How to handle multiple asynchronous connections in Mongoose

Question

Have to improve on my current Express/Mongoose server, thinking I may need to use mongoose.createConnection over mongoose.connect, and perhaps maintaining an array of connections, and deleting the indexes as the connection dies - so I need some input from your collective minds.

The script is essentially built up like this:

// Constants
var MONGO_SERVER = "mongodb://user:pass@localhost/dbname";

// Connection Handlers
function checkConnection(cb) {
    if (mongoose.Connection.STATES.connected !== mongoose.connection.readyState) connectMongo(cb());
    else cb();
}
function connectMongo(cb) {
    db = mongoose.connect(MONGO_SERVER,function(err){if (err) throw err; else if (typeof cb==="function") cb();});
}

// Setup connection
mongoose = require('mongoose');
var db = {};
connectMongo();
Schema = mongoose.Schema;
ObjectId = Schema.ObjectId;

// Schemas...
var UsersSchema = new Schema({
    display_name    : String,
    email           : String
}); 
//...
var users = mongoose.model('Users',UsersSchema);

//...
function login(conn,obj,link_id) {
    checkConnection(function() {
        try {   
            //...
        }
        catch (ex) {
            console.log(ex.message);
        }
    });
}

Now, this works, but seeing some performance issues and some queries appear to be hanging tells me I need to re-shape this type of execution, and maybe making var db = {} to be an array, and using createConnection pushed to the end of it. Don't need a direct answer, just a nudge in the right direction.

Thanks.

Unless I'm missing some part of the question, doesn't mongoose's connection pool handle asynchronous connections automatically? See the connection docs. — Ash
– Ash, Commented Feb 14, 2016 at 14:41
As Ashley B said, Mongoose handle all these async thing. Still not satisfied, you can mongoose-and-multiple-database-in-single-node-js-project — xdeepakv
– xdeepakv, Commented Feb 14, 2016 at 14:58

Ash · Accepted Answer · 2016-02-14 17:21:00Z

3

Write-up from my comment:

Mongoose handles async connections by default using connection pools. You can specify the pool size like so:

var options = {
  server: { poolSize: 10 } // default is '5'
}

mongoose.connect('mongodb://username:password@host:port/database', options);

A connection will be used from the connection pool and then released back to the pool once the transaction has been completed.

answered Feb 14, 2016 at 17:21

Ash

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2 Comments

Jester Over a year ago

Cheers Ashley - that's pretty much what I needed to know! And the tips from that other page Deepak was very useful. With the changes made in the options object, working a lot more smoother now.

Ash Over a year ago

No problem, if you want to make it a bit cleaner (if you have no other options) you can also just add it to the mongo connection uri like so: mongodb://username:password@host:port/database?poolSize=4

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