Saving node.js stream to mongodb - how to properly connect?

The script I am working with is here: https://gist.github.com/2759751

I want to modify some code to store a streaming, parsed message from a node.js app to a mongodb collection for later access. So far I am working with tutorial code and am confused about getting the db.open() mechanism just right, if I use db.open(), and since it's a stream, it complains that it can't open it multiple times. If I remove it, it says it can't find an open connection. How do I open the connection one time to allow storing of the stream?

I instantiate mongo with:

mongo = require('mongodb'),
    db = new mongo.Db('wikis', new mongo.Server('localhost', 27017, {}), {});

the stream kicks out an object like this:

return {
    flag: flag,
    page: page,
    pageUrl: pageUrl,
    url: m[3],
    delta: delta,
    comment: m[6],
    wikipedia: wikipedia,
    wikipediaUrl: wikipediaUrl,
    wikipediaShort: config.wikipedias[msg[0]].short,
    wikipediaLong: config.wikipedias[msg[0]].long,
    user: user,
    userUrl: userUrl,
    unpatrolled: isUnpatrolled,
    anonymous: anonymous,
    robot: isRobot,
    namespace: namespace,
    minor: isMinor

}

And I want to store parts of the stream like this:

function saveRecs(msg){
//db.open(function(){

    db.collection('wikiCollection', function(err, collection){
        doc = {
            "page": msg.page,
            "url": msg.url,
            "user": msg.user
        };

        collection.insert(doc, function(){
            console.log('Got a record, boss!');
        }); 
    });
//});
}