Mongoose and the autoReconnect option conundrum

Question

I'm really confused with mongoose autoReconnect option inside mongoose.connect methods. My problem is that my server may start before database connection is ready, so I have to handle this at the start of my server code. Well, let me explain what I have until now:

First, I tried the documented way:

const db = mongoose.connection;
db.once('open', () => console.log('database connected'));
mongoose.connect(dbUri, { autoReconnect: true });

It kinda works, (mongo console shows: I NETWORK [listener] connection accepted from 127.0.0.1:52896 #1 (1 connection now open)) but it never calls the open callback. What is really weird about this solution though is that db.readyState never become 1 (which I suppose it's the reason the callback is never called).

After that, I searched for a solution and found several of them, including those here, and on github. To sum up them, here it is the basic solution:

function connect() {
    mongoose.connect(dbUri, { autoReconnect: true });
}

const db = mongoose.connection;

db.once('open', () => console.log('database connected'));

db.on('error', () => {
    console.log('database connection error');
    mongoose.disconnect();
});

db.on('disconnected', () => {
    console.log('database disconnected.');
    connect();
});

connect();

Again, this solution kida works too, but this time, every call to connect() method creates a new connection, so my mongo console show something like:

I NETWORK  [listener] connection accepted from 127.0.0.1:52896 #5 (35 connections now open)
I NETWORK  [listener] connection accepted from 127.0.0.1:52896 #6 (36 connections now open)
I NETWORK  [listener] connection accepted from 127.0.0.1:52896 #7 (37 connections now open)
...

Playing around I find out that's because of the autoReconnect option. If i set it to false (which is really not recommended by the documentation), a single connection is made when database is ready. But I think that autoReconnect means to do it not just when the connection is made, but while it's active through the execution of the application.

So, what am I missing here? Is there something that I should be doing in the first example? Do I keep autoReconnect and ignore the multiple connection thing? Or there is another solution I didn't find?

Node: 8.9.0
MongoDB: 3.6.5
Mongoose: 5.0.11

Mongoose and the autoReconnect option conundrum

0 Answers0