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AWS Lambda Node.js. mysql Error "Cannot enqueue Query after invoking quit" on second call onwards:

I am currently creating an AWS Lambda resolver that utilizes Nodejs mysql library. Right now, my lambda is capable of executing a query to the database during the first invocation. However, on the subsequent invocations the error "Cannot enqueue Query after invoking quit" occurs. I am aware that it is something to do with the connection to the database but if I am not wrong, 'connection.query' should be making an implicit connection to the database. I am also calling the 'connection.end' within the callback. Could someone lend me a helping hand on this one?
Here is the Lambda index.js code:
/* Amplify Params - DO NOT EDIT
API_SIMPLETWITTERCLONE_GRAPHQLAPIENDPOINTOUTPUT
API_SIMPLETWITTERCLONE_GRAPHQLAPIIDOUTPUT
API_SIMPLETWITTERCLONE_GRAPHQLAPIKEYOUTPUT
AUTH_SIMPLETWITTERCLONEB1022521_USERPOOLID
ENV
REGION
Amplify Params - DO NOT EDIT */
const mysql = require("mysql");
// const util = require("util");
const config = require("./config.json");
const connection = mysql.createConnection({
host: config.dbhost,
user: config.dbuser,
password: config.dbpassword,
database: config.dbname,
});
// resolvers
const resolvers = {
Query: {
getAllUser: (event) => {
return getAllUser();
},
},
};
function executeQuery(sql, params) {
return new Promise((resolve, reject) => {
const queryCallback = (error, results) => {
if (error) {
console.log("Error occured during query: " + error.message);
connection.destroy();
reject(error);
} else {
console.log("Connected to database and executed query");
console.log("Results:", results);
connection.end((err) => {
if (err) {
console.log("there was an error closing database:" + err.message);
}
console.log("database closed");
resolve(results);
});
}
};
if (params) {
connection.query(sql, [...params], (error, results) => {
queryCallback(error, results);
});
} else {
connection.query(sql, (error, results) => {
queryCallback(error, results);
});
}
});
}
async function getAllUser() {
const sql = "SELECT * FROM User";
try {
const users = await executeQuery(sql);
return users;
} catch (error) {
throw error;
}
}
exports.handler = async (event) => {
// TODO implement
console.log("event", event);
console.log('DB connection var', connection);
const typeHandler = resolvers[event.typeName];
if (typeHandler) {
const resolver = typeHandler[event.fieldName];
if (resolver) {
try {
return await resolver(event);
} catch (error) {
throw error;
}
}
}
throw new Error("Resolver not found");
};

You are ending your connection during the first invocation. As a result, the second invocation does not have that connection anymore.
If you create the connection object during module import, do not .end() it in your invocation.
If you wish to .end() the connection object during invocation, you have to create it during invocation as well.

Nodejs async/await mysql queries

I have a nodejs project with the current structure below, I need to insert a registry on clients table and return the last inserted ID from this table so I can use it in a second table, but I need to wait until the insert is completed in clients table, before insert the client ID on my second table. I'm trying to use async/await, but I'm always getting a null value.
My MYSQL connection: db.model.js
const config = require('config');
const mysql = require("mysql");
const connection = mysql.createConnection({
host: config.get('mysql.host'),
user: config.get('mysql.user'),
password: config.get('mysql.password'),
database: config.get('mysql.database')
});
connection.connect(function (err) {
if (err) {
console.error(`MySQL Connection Error: ${err.stack}`);
return;
}
console.log(`MySQL connected successfully!`);
});
module.exports = connection;
My CLIENT model
const mysql = require("./db.model");
const Client = function(client) {
this.login = client.login;
};
Client.create = (newClient, result) => {
mysql.query("INSERT INTO clients SET ?", newClient,
(err, res) => {
if (err) {
console.log("error: ", err);
result(err, null);
return;
}
result(null, {
id: res.insertId,
...newClient
});
}
);
};
module.exports = Client;
this is the client controller (i'm trying to use async/await here)
const Client = require('../models/client.model');
exports.create = (login) => {
const client = new Client({
login: login
});
Client.create(client, async (err, data) => {
if(!err) {
return await data.id;
} else {
return false;
}
});
}
And this is another controller, where I want to use methods from my client controller:
const ClientController = require('../controllers/client.controller');
...
utils.connect()
.then(clt => clt.sub.create(data))
.then((sub) => {
let lastInsertedId = ClientController.create(sub.login);
// lastInsertedId always return null here,
// but I know ClientController return a value after some time.
// method below will fail because lastInsertedId cannot be null
TransactionController.transactionCreate(lastInsertedId,
sub.id,
sub.param);
})
.catch(error => res.send(error.response.errors))
any help appreciated.

