Mongo makes new connection on each page refresh - node.js

Question

When I load my page I want some products to be shown, so I make a GET request and it retrieves them from the database. However, when I refresh the page I notice the old connection remains. How to make sure the old connections close?
Here's my code:
const MongoClient = require('mongodb').MongoClient;
const connection = (closure) => {
return MongoClient.connect(config.connectionString, (err, client) => {
if (err) {
return winston.log('error', now() + err);
}
closure(client);
});
};
...
router.get('/products', (req, res) => {
connection((client) => {
client.db('dbname').collection('collectionname')
.find({})
.toArray()
.then((products) => {
response.data = products;
response.message = "Products retrieved successfully!"
res.json(response);
})
.catch((err) => {
winston.log('error', now() + err);
sendError(err, res);
});
});
});

Answer 1

Well, each time your /products route is called, you do create a new MongoClient instance. In that extent to limit the number of connection to your Database, you may either connect once, and save your MongoClient instance:
let client = undefined;
const connection = (closure) => {
// Return the client if any...
if(client) return closure(client);
return MongoClient.connect(config.connectionString, (err, c) => {
if (err) {
return winston.log('error', now() + err);
}
// Save the client.
client = c;
closure(client);
});
};
...or simply close the MongoClient connection you instantiated once you're done with it:
router.get('/products', (req, res) => {
connection((client) => {
client.db('dbname').collection('collectionname')
.find({})
.toArray()
.then((products) => {
response.data = products;
response.message = "Products retrieved successfully!"
// Close the MongoClient...
client.close();
res.json(response);
})
.catch((err) => {
winston.log('error', now() + err);
sendError(err, res);
// Close the MongoClient...
client.close();
});
});
});
I would advise you to go with the first solution: The MongoClient maintains a connection pool, so having multiple clients does not have any advantages. In addition, it allows you to check whether or not the DB is remotely available, before executing anything else as well (just connect to the DB on your app init(), and save the client instance, and you'll be done).