Develop Reference

Release PostgeSQL connection Pool in Nodejs

I am trying to connect my application to the database using the connection pool method, its connecting fine, and data insertion is happening fine without any issues but other queries in the same file are slowing down.
I have tried with release() method also not working properly.
How can release the pool to the next query once it's executed the current query?
Below is my dbpool.js file code where I am writing a common generalized database connection,
var pg = require('pg');
var PGUSER = 'postgres';
var PGDATABASE = 'test_database';
var config = {
user: PGUSER, // name of the user account
host: 'localhost',
database: PGDATABASE, // name of the database
password: 'password#AWS',
port: 5432,
max: 10,
idleTimeoutMillis: 10000
};
const pool = new pg.Pool(config);
const DB = {
query: function(query, callback) {
pool.connect((err, client, done) => {
if(err){ return callback(err); }
client.query(query, (err, results) => {
// done();
client.release();
// if(err) { console.error("ERROR: ", err) }
if(err) { return callback(err); }
callback(null, results.rows);
})
});
}
};
module.exports = DB;
I tried with both the done() and client.release() method but no luck. If I use both then I am getting an error message client is already released.
Below is my socket.js file code:
var express = require('express');
const connection = require('./dbpool.js');
if(arData == '0022'){
const queryText = "INSERT INTO alert(alert_data) VALUES('"+arData+"')";
connection.query(queryText,(err, res) => {
if(err){
console.log(err.stack);
}
});
}
if(arData == '0011'){
const queryText = "INSERT INTO table2(alert_data) VALUES('"+arData+"')";
connection.query(queryText,(err, res) => {
if(err){
console.log(err.stack);
}
});
}
function ReverseCommunication(){
const select1 = "SELECT * FROM alert WHERE action = '0' ORDER BY alert_id ASC LIMIT 1";
connection.query(select1, (err, res) =>{
if(err) {
console.log("Error1");
res.json({"error":true});
}
else{
console.log("res==",res);
}
});
}
setInterval(function(){
ReverseCommunication();
}, 2000)

With pool you shouldn't need to close the connection. With pool it will reuse the connection pool for subsequent request so you don't have to connect to the DB each time.
(i'm not a PG expert here, sure other could expand on that way better then I )
What works for us is to set up the dbpool file you have like this
const {Pool,Client} = require('pg');
const pool = new Pool({
user: process.env.POSTGRES_USER,
host: process.env.POSTGRES_URL,
database: process.env.POSTGRES_DATABASE,
password: process.env.POSTGRES_PASSWORD,
port: process.env.POSTGRES_PORT,
keepAlive: true,
connectionTimeoutMillis: 10000, // 10 seconds
max: 10
});
pool.connect()
.then(() => console.log('pg connected'))
.catch(err => console.error(err))
module.exports = pool
Then use the pool.query like you have now with pool.connect
Also, just a side note what lib are you using for PG? Noticed your queries are dynamic, you may want to adjust those to prevent possible SQL-injection.

MongoDB get data to display in HTML

I'm trying to display mongodb data in my html page. I've already managed to insert data in db but for some reason my "get" function does not work.
I'm using node.js with express framework and Angular for front-end and routing.
This is my "get" function to retreive data from MongoDB:
var mongo = require('mongodb');
var assert = require('assert');
var url = 'mongodb://localhost:27017/loodgieters';
router.get('/get-data', function(req, res, next) {
var resultArray = [];
mongo.connect(url, function(err, db){
assert.equal(null, err);
var cursor = db.collection('user-data').find();
cursor.forEach(function(doc, err){
assert.equal(null, err);
resultArray.push(doc);
}, function(){
db.close();
res.render('index', {items: resultArray});
});
});
});
And my "post" which works
router.post('/insert', function(req, res, next) {
var item = {
name: req.body.name,
adress: req.body.adress,
postal: req.body.postal,
city: req.body.city,
email: req.body.email,
phone: req.body.phone,
quotation: req.body.quotation,
message: req.body.message
};
mongo.connect(url, function(err, db) {
assert.equal(null, err);
db.collection('user-data').insertOne(item, function(err, result){
assert.equal(null, err);
console.log('Item inserted');
db.close();
});
});
res.redirect('/contact');
});

i am not sure if this is the correct way to open and close mongo connection each time you are trying to query .
if you want to go for another approach then use mongoose
and follow something like this
https://pastebin.com/g7aatzzj