File to create database connection
const config = require('config');
const mysql = require('mysql2');
const bluebird = require('bluebird');
const dbConf = {
host: config.dbhost,
user: config.dbuser,
password: config.dbpassword,
database: config.database,
Promise: bluebird
};
class Database {
static async getDBConnection() {
try {
if (!this.db) {
// to test if credentials are correct
await mysql.createConnection(dbConf);
const pool = mysql.createPool(dbConf);
// now get a Promise wrapped instance of that pool
const promisePool = pool.promise();
this.db = promisePool;
}
return this.db;
} catch (err) {
console.log('Error in database connection');
console.log(err.errro || err);
}
}
}
module.exports = Database;
Use connection to execute your native query
const database = require('./database');
let query = 'select * from users';
let conn = await dl.getDBConnection();
let [data, fields] = await conn.query(query);

So I'm still using only the npm mysql package, but now I transformed all my queries into promises like below, so I can just wait until all the queries are completed.
const create = (idCliente, transactionId, amount, status) => {
const sql = "INSERT INTO transactions SET ?";
const params = {
id_cliente: idCliente,
transaction_id: transactionId,
amount: amount,
status: status
};
return new Promise((resolve, reject) => {
pool.query(sql, params, (err, result) => {
if (err) {
return reject(err);
}
resolve(result);
});
});
};
then I use like this:
create(params)
.then((result) => {
//call more queries here if needed
})
.catch((err) => { });

You can use sync-sql package of npm for execute async queries.
https://www.npmjs.com/package/sync-sql
Here is an example of it:
const express = require('express')
const mysql = require('mysql')
const app = express()
var syncSql = require('sync-sql');
// Create Connection
const connect = {
host: 'localhost',
user: 'root',
password: '',
database: 'ddd_test'
}
const db = mysql.createConnection(connect)
db.connect((err) => {
if (err) {
throw err
}
console.log("Connected");
})
function getDbData(query) {
return syncSql.mysql(connect, query).data.rows
}
app.get("/getData", async (req, res, next) => {
let sql = 'SELECT * from registration';
res.json({
data:getDbData(sql)
});
})
app.listen(3000, () => {
console.log('App listening on port 3000!');
});

I want to take out the result from mysql's connection.query and save it in global scope chain in nodejs

I tried bringing out result by storing in variable current product. But I cant use it outside the function, so my array returns empty
var connection = mysql.createConnection({
host: config.config.mysql.opencart_local.host,
user: config.config.mysql.opencart_local.user,
password: config.config.mysql.opencart_local.password,
database: config.config.mysql.opencart_local.database
})
var query_current_products = 'select * from table;';
var current_products = [];
connection.connect(function(err) {
if (err) throw err;
console.log("Connected!");
connection.query(query_current_products, function (err, result) {
if (err) throw err;
//console.log(result);
current_products = result;
});
}
)
console.log(current_products);
enter image description here

Try to use async/await syntax to get your results
const mysql = require('mysql'); // or use import if you use TS
const util = require('util');
const conn = mysql.createConnection({
host: config.config.mysql.opencart_local.host,
user: config.config.mysql.opencart_local.user,
password: config.config.mysql.opencart_local.password,
database: config.config.mysql.opencart_local.database
});
var current_products = [];
//
var query_current_products = 'select * from table;';
(async function getProducts () => {
try {
const rows = await query( query_current_products);
console.log(rows);
current_products=rows;
} finally {
conn.end();
}
})()

use this code:
var query_current_products = 'select * from users';
var current_products = [];
function f() {
return new Promise(resolve => {
con.connect(function (err) {
if (err) throw err;
console.log("Connected!");
con.query(query_current_products, function (err, result) {
if (err) throw err
resolve(result);
});
});
})
}
async function asyncCall() {
current_products = await f();
console.log("outside callback : ", current_products);
}
asyncCall();

