NodeJS MSSQL multiple queries promised - sql-server

Question

I have a lot of problem using the mssql npm library.
Here is my db class :
"use strict"
const mssql = require('mssql');
const moment = require("moment");
let pool_historian = null;
let connexion_historian = null;
function mapBarChart(array) {
return new Promise((resolve, reject) => {
let result = {}
result.old = []
result.this = []
let currentYear = null;
for (let i = 0; i < array.length; i++) {
if (parseInt(moment().format("YYYY")) !== array[i].Annees) {
result.old.push(array[i]);
} else {
result.this.push(array[i]);
}
}
resolve(result);
})
};
class Historian {
constructor(data) {
pool_historian = new mssql.ConnectionPool({
server: data.host,
user: data.username,
password: data.password,
database: data.historian_db,
pool: {
max: 50,
min: 1
}
});
}
getBarChart(sensor, from, to) {
return pool_historian.connect().then(connector => {
return connector.query`SELECT Annees=YEAR(DateTime),Mois=MONTH(DateTime), Valeur=ROUND(sum(AnalogHistory.Value),2) FROM AnalogHistory WHERE AnalogHistory.TagName IN (${sensor}) AND Quality = 0 AND wwVersion = 'Latest' AND wwRetrievalMode = 'Full' AND DateTime >= ${from} AND DateTime <= ${to} AND AnalogHistory.Value > 0 GROUP BY YEAR(AnalogHistory.DateTime),MONTH(AnalogHistory.DateTime) ORDER BY Annees, Mois`.then(result => {
connector.close();
return mapBarChart(result.recordset).then(result => { return result });
//return result.recordset;
}).catch(err => {
return err;
})
})
}
getLineChart() {
return pool_historian.connect().then(connector => {
let variable = "A_000000000000000000000000000045.PV";
return connector.query`SELECT Annees=YEAR(DateTime),Mois=MONTH(DateTime),day=DAY(DateTime), Valeur=ROUND(sum(AnalogHistory.Value),2) FROM AnalogHistory WHERE AnalogHistory.TagName IN (${variable}) AND Quality = 0 AND wwVersion = 'Latest' AND wwRetrievalMode = 'Cyclic' AND DateTime >= '20160101 00:00:00.000' AND DateTime <= '20170809 00:00:00.000' AND AnalogHistory.Value > 0 GROUP BY YEAR(AnalogHistory.DateTime),MONTH(AnalogHistory.DateTime), Day(AnalogHistory.DateTime)ORDER BY Annees, Mois`.then(result => {
connector.close();
return result.recordset;
}).catch(err => {
return err;
})
})
}
close() {
pool_historian.close()
}
}
This class is used in this "business class" :
const Historian = require(`${__dirname}/historian-query`)
const Fdedb = require(`${__dirname}/fdedb-query`)
const moment = require('moment');
moment.locale("fr-FR");
class Graph_Tasks {
constructor() {
this.historian = new Historian({ host: "192.168.1.16", username: "******", password: "w***", historian_db: "R******e" })
this.fdedb = new Fdedb({ host: "192.168.1.16", username: "*****", password: "*****", fde_db: "S*****" })
}
createGraphForBuilding(code) {
return new Promise((resolve, reject) => {
this.fdedb.getList(code).then(list => {
console.log(list)
let datas = [];
//Foreach item on the list perform these 2 queryes
Promise.all([this.historian.getLineChart("A_000000000000000000000000000045.PV", moment().subtract(1, "years").startOf("year").format(), moment().format()), this.historian.getBarChart("A_000000000000000000000000000045.PV", moment().subtract(1, "years").startOf("year").format(), moment().format())]).then(results => {
let datas = []
datas = { "lineChart": null, "barChart": results[0] };
console.log(datas)
res.render('index', { title: 'WebGraph', message: 'Yo Yo', datas });
})
console.log(datas)
resolve(datas)
}).catch(console.log);
});
}
}
module.exports = Graph_Tasks;
As you can see, what I'm trying to do is performing a simultaneous database request. As I read in the documentation, the connection pool must let me do this properly. So when the program arrives at Promise.all, I expected that the 2 requests will be launched simultaneously.
But I get an error :
Une exception s'est produite : Error
Promise Rejection (ConnectionError: Already connecting to database! Call close before connecting to different database.)
ConnectionError: Already connecting to database! Call close before connecting to different database.
at ConnectionError (d:\repositories\fde\node_modules\mssql\lib\base.js:1428:7)
at ConnectionPool._connect (d:\repositories\fde\node_modules\mssql\lib\base.js:235:23)
at EventEmitter.connect.PromiseLibrary (d:\repositories\fde\node_modules\mssql\lib\base.js:217:19)
at ConnectionPool.connect (d:\repositories\fde\node_modules\mssql\lib\base.js:216:12)
at Historian.getBarChart (d:\repositories\fde\class\historian-query.js:39:31)
at __dirname.createGraphForBuilding.Promise.fdedb.getList.then.list (d:\repositories\fde\class\graph_tasks.js:21:188)
at process._tickCallback (internal/process/next_tick.js:109:7)
So my question is: how to adapt the code to let me perform several queries at the same time (the promise.all for each of my list item)?

Answer 1

The issue is that you can't open multiple connection pools to the same server (I assume Fdedb is opening another connection because you didn't include code for it). If, say, you were pulling that data from two different servers then opening two connection pools would be appropriate- I've run into that use case before. But it looks like your two databases are on the same server (localhost), so it's better to open just the one connection and pass it to your objects to make the query. You can touch multiple databases on the same host using plain old SQL, see: How do I query tables located in different database?