Develop Reference

MongooseError: Query was already executed:

I'm trying to update the document but the error says the query has already been executed.
MongooseError: Query was already executed: footballs.updateOne({ date: 'January 4' }, {})
app.post('/api/bookslot', async (req, res) => {
console.log(req.body);
try {
const token = req.headers['x-access-token'];
const decoded = jwt.verify(token, 'secret123');
const email = decoded.email;
const user = await UserModel.findOne({ email: email });
let sportname = req.body.selectedSport.toLowerCase();
const time = req.body.slotTime;
const seats = req.body.availableSeats - 1;
if (!sportname.endsWith('s')) {
sportname = sportname.concat('s');
}
const NewSlotModel = mongoose.model(sportname, slotSchema);
var update = {};
update[time] = seats - 1;
console.log(update);
const a = await NewSlotModel.updateOne(
{ date: req.body.slotDate },
{ $set: update },
function (err, success) {
if (err) return handleError(err);
}
);
return res.json({ status: 'ok' });
} catch (e) {
console.log(e);
res.json({ status: 'error' });
}
});
where am I going wrong?

You are using both async/await and callbacks in your code, causing mongoose to throw an error.
The actual effect of using them both is exactly the error type that you are receiving:
Query was already executed
Mongoose v6 does not allow duplicate queries.
Mongoose no longer allows executing the same query object twice. If
you do, you'll get a Query was already executed error. Executing the
same query instance twice is typically indicative of mixing callbacks
and promises, but if you need to execute the same query twice, you can
call Query#clone() to clone the query and re-execute it. See gh-7398
Duplicate Query Execution
To fix the issue, just remove the third argument from the await
NewSlotModel.updateOne
Making it:
const a = await NewSlotModel.updateOne(
{ date: req.body.slotDate },
{ $set: update }
);

Mongoose v6. Don't support callbacks any longer.. check the image.
const productCount = await Product.countDocuments((count) => count) BAD
const productCount = await Product.countDocuments(); GOOD

How do I properly route data through my Node API?

I have the following files:
My routes - where the orders_count route lives:
routes/index.js
const express = require('express');
const router = express.Router();
const transactionsController = require('../controllers/transactionsController');
const ordersController = require('../controllers/ordersController');
const ordersCountController = require('../controllers/ordersCountController');
router.get('/transactions', transactionsController);
router.get('/orders', ordersController);
router.get('/orders_count', ordersCountController);
module.exports = router;
I then have my orders count controller living in the controllers directory:
controllers/ordersCountController.js
const ordersCountService = require('../services/ordersCountService');
const ordersCountController = (req, res) => {
ordersCountService((error, data) => {
if (error) {
return res.send({ error });
}
res.send({ data })
});
};
module.exports = ordersCountController;
My controller then calls my order count service which fetches data from another API.
services/ordersService.js
const fetch = require('node-fetch');
// connect to api and make initial call
const ordersCountService = (req, res) => {
const url = ...;
const settings = { method: 'Get'};
fetch(url, settings)
.then(res => {
if (res.ok) {
res.json().then((data) => {
return data;
});
} else {
throw 'Unable to retrieve data';
}
}).catch(error => {
console.log(error);
});
}
module.exports = ordersCountService;
I'm trying to return the JSON response. I initially had it setup with requests but looking at the NPM site, it appears that it's depreciated so have been digging through how to use node-fetch.
I have tried both 'return data' and res.send({data}), but neither are solving the problem.
I am still new to this so I am likely missing something very obvious, but how come I am not sending the JSON back through so that it displays at the /api/orders_count endpoint?
I keep thinking I messed something up in my controller but have been looking at it for so long and can't seem to figure it out.
Any help would be greatly appreciated and if there is anything I can add for clarity, please don't hesitate to ask.
Best.

