How to test Connection Pooling in nodeJS using mogoDB Database?

Question

How to test Connection Pooling in NodeJS using MongoDB Database?

Answer 1

Instead of having our app wait around for a request before connecting to the database we're going to have it connect when the application starts, and we're going to give ourselves a pool of connections to draw from as and when we need them.

Here we're using the node-mongodb-native driver, which like most available MongoDB drivers has an option that you can use to set the size of your connection pool. For this driver, it's called poolSize, and has a default value of 5. We can make use of the poolsize option by creating a database connection variable in advance, and letting the driver allocate available spaces as new connection requests come in:

// This is a global variable we'll use for handing the MongoDB client
var mongodb;

// Connection URL
var url = '[connectionString]';

// Create the db connection
MongoClient.connect(url, function(err, db) {  
    assert.equal(null, err);
    mongodb=db;
    }
);

To change the size of the connection pool from the default, we can pass poolSize in as an option:

// Create the database connection
MongoClient.connect(url, {  
  poolSize: 10
  // other options can go here
},function(err, db) {
    assert.equal(null, err);
    mongodb=db;
    }
);

Now we have a connection ready and waiting. To use our new connection, we just need to make use of our new global variable, mongodb when a request is made:

// Use the connect method to connect to the server when the page is requested
app.get('/', function(request, response) {  
    mongodb.listCollections({}).toArray(function(err, collections) {
        assert.equal(null, err);
        collections.forEach(function(collection) {
            console.log(collection);
        });
    })
    response.send('See console for a list of available collections');
});