "boolean") {
      finalOptions = {w: (self.safe ? 1 : 0)};
    }
  
    // Ensure we don't have an invalid combination of write concerns
    if(finalOptions.w < 1 
      && (finalOptions.journal == true || finalOptions.j == true || finalOptions.fsync == true)) throw new Error("No acknowlegement using w < 1 cannot be combined with journal:true or fsync:true");
  
    // Return the options
    return finalOptions;
  }
  
  /**
   * Legacy support
   *
   * @ignore
   * @api private
   */
  exports.connect = Db.connect;
  exports.Db = Db;
  
  /**
   * Remove all listeners to the db instance.
   * @ignore
   * @api private
   */
  Db.prototype.removeAllEventListeners = function() {
    this.removeAllListeners("close");
    this.removeAllListeners("error");
    this.removeAllListeners("timeout");
    this.removeAllListeners("parseError");
    this.removeAllListeners("poolReady");
    this.removeAllListeners("message");
  }
  