please learn promises and await syntax. life will be easier.
never throw a string. always prefer a real error object, like that : throw new Error('xxx'); that way you will always get a stack. its way easier to debug.
avoid the callback hell : http://callbackhell.com/
you need to decide if you want to catch the error in the controller or in the service. no need to do in both.
in the controller you call the service that way :
ordersCountService((error, data) => {
but you declare it like that :
const ordersCountService = (req, res) => {
which is not compatible. it should look like this if you work with callback style :
const ordersCountService = (callback) => {
...
if (error) return callback(error)
...
callback(null, gooddata);
here is an example to flatten your ordersCountService function to await syntax, which allows the "return data" you were trying to do :
const fetch = require('node-fetch');
// connect to api and make initial call
const ordersCountService = async (req, res) => {
const url = ...;
const settings = { method: 'Get'};
try {
const res = await fetch(url, settings);
if (!res.ok) throw new Error('Unable to retrieve data');
return await res.json();
} catch(error) {
console.log(error);
}
}
module.exports = ordersCountService;
in fact i would prefer to error handle in the controller. then this woud be sufficient as a service
const fetch = require('node-fetch');
// connect to api and make initial call
const ordersCountService = async () => {
const url = ...;
const settings = { method: 'Get'};
const res = await fetch(url, settings);
if (!res.ok) throw new Error('Unable to retrieve data');
return await res.json();
}
module.exports = ordersCountService;
then you can call this funtion like this :
try {
const data = await ordersCountService(req, res);
} catch(err) {
console.log(err);
}
//or
ordersCountService(req, res).then((data) => console.log(data)).catch((err) => console.error(err));

js doesnt execute extern function to recieve data from db

I'm trying to receive same version data from my MySQL (MariaDB) Server.
For better maintenance i created one connection Object to handle all database queries.
However when I query some data, it seems like it isn't executed in time, but later when the first await command appears.
dbControl.js :
var mysql = require('mysql');
function getConnection(){
let dbConnection = mysql.createConnection({
host: "localhost",
user: "root",
password: ""
});
dbConnection.connect(function (err) {
if (err) throw err;
});
this.get_version = function() {
let sql = 'SELECT * FROM versionControl ORDER BY id DESC LIMIT 1;'
dbConnection.query(sql, function (err, result) {
if (err) throw err;
console.log("vData:", result);
return result;
});
}
}
module.exports.getConnection = getConnection;
dataHandler.js:
const browserControl = require('./browserControl');
const dbControl = require('../db/dbControl');
const dbConnection = new dbControl.getConnection();
let versionData;
// Here it should be executed -->
versionData = dbConnection.get_version();
console.log(versionData);
async function get_something(){
// Here it is executed -->
const browser = await browserControl.startBrowser();
//......
}
There is a 3th file which simply controls the program. At the moment it just executes the function get_something() like:
const originData = require('./dataHandler.js');
let data = originData.get_something();
console.log(data);
P.s.: its all running with node, thanks in advance ;_)

Your get_something() is marked as async.
Call it with await get_something() or get_something().then(console.log).

Ok, I got a solution. The SQL query function returns a promise now and I created an extra "getVersion"-async-function which is waiting for the resolve of the promise. Thus the promise waits for the db answer and the rest waits until the promise is resolved.
the dataHandler.js now looks like this:
const browserControl = require('./browserControl');
const dbControl = require('../db/dbControl');
const dbConnection = new dbControl.getConnection();
async function getVersion() {
let versionData;
versionData = await dbConnection.get_version();
console.log(versionData);
}
getVersion();
async function get_something(){
const browser = await browserControl.startBrowser();
}
and the query-function now looks like this:
this.get_version = function() {
let sql = 'SELECT * FROM versionControl.lol_scraper ORDER BY id DESC LIMIT 1;'
return new Promise(resolve => {
dbConnection.query(sql, function (err, result) {
if (err) throw err;
console.log("vData:", result);
resolve(result);
})
});
P.s.: still open for smarter or more modern solutions ;_)

MongoDB reusable custom javascript module

I would like to create a local Javascript module I can "require" in other files to handle all MongoDB CRUD operations.
I wrote something as:
-- dbConn.js file --
require('dotenv').config()
const MongoClient = require('mongodb').MongoClient
const ObjectID = require('mongodb').ObjectID
let _connection
const connectDB = async () => {
try {
const client = await MongoClient.connect(process.env.MONGO_DB_URI, {
useNewUrlParser: true,
useUnifiedTopology: true
})
console.log('Connected to MongoDB')
return client
} catch (err) {
console.log(error)
}
}
exports.findOne = async () => {
let client = await connectDB()
if (!client) {
return;
}
try {
const db = client.db("Test_DB");
const collection = db.collection('IoT_data_Coll');
const query = {}
let res = await collection.findOne(query);
return res;
} catch (err) {
console.log(err);
} finally {
client.close();
}
}
exports.findAll = async () => {
let client = await connectDB()
if (!client) {
return;
}
try {
const db = client.db("Test_DB");
const collection = db.collection('IoT_data_Coll');
const query = {}
let res = await collection.find(query).toArray();
return res;
} catch (err) {
console.log(err);
} finally {
client.close();
}
}
Then in another file (not necessary inside Express app), say
-- app.js ---
const findAll = require('./dbConn').findAll
const findOne = require('./dbConn').findOne
findAll().then(res => JSON.stringify(console.log(res)))
findOne().then(res => JSON.stringify(console.log(res)))
I wonder if it is correct?
I have to close the connection after each method/CRUD operation?
I was trying to use IIF instead of ".then", as:
(async () => {
console.log(await findOne())
})()
But I receive a weird error saying that findAll is not a function.
What's wrong with it?
Thanks.