I think that you have a mistake in your .find().forEach function callbacks. The error handling seems to be in the endCallback not the iteratorCallback.
According to the official doc, the correct way should be :
var mongo = require('mongodb');
var assert = require('assert');
var url = 'mongodb://localhost:27017/loodgieters';
router.get('/get-data', function(req, res, next) {
var resultArray = [];
mongo.connect(url, function(err, db){
assert.equal(null, err);
var cursor = db.collection('user-data').find({});
cursor.forEach(function(doc){
assert.notEqual(null, doc);
resultArray.push(doc);
}, function(err, doc){
assert.equal(null, err);
db.close();
res.render('index', {items: resultArray});
});
});
});
This can also be found in their unit tests
var cursor = collection.find({})
.map(function(x) { return {a:1}; })
.batchSize(5)
.limit(10);
cursor.forEach(function(doc) {
test.equal(1, doc.a);
}, function(err, doc) {
test.equal(null, err);
db.close();
test.done();
});
I think that you must have a error that is not passed to the first callback and not handled in the second one. So you do not see the error.

Try to insert an empty object to the find() function as following:
var cursor = db.collection('user-data').find({});

I have just run your code and modified it a bit for my purposes.
Please find the following snippet
//Instantiate MongoClient
var mongo = require('mongodb').MongoClient;
//Assert library (Perhaps overkill if you are writing production-level code)
var assert = require('assert');
//Express engine
var express = require('express');
//URL for my mongo instance
//Connecting to the blog database
var url = 'mongodb://localhost:27017/blog';
//Instantiate express
var router = express();
//Get operation
router.get('/get', function(req, res, next) {
var resultArray = [];
mongo.connect(url, function(err, db){
assert.equal(null, err);
var cursor = db.collection('posts').find();
cursor.forEach(function(doc, err){
assert.equal(null, err);
resultArray.push(doc);
}, function(){
db.close();
//I have no index file to render, so I print the result to console
//Also send back the JSON string bare through the channel
console.log(resultArray);
res.send(resultArray);
});
});
});
//Start listeninig
//Hardcoded port 1000
var server = router.listen(1000, function() {
var host = server.address().address;
var port = server.address().port;
console.log("Content Provider Service listening at http://%s:%s", host, port);
});
Therefore to get this working for you:
Change the url to 'mongodb://localhost:27017/loodgieters';
Change router to '/get-data'
I hope this helps!
Also consider using splitting the implementation of the get operation to another module to help for the Separation of Responsibilities to make your code more robust.

node js express - querying the price field

Im having trouble figuring out how to query the price. My current attempt is not working and im not sure what you have to type in the local host.
http://localhost:3000/priceSearch?
I have implemented - orderSearch.find({price:{$gt:400, $lt: 700}})
the price field in my mongodb is a number not a a string
Thank you:D
Here is my code:
priceSearch.ejs
var express = require('express');
var router = express.Router();
var mongodb = require('mongodb');
var MongoClient = mongodb.MongoClient;
var url = 'mongodb://localhost:27017/WishList';
router.get('/', function (req, res) {
var price = req.query.price;
MongoClient.connect(url, function (err, db) {
if (err) {
console.log("Unable to connect to the server", err);
} else {
console.log("Connection established...");
var orderSearch = db.collection('orders');
// find document who satisify price
orderSearch.find({price:{$gt:400, $lt: 700}}).toArray(function (err, result) {
if (err) {
res.send(err);
} else if (result.length) {
res.render('priceSearch',
{
priceSearch: result,
title: 'Product price search',
}
);
} else {
res.send("No documents found");
}
db.close();
});
}
});
});
module.exports = router;

req.query.price;
i added a stupid var to it

can I get the collections from robomongo to display it in a web page by nodeJS?

