annoying message when use mongodb

Question

I am using this code in order to use mongodb:

var mongo = require("mongodb");
var BSON = mongo.BSONPure;

var server = new mongo.Server('localhost', 27017, {auto_reconnect: true, safe: true});
var db = new mongo.Db('dbname', server);

db.open(function(err, db) {
    if(!err) {
        console.log("Connected to 'dbname' database");
        db.collection("items", {safe:true}, function(err, collection) {
            console.log("Open database");
            if (err) {
                console.log("The 'items' collection doesn't exist. Creating it with sample data.");
                var items = [];
                for (var i = 0; i < 10; i++) {
                    items.push({
                        title: "title" + i,
                        site_name: "site_name" + i,
                        url: "url" + i,
                        type: "type" + i,
                        image: "image" + i
                    });
                }
                db.collection("items", function(err, collection) {
                    collection.insert(items, {safe:true}, function(err, result) {});
                });
            }
        });
    }
});

When I ran the application I get the message:

========================================================================================
=  Please ensure that you set the default write concern for the database by setting    =
=   one of the options                                                                 =
=                                                                                      =
=     w: (value of > -1 or the string 'majority'), where < 1 means                     =
=        no write acknowlegement                                                       =
=     journal: true/false, wait for flush to journal before acknowlegement             =
=     fsync: true/false, wait for flush to file system before acknowlegement           =
=                                                                                      =
=  For backward compatibility safe is still supported and                              =
=   allows values of [true | false | {j:true} | {w:n, wtimeout:n} | {fsync:true}]      =
=   the default value is false which means the driver receives does not                =
=   return the information of the success/error of the insert/update/remove            =
=                                                                                      =
=   ex: new Db(new Server('localhost', 27017), {safe:false})                           =
=                                                                                      =
=   http://www.mongodb.org/display/DOCS/getLastError+Command                           =
=                                                                                      =
=  The default of no acknowlegement will change in the very near future                =
=                                                                                      =
=  This message will disappear when the default safe is set on the driver Db           =
========================================================================================

What is this message and how can I fix it? Is there any better way to use mongodb?

Answer 1

MongoDB is helpfully instructing you to set default write concern (w) parameter in it's DB settings.

Changing this line should do the trick

   var db = new mongo.Db('dbname', server, {w:1});

This will be fine for development/hacking, but you should understand the ramifications of this option before going to production.

MongoDB Write Concern Reference