MongoDB not closing connections from NodeJS app - node.js

Question

I have a node application that makes a call to mongoDB every 10 seconds, but looking at the output in my terminal, the connections just keep counting up and never seem to close:
My code to hit the ddb every 10 seconds:
const MongoClient = require("mongodb").MongoClient
setInterval(function(){
MongoClient.connect(uri, (err, client) => {
if (err){
console.log(err);
}
database = client.db(databaseName)
getData(function(data){
if(data.length > 0){
db_response = data;
params["fieldA"] = db_response[0]['fieldA'];
}
})
})
}, 10000)
function getData(callback){
var query = { fieldA: "foo" };
database.collection(CollectionName).find(query).toArray(function(err, result){
if (err){
throw err;
}
callback(result);
})
}
(The vars uri, CollectionName and databaseName are declared earlier) I guess what i need to do (and havent yet figured out) is to connect to the DB once when the server starts, and then run the getData() function on successful connection, does that mean the database variable needs to be a global var??

Answer 1

As you correctly identified you only need to create your db connection once. So rather than wrapping the the db connection creation with setInterval, wrap setInterval around the only function you want to repeat, in this case getData.
On your other question, the database variable doesn't need to global but you are right getData does need to use it. Therefore pass it as an argument along with your callback function.
If you want to close your connection use client.close(); inside MongoClient.connect
const MongoClient = require("mongodb").MongoClient
MongoClient.connect(uri, (err, client) => {
if (err){
console.log(err);
}
const database = client.db(databaseName);
setInterval(function(){
getData(database, function(data){
if(data.length > 0){
db_response = data;
params["fieldA"] = db_response[0]['fieldA'];
}
})
}, 10000)
})
function getData(db, callback){
var query = { fieldA: "foo" };
db.collection(CollectionName).find(query).toArray(function(err, result){
if (err){
throw err;
}
callback(result);
})
}