success! (except for last one)

gistfile1.js

var mongodb         = require('mongodb')
  , Db              = mongodb.Db
  , Server          = mongodb.Server
  , ReplSetServers  = mongodb.ReplSetServers;

var mode = process.argv.slice(2)[0] || 'server';

var mongoConfig = {
    replset : {
        servers : [
            { host: 'localhost', port: 27017, options : { auto_reconnect: true, poolSize: 1 } }
          , { host: 'localhost', port: 27018, options : { auto_reconnect: true, poolSize: 1 } }
          , { host: 'localhost', port: 27019, options : { auto_reconnect: true, poolSize: 1 } }
        ]
      , options : {
            rs_name         : 'rs0'
          , read_secondary  : true
        }
    }
  , server : { host: 'localhost', port: 27017, options : { auto_reconnect: true } }
  , options : {
        safe  : { w: 'all', wtimeout: 5000 }
    }
  , db   : 'test-replset'
};

function createServer(serverInfo) {
    return new Server(serverInfo.host, serverInfo.port, serverInfo.options);
}

function createReplicaSet(replsetConfig) {
    return new ReplSetServers(replsetConfig.servers.map(createServer), replsetConfig.options);
}

function connect(callback) {
    var replset, server;

    if(mode == 'replset') {
        replset = createReplicaSet(mongoConfig.replset);
    } else {
        server = createServer(mongoConfig.server);
    }

    if(mongoConfig.options.safe && mongoConfig.options.safe.w == 'all' ) {
        mongoConfig.options.safe.w = (replset) ? replset.servers.length : 1;
    }
    
    var client = new Db( mongoConfig.db
                       , replset || server
                       , {safe:true } );
    client.open(function(err, db) {
        if(err) {
            console.log(err);
            return;
        }
        console.log(err || "Connected to MongoDB");
        callback(null, client);
    });
}

function success(doc) {
    console.log("success!", doc);
}

function error(err) {
    console.log("ERROR",err.message);
}

connect(function(err, db) {
    db.collection('files', function(err, files) {
        files.remove({}, function(err) {
            if(err) {
                error(err || new Error('Error emptying collection'));
                return;
            }
            function insertAndFind(i) {
                files.insert({servername: "hello"+i, originalname: "world"+i}, function(err, docs) {
                    if(err || !docs) {
                        error(err || new Error('Error inserting file'));
                        return;
                    }
                    files.findOne({servername: "hello"+i}, function(err, doc) {
                        if(err || !doc) {
                            error(err || new Error('File not found'));
                            return;
                        }
                        success(doc);
                    });
                });
                if(i-->0) {
                    process.nextTick(function() {
                        insertAndFind(i);
                    });
                }
            }
            insertAndFind(10);
        });
    });
});

output is :

Connected to MongoDB
success! { servername: 'hello9',
originalname: 'world9',
_id: 50aab8976fc9921727000002 }
success! { servername: 'hello8',
originalname: 'world8',
_id: 50aab8976fc9921727000003 }
success! { servername: 'hello7',
originalname: 'world7',
_id: 50aab8976fc9921727000004 }
success! { servername: 'hello6',
originalname: 'world6',
_id: 50aab8976fc9921727000005 }
success! { servername: 'hello3',
originalname: 'world3',
_id: 50aab8976fc9921727000008 }
success! { servername: 'hello4',
originalname: 'world4',
_id: 50aab8976fc9921727000007 }
success! { servername: 'hello5',
originalname: 'world5',
_id: 50aab8976fc9921727000006 }
success! { servername: 'hello0',
originalname: 'world0',
_id: 50aab8976fc992172700000b }
success! { servername: 'hello2',
originalname: 'world2',
_id: 50aab8976fc9921727000009 }
success! { servername: 'hello1',
originalname: 'world1',
_id: 50aab8976fc992172700000a }
ERROR File not found