I want to display all the databases and their respective collections and documents from mongoDB in NodeJS

One approach is to use the listDatabases() method:
var Db = require('mongodb').Db,
MongoClient = require('mongodb').MongoClient,
Server = require('mongodb').Server,
ReplSetServers = require('mongodb').ReplSetServers,
ObjectID = require('mongodb').ObjectID,
Binary = require('mongodb').Binary,
GridStore = require('mongodb').GridStore,
Grid = require('mongodb').Grid,
Code = require('mongodb').Code,
BSON = require('mongodb').pure().BSON,
assert = require('assert');
var db = new Db('test', new Server('localhost', 27017));
// Establish connection to db
db.open(function(err, db) {
// Use the admin database for the operation
var adminDb = db.admin();
// List all the available databases
adminDb.listDatabases(function(err, dbs) {
assert.equal(null, err);
assert.ok(dbs.databases.length > 0);
db.close();
});
});
Collections can be listed with collectionNames:
var MongoClient = require('mongodb').MongoClient,
format = require('util').format;
MongoClient.connect('mongodb://127.0.0.1:27017/test', function(err, db) {
if(err) throw err;
db.collectionNames(function(err, collections){
console.log(collections);
});
});
You could also use MongooseJS within node.js to expose the MongoDB-Native Object that will list all the databases and their respective collections
In node.js, install Mongoose as follows:
$ npm install mongoose
Now you can use the mongoose object to connect to MongoDB and map out all collections within the databases:
var mongoose = require('mongoose'),
url = 'mongodb://localhost/test';
mongoose.connect(url);
mongoose.connection.on('open', function(){
mongoose.connection.db.collectionNames(function(error, names) {
if (error) {
throw new Error(error);
} else {
names.map(function(name) {
console.log('found collection %s', name);
});
}
});
});
mongoose.connection.on('error', function(error){
throw new Error(error);
});

var Db = require('mongodb').Db,
Server = require('mongodb').Server
var db = new Db('test', new Server('localhost', 27017));
db.open(function (err, db) {
var adminDb = db.admin();
adminDb.listDatabases(function (err, dbs) {
if (err) console.log(err);
else console.log(dbs.databases);
var data = dbs.databases;
data.forEach(function (res) {
if (res.name == "node_REST") {
console.log(res);
}
})
db.close();
});
});

How do I create a new database using the MongoDB Node.JS driver?

How do I programmatically create a database using the MongoDB Node.JS driver?
This looks promising, but I'm not sure how to connect to with the admin credentials and create a new database.
var db = new Db('test', new Server('locahost', 27017));
// Establish connection to db
db.open(function(err, db) {
assert.equal(null, err);
// Add a user to the database
db.addUser('user3', 'name', function(err, result) {
assert.equal(null, err);
// Authenticate
db.authenticate('user3', 'name', function(err, result) {
assert.equal(true, result);
// Logout the db
db.logout(function(err, result) {
assert.equal(true, result);
// Remove the user
db.removeUser('user3', function(err, result) {
assert.equal(true, result);
db.close();
});
});
});
});
});

in mongodb databases and collections are created on first access. When the new user first connects and touches their data, their database will get created then.

This seems to work.
var Db = require('mongodb').Db,
Server = require('mongodb').Server;
var db = new Db('test', new Server('localhost', 27017));
db.open(function (err, db) {
if (err) throw err;
// Use the admin database for the operation
var adminDb = db.admin();
adminDb.authenticate('adminLogin', 'adminPwd', function (err, result) {
db.addUser('userLogin', 'userPwd', function (err, result) {
console.log(err, result);
});
});
});

Try as below:
var adminuser = "admin";
var adminpass = "admin";
var server = "localhost";
var port = 27017;
var dbName = "mydatabase";
var mongodb = require('mongodb');
var mongoClient = mongodb.MongoClient;
var connString = "mongodb://"+adminuser+":"+adminpass+"#"+server+":"+port+"/"+dbName;
mongoClient.connect(connString, function(err, db) {
if(!err) {
console.log("\nMongo DB connected\n");
}
else{
console.log("Mongo DB could not be connected");
process.exit(0);
}
});