Question

I’m using nodejs and a mongoDB – and I’m having some connection issues.

Well, actually “wake” issues! It connects perfectly well – is super fast and I’m generally happy with the results.

My problem: If i don’t use the connection for a while (i say while, because the timeframe varies 5+ mins) it seems to stall. I don’t get disconnection events fired – it just hangs.

Eventually i get a response like Error: failed to connect to [ * .mongolab.com: * ] – ( * = masked values)

A quick restart of the app, and the connection’s great again. Sometimes, if i don’t restart the app, i can refresh and it reconnects happily.

This is why i think it is “wake” issues.

Rough outline of code:

I’ve not included the code – I don’t think it’s needed. It works (apart from the connection dropout)

Things to note: There is just the one “connect” – i never close it. I never reopen.

I’m using mongoose, socketio.

/* constants */

var mongoConnect = 'myworkingconnectionstring-includingDBname';


/* includes */

/* settings */

/* Schema */

var db = mongoose.connect(mongoConnect);

    /* Socketio */

io.configure(function (){
    io.set('authorization', function (handshakeData, callback) {

    });
});

io.sockets.on('connection', function (socket) {

});//sockets

io.sockets.on('disconnect', function(socket) {
    console.log('socket disconnection')
});

/* The Routing */

app.post('/login', function(req, res){  

});

app.get('/invited', function(req, res){

});

app.get('/', function(req, res){

});

app.get('/logout', function(req, res){

});

app.get('/error', function(req, res){

});

server.listen(port);
console.log('Listening on port '+port);

db.connection.on('error', function(err) {
    console.log("DB connection Error: "+err);
});
db.connection.on('open', function() {
    console.log("DB connected");
});
db.connection.on('close', function(str) {
    console.log("DB disconnected: "+str);
});

I have tried various configs here, like opening and closing all the time – I believe though, the general consensus is to do as i am with one open wrapping the lot. ??

I have tried a connection tester, that keeps checking the status of the connection… even though this appears to say everthing’s ok – the issue still happens.

I have had this issue from day one. I have always hosted the MongoDB with MongoLab.
The problem appears to be worse on localhost. But i still have the issue on Azure and now nodejit.su.

As it happens everywhere – it must be me, MongoDB, or mongolab.

Incidentally i have had a similar experience with the php driver too. (to confirm this is on nodejs though)

It would be great for some help – even if someone just says “this is normal”

thanks in advance

Rob

Answer 1

Thanks for all the help guys – I have managed to solve this issue on both localhost and deployed to a live server.

Here is my now working connect code:

var MONGO = {
    username: "username",
    password: "pa55W0rd!",
    server: '******.mongolab.com',
    port: '*****',
    db: 'dbname',
    connectionString: function(){
        return 'mongodb://'+this.username+':'+this.password+'@'+this.server+':'+this.port+'/'+this.db;
    },
    options: {
        server:{
            auto_reconnect: true,
            socketOptions:{
                connectTimeoutMS:3600000,
                keepAlive:3600000,
                socketTimeoutMS:3600000
            }
        }
    }
};

var db = mongoose.createConnection(MONGO.connectionString(), MONGO.options);

db.on('error', function(err) {
    console.log("DB connection Error: "+err);
});
db.on('open', function() {
    console.log("DB connected");
});
db.on('close', function(str) {
    console.log("DB disconnected: "+str);
});

I think the biggest change was to use “createConnection” over “connect” – I had used this before, but maybe the options help now. This article helped a lot http://journal.michaelahlers.org/2012/12/building-with-nodejs-persistence.html

If I’m honest I’m not overly sure on why I have added those options – as mentioned by @jareed, i also found some people having success with “MaxConnectionIdleTime” – but as far as i can see the javascript driver doesn’t have this option: this was my attempt at trying to replicate the behavior.

So far so good – hope this helps someone.

UPDATE: 18 April 2013 note, this is a second app with a different setup

Now I thought i had this solved but the problem rose it’s ugly head again on another app recently – with the same connection code. Confused!!!

However the set up was slightly different…

This new app was running on a windows box using IISNode. I didn’t see this as significant initially.

I read there were possibly some issues with mongo on Azure (@jareed), so I moved the DB to AWS – still the problem persisted.

So i started playing about with that options object again, reading up quite a lot on it. Came to this conclusion:

options: {
    server:{
        auto_reconnect: true,
        poolSize: 10,
        socketOptions:{
            keepAlive: 1
        }
    },
    db: {
        numberOfRetries: 10,
        retryMiliSeconds: 1000
    }
}

That was a bit more educated that my original options object i state.
However – it’s still no good.

Now, for some reason i had to get off that windows box (something to do with a module not compiling on it) – it was easier to move than spend another week trying to get it to work.

So i moved my app to nodejitsu. Low and behold my connection stayed alive! Woo!

So…. what does this mean… I have no idea! What i do know is is those options seem to work on Nodejitsu…. for me.

I believe IISNode uses some kind of “forever” script for keeping the app alive. Now to be fair the app doesn’t crash for this to kick in, but i think there must be some kind of “app cycle” that is refreshed constantly – this is how it can do continuous deployment (ftp code up, no need to restart app) – maybe this is a factor; but i’m just guessing now.

Of course all this means now, is this isn’t solved. It’s still not solved. It’s just solved for me in my setup.