Write and read in Mongo collection with asynchronous node.js implementation - node.js

Question

I'm beginner in nodeJS and I have some problems to manage asynchronous way of thinking.
I try to save data in my MongoDB Database and retrieve it. I get my data from a websocket service each 1 ms to 5 sec.
When it's each 5 sec there is no problem but each 1ms, when I display my collection content, the data are not already saved.
Here is my code :
// --Websocket event coming every 1 ms--//
while (1) { //Simulate Websocket events coming every 1 ms
dataBookSave(dataArrayfunction, function(log) { //array of data received from websocket event
console.log(log); //Display the callback log from the function dataBookSave
var query = ""; // Empty query in MongoDB to retrieve all data
mongoDb.find(dbName, collectionName, query, function(result) { // get all data from the MongoDB collection.
console.log(results); //Display all data from my MongoDB collection
});
}
}
function dataBookSave(dataArray, callback) {
if (dataArray.length < 1) callback("dataBookSave1"); //test if the array is empty. if yes, generate the callback
for (var i = 0; i < dataArray.length; i++) {
(function(i) { //closure the for loop
var objAdd = JSON.parse('{"data" : ' + dataArray[i] + ' }'); // create the object to add in the collection
mongoDb.insertCollection(dbName, collectionName, objAdd, function() { // insert function in MongoDB
if (i == dataArray.length - 1) // test if the loop is finished.
{
callback("dataBookSave2"); // if yes, generate the callback
}
});
})(i);
}
}
function insertCollection(dbName, collectionName, myObj, callback) {
var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://localhost:27017/" + dbName;
MongoClient.connect(url, function(err, db) {
if (err) throw err;
var dbase = db.db(dbName);
dbase.collection(collectionName).insertOne(myObj, function(err, res) {
if (err) throw err;
db.close();
callback();
});
});
}
function find(dbName, collectionName, query, callback) {
var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://localhost:27017/" + dbName;
MongoClient.connect(url, function(err, db) {
if (err) throw err;
var dbase = db.db(dbName);
dbase.collection(collectionName).find(query).sort({
_id: -1
}).toArray(function(err, result) {
if (err) throw err;
callback(result);
db.close();
});
});
}
I see when the for loop is executed, the asynchronous process iterate each data of the table and don't wait the insert database function to be executed. When the for loop is done, I read the collection in MongoDB. The problem is that data is still in queue, going to be written in the collection.
How can I resolve that? Give up with the async concept? Use closure? Find a best callback implementation?

Answer 1

You definitely don't want to connect/close the connection to your db every 1ms. Keeping the connection open is in this case recommended.
I haven't run the code bellow but it should work
var MongoClient = require('mongodb').MongoClient;
var url = "mongodb://localhost:27017/" + dbName;
var mongodb;
var collectionName = "some-collection";
MongoClient.connect(url, function(err, db) {
if (err) throw err;
mongodb = db;
run();
});
function run() {
// --Websocket event coming every 1 ms--//
while (1) { //Simulate Websocket events coming every 1 ms
dataBookSave(dataArrayfunction, function(log) { //array of data received from websocket event
console.log(log); //Display the callback log from the function dataBookSave
find(collectionName, function(result) { // get all datas from the MongoDB collection.
console.log(results); //Display all datas from my MongoDB collection
});
});
}
}
function dataBookSave(dataArray, callback) {
if (dataArray.length < 1) callback("dataBookSave1");
var arr = [];
// push object to arr for bulk insertion
for (var i = 0; i < dataArray.length; i++) {
arr.push({
data: dataArray[i]
});
}
insert(collectionName, arr, function() {
callback("dataBookSave2");
});
}
function insert(col, arr, callback) {
mongodb
.collection(col)
.insertMany(arr, function(err, res) {
if (err) throw err;
callback();
});
}
function find(collectionName, query, callback) {
mongodb
.collection(collectionName)
.find(query)
.sort({ _id: -1 })
.toArray(function(err, result) {
if (err) throw err;
callback(result);
});
}