What is the best way to open a persistent (mongo) database connection in NodeJS

Question

I am using the node-mongodb-native drivers and I am looking for a way to open a persistent database connection rather than opening/closing it each time.

A simplified connection might look like this...

var DB = new mongo.Db('vows', new mongo.Server("127.0.0.1", 27017, {})),
    connection = DB.open(function(err, db) {
       // Here we have access to db
    });

How can I make the db object accessible to any module in my application? Rather than having to open the connection for every module separately?

Can this be done using module.exports? Or a global variable?

Peter O. · Accepted Answer · 2012-03-12 16:27:17Z

5

My solution:

getClient = function(cb) {
    if(typeof client !== "undefined") {
        return cb(null, client);
    } else {
        db.open(function(err, cli) {
            client = cli;
            getClient(cb);
        });
    }
}

Now, instead of

db.open(function(err, client) {
    ...stuff...
});

Do:

getClient(function(err, client) {
    ...stuff...
});

Your first db call opens a connection, the others use that connection.

BTW: suggestions on checking that client is still alive?

edited Mar 12, 2012 at 16:27

Peter O.

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answered Mar 12, 2012 at 16:06

joe

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1 Comment

Bin Wang Over a year ago

The way to see the client is still alive is setTimeout(...) after call getClient, and in the mongo shell, use db.runCommand({serverStatus: 1}).connections to see how many connections there are. I don't think the client will still alive.

Raynos · Accepted Answer · 2013-03-11 16:27:54Z

1

Edit: Don't use mongoose, Use something like mongo-col or mongo-client. Then have a single client open in your application. I have ./client.js file that exports a properly opened and configured mongo client.

Mongoose is a solid abstraction on top of mongodb that will allow you to handle mongodb more easily. It's a worth a look.

What you really want to do though is re-open your client every time you do anything with mongo.

You don't keep an open connection to any other database.

Just place your DB in a module along with some helper / wrapper functions.

edited Mar 11, 2013 at 16:27

answered May 25, 2011 at 18:34

Raynos

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3 Comments

Bin Wang Over a year ago

Isn't it too expensive to reopen the client every time?

Raynos Over a year ago

@BinWang I am wrong about every thing. You shouldn't use mongoose, it sucks. And you shouldnt reopen the client every time.

Bin Wang Over a year ago

I'm using generic-pool now. It also opens many clients (connect to mongodb with "poolSize=1" many times) at one time, keep it open and manage the pool itself. Does this affect the benchmark?

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