It really depends on your use case which isn’t clear If you are using Express or just stand alone and how frequent are you planning to run app.js
Either way your code is expensive, each time you reference dbCon.js you are opening a new connection to the database.
So you can fix app.js by only requiring dbCon.js once and use it..
The best practice is to ofcourse use connection pooling https://www.compose.com/articles/connection-pooling-with-mongodb/

Promises in JS: using Axios to write to mongoDB

I am struggling to get my head round Promises. I think i understand the concept but I am unable to get them to work on the backend.
I have read several stackoverflow posts. I still see a few which are only months old so I guess i am not the only one :)
Specifically, I need help on how I can pass the result of a resolved promise within my code. In the code below, I fetch a JSON file from the starwars api and want to write it onto a mongodb atlas collection.
I use axios.get, which returns a promise. I then resolve it using .then and then use insertOne on mongoDB collections.
On the frontend for e.g in React, it works as expected, where you use setState to change the state by using the setState within the .then function.
I don't understand why it doesn't work in the backend.
Could you please tell me what I need to change so I can get it to write to mongoDB atlas?
var axios = require("axios");
const MongoClient = require("mongodb").MongoClient;
var db;
const getData = () => {
return axios
.get("https://swapi.co/api/people/1")
.then(response => {
if (!response.data) throw Error("No data found.");
console.log(JSON.stringify(response.data)) **//This returns the data as expected.**
return JSON.stringify(response.data);
})
.catch(error => {
console.log(error);
throw error;
});
};
console.log(getData()); **// This returns {Promise <pending>}**
const client = new MongoClient(process.env.MONGODB_URL, {
useNewUrlParser: true,
useUnifiedTopology: true
});
// Connect to database and insert default users into users collection
client.connect(err => {
console.log("Connected successfully to database");
let d = {
name: "Luke Skywalker",
height: "172",
mass: "77",
hair_color: "blond",
skin_color: "fair",
eye_color: "blue"
};
db = client.db(process.env.DB_NAME);
db.collection("macroData").insertOne(d); //this works
db.collection("macroData").insertOne(getData); // this doesn't work as it still appears to be a promise
});

getData() returns a Promise, as you are well aware, so you have to wait on that promise to resolve. A straightforward approach would be to perform the insert once the data is available:
client.connect(err => {
// ...
getData().then(data => {
db.collection('macroData').insertOne(data)
})
})
Or, if you can use async/await:
client.connect(async err => {
// ...
const data = await getData()
db.collection('macroData').insertOne(data)
})

Your mongodb call needs to be within the axios promise, that way the resolved promise can be used to feed your database. That's what held me up for a while...
The code below is for Nick comment, I couldn't post the code in the comment as it was too long. You should have a database named test or appropriate name here let datab = client.db('test'), i think it comes by default when you create a mongodb atlas.
if you change your user and password in the mongourl, you should be good to go.
Hope that helps. This creates a starwars entry under test.starWarsData .. hope t
let axios = require("axios");
let MongoClient = require("mongodb").MongoClient;
let mongoParams = { useNewUrlParser: true, useUnifiedTopology: true };
let mongoUrl =
"mongodb+srv://user:password#cluster0-hnc4i.azure.mongodb.net/test";
//try feeding just the object e, and see if it works, in case your axios error catching is not great.
let e = {
a: "this is a",
b: "this is b",
c: "this is c",
d: "this is d"
};
let newUrl = "https://swapi.co/api/people/1";
console.log(newUrl);
let client = new MongoClient(mongoUrl, mongoParams);
client.connect(err => {
if (err) {
console.log(err.message);
throw new Error("failed to connect");
}
let datab = client.db("test");
console.log("db connected");
try {
axios.get(newUrl).then(res => {
try {
datab.collection("starWarsData").insertOne(res.data);
console.log("insert succeeded");
} catch (err) {
console.log("insert failed");
console.log(err.message);
}
});
} catch (err) {
throw Error("axios get did not work");
}
});