Exporting Mysql Connection in nodeJS

In my database.js I have
var Mysql = require('Mysql');
var Jwt = require('jsonwebtoken');
var bcrypt = require('bcrypt');
var supersecretkey = 'JMDub_Super_Secret_key';
var config = require('./config');
var signupErrors = require('./Signuperrors.js');
var sucessMsg = require('./SucessMessages.js');
var App_errors = require('./error.js');
var query = require('./queryDB.js');
var connection = Mysql.createConnection({
"host": "******",
"user": "****",
"password": "***",
"database": "***"
});
connection.connect(function(err) {
if (err) {
console.error('error connecting: ' + err.stack);
return;
}
console.log('connected as id ' + connection.threadId);
});
//Sign Up Methods
var createUser = function createwithCredentails(post,callback) {
bcrypt.hash(post.password, 10, function(err, hash){
//console.log('Cache Hash : +',hash);
var createUserQuery = connection.query('INSERT INTO users SET ?',{"email":post.email,"password":hash,"username":post.username},function(err,result){
if (err) {
if (err.code == 'ER_DUP_ENTRY') {
//console.log(err.code);
callback(signupErrors.error_5000);
}
else callback(App_errors.error_1003);
}
if (result) {
callback(sucessMsg.success_signup);
}
});
});
}
//connection.query('SELECT * FROM Users Where Username = '' AND Password = ''');
var validateUser = function ValidateUserWithUserNameAndPassword(post,callback) {
var UserCheckQuery = connection.query('SELECT * FROM users WHERE email="'+post.email+'"',function(err, results, fields) {
if (err){
console.log(err);
callback(App_errors.error_1000);
}
if (results.length == 1) {
//console.log(results[0].password,post.password);
var givenPassword = post.password;
var DBhash = results[0].password;
bcrypt.compare(givenPassword, DBhash,function(err, res) {
if (res) {
console.log('Password matched');
var token = Jwt.sign({"email":post.email,"username":post.username},supersecretkey, {
expiresIn: 60*60*5 // expires in 5 hours
});
callback({
message:{
"success":1,
"description":"sucessfully logged in - please cache the token for any queries in future",
"environment":"test",
"errorCode":null
},
"token":token
});
}
if (!res) {
console.log('password doesnt match');
callback(signupErrors.error_6000);
}
if (err) {
console.log('Error Comparing Passwords');
callback(App_errors.error_1004);
}
});
}
else{
callback(signupErrors.error_6000);
}
});
};
var isauthenticate = function isauthenticated(post,route,callback) {
if (post.headers.token) {
Jwt.verify(post.headers.token, supersecretkey, function(err, decoded) {
if (decoded) {
//console.log(decoded);
//From this part the user is Sucessully Authenticated and autherization params can be extracted from token if required
//Write Business Logic in future as per the requirement
//Operation 1 - Update Profile
//Profile Details consists of {1.first name 2.last name 3. profile pictur(base 64 encoded) 4.further settings in future that can be added to DB if required}
if (route == '/update-profile') {
query.updateProfile(connection,decoded.email,post.body,function(response) {
callback(response);
});
}
//callback({"message":"is a valid token"});
}
if (decoded == null) {
console.log('is not a valid token');
//callback(App_errors.error_1000);
}
if (err) {
console.log('error verifying token');
callback(App_errors.error_1000);
}
});
}
else{
callback(App_errors.error_1001);
}
};
module.exports = {
validateUser:validateUser,
createUser:createUser,
isauthenticate:isauthenticate,
connection:connection
}
I am exporting connection object to queryDB.js file. But when I try to log the exported connection object I get undefined object. Why is this happening?
When I pass connection object as function argument, everything works fine. Not sure why?
below is queryDB.js file
var errors = require('./error.js')
var Dbconnection = require('./Database.js').connection;
var updateProfile = function profiledata(connection,email,data,callback) {
console.log(Dbconnection);
if ((!data)|| (Object.keys(data).length < 1)) {
//console.log(data);
callback(errors.error_1001);
}
else{
callback({"message":"update Sucesss"});
//console.log(connection);
//var updateData = mapProfileDataTomodel(data);
//console.log(updateData);
connection.query('SELECT * FROM users WHERE email = "'+email+'"',function(err, result,feilds) {
if (err) throw err;
if (result) {
console.log(result);
}
});
}
}
var mapProfileDataTomodel = function mapProfileDataTomodel(data) {
var profileDataModel = {};
for (var key in data) {
//console.log('looping and mapping data');
if (data.firstname) {
profileDataModel.firstname = data.firstname;
}
if (data.lastname) {
profileDataModel.lastname = data.lastname;
}
if (data.profilepic) {
profileDataModel.profilepic = data.profilepic;
}
}
return profileDataModel;
}
module.exports = {
updateProfile:updateProfile
}
I have commented out connection object log via function arguments.
So, Why I am unable to get the connection object that is exported? But I used the same exported connection object in my app.js file. It did work fine there.

Using Node.js to connect to a REST API

Is it sensible to use Node.js to write a stand alone app that will connect two REST API's?
One end will be a POS - Point of sale - system
The other will be a hosted eCommerce platform
There will be a minimal interface for configuration of the service. nothing more.

