NodeJs Connection Error querying SQL Server - sql-server

Question

I am using this code to connect to my SQL Server and retrieve some data which works fine, if I only call the code once. If I call it twice I get this error:
ConnectionError: Already connecting to database! Call close before connecting to different database.at ConnectionPool._connect
But I am closing the conn after the call so I'm not sure what I am missing.
var sql = require('mssql');
const pool = new sql.ConnectionPool({
user: 'sa',
password: 'password',
server: '192.168.1.2',
database: 'demo',
options: {
encrypt: false
}
})
var conn = pool;
module.exports.getCounter = function( query){
conn.connect().then(function (err) {
var req = new sql.Request(conn);
req.query(query).then(function (result) {
console.log(result.recordset);
return result.recordset;
conn.close();
})
.catch(function (err) {
console.log(err);
conn.close();
});
})
.catch(function (err) {
console.log(err);
})};

Answer 1

You're returning the value before closing the connection, hence the function terminates before reaching that line. So just move the return statement below your conn.close(). The other issues you might have afterwards is that you might be calling your function twice before one executes and terminates completely, since those calls are asynchronous.
You might have to set your getCounter function as a Promise, so that you can wait for its completion/failure before calling it again. Off the top of my head in your example:
const getCounter = () => new Promise((resolve,reject) => {
conn.connect().then(function (err) {
var req = new sql.Request(conn);
req.query(query).then(function (result) {
conn.close();
resolve(result);
})
.catch(function (err) {
conn.close();
reject(err);
});
})
})
You can call your function afterwards as getCounter().then((result) => {...})

Answer 2

Here is another way to solve it which might be helpful for others.
const sql = require('mssql')
let connectionPoolConfig = {
user: 'sa',
password: 'password',
server: '192.168.1.2',
database: 'demo',
options: {
encrypt: false
}
}
let connectionPoolPromise = null
let connectionPoolObj = null
let getOrCreatePool = async () => {
if (connectionPoolObj) {
return connectionPoolObj