Yes, Node.js is perfectly suited to making calls to external APIs. Just like everything in Node, however, the functions for making these calls are based around events, which means doing things like buffering response data as opposed to receiving a single completed response.
For example:
// get walking directions from central park to the empire state building
var http = require("http");
url = "http://maps.googleapis.com/maps/api/directions/json?origin=Central Park&destination=Empire State Building&sensor=false&mode=walking";
// get is a simple wrapper for request()
// which sets the http method to GET
var request = http.get(url, function (response) {
// data is streamed in chunks from the server
// so we have to handle the "data" event
var buffer = "",
data,
route;
response.on("data", function (chunk) {
buffer += chunk;
});
response.on("end", function (err) {
// finished transferring data
// dump the raw data
console.log(buffer);
console.log("\n");
data = JSON.parse(buffer);
route = data.routes[0];
// extract the distance and time
console.log("Walking Distance: " + route.legs[0].distance.text);
console.log("Time: " + route.legs[0].duration.text);
});
});
It may make sense to find a simple wrapper library (or write your own) if you are going to be making a lot of these calls.

Sure. The node.js API contains methods to make HTTP requests:
http.request
http.get
I assume the app you're writing is a web app. You might want to use a framework like Express to remove some of the grunt work (see also this question on node.js web frameworks).

/*Below logics covered in below sample GET API
-DB connection created in class
-common function to execute the query
-logging through bunyan library*/
const { APIResponse} = require('./../commonFun/utils');
const createlog = require('./../lib/createlog');
var obj = new DB();
//Test API
routes.get('/testapi', (req, res) => {
res.status(201).json({ message: 'API microservices test' });
});
dbObj = new DB();
routes.get('/getStore', (req, res) => {
try {
//create DB instance
const store_id = req.body.storeID;
const promiseReturnwithResult = selectQueryData('tablename', whereField, dbObj.conn);
(promiseReturnwithResult).then((result) => {
APIResponse(200, 'Data fetched successfully', result).then((result) => {
res.send(result);
});
}).catch((err) => { console.log(err); throw err; })
} catch (err) {
console.log('Exception caught in getuser API', err);
const e = new Error();
if (err.errors && err.errors.length > 0) {
e.Error = 'Exception caught in getuser API';
e.message = err.errors[0].message;
e.code = 500;
res.status(404).send(APIResponse(e.code, e.message, e.Error));
createlog.writeErrorInLog(err);
}
}
});
//create connection
"use strict"
const mysql = require("mysql");
class DB {
constructor() {
this.conn = mysql.createConnection({
host: 'localhost',
user: 'root',
password: 'pass',
database: 'db_name'
});
}
connect() {
this.conn.connect(function (err) {
if (err) {
console.error("error connecting: " + err.stack);
return;
}
console.log("connected to DBB");
});
}
//End class
}
module.exports = DB
//queryTransaction.js File
selectQueryData= (table,where,db_conn)=>{
return new Promise(function(resolve,reject){
try{
db_conn.query(`SELECT * FROM ${table} WHERE id = ${where}`,function(err,result){
if(err){
reject(err);
}else{
resolve(result);
}
});
}catch(err){
console.log(err);
}
});
}
module.exports= {selectQueryData};
//utils.js file
APIResponse = async (status, msg, data = '',error=null) => {
try {
if (status) {
return { statusCode: status, message: msg, PayLoad: data,error:error }
}
} catch (err) {
console.log('Exception caught in getuser API', err);
}
}
module.exports={
logsSetting: {
name: "USER-API",
streams: [
{
level: 'error',
path: '' // log ERROR and above to a file
}
],
},APIResponse
}
//createlogs.js File
var bunyan = require('bunyan');
const dateFormat = require('dateformat');
const {logsSetting} = require('./../commonFun/utils');
module.exports.writeErrorInLog = (customError) => {
let logConfig = {...logsSetting};
console.log('reached in writeErrorInLog',customError)
const currentDate = dateFormat(new Date(), 'yyyy-mm-dd');
const path = logConfig.streams[0].path = `${__dirname}/../log/${currentDate}error.log`;
const log = bunyan.createLogger(logConfig);
log.error(customError);
}

A more easy and useful tool is just using an API like Unirest; URest is a package in NPM that is just too easy to use jus like
app.get('/any-route', function(req, res){
unirest.get("https://rest.url.to.consume/param1/paramN")
.header("Any-Key", "XXXXXXXXXXXXXXXXXX")
.header("Accept", "text/plain")
.end(function (result) {
res.render('name-of-the-page-according-to-your-engine', {
layout: 'some-layout-if-you-want',
markup: result.body.any-property,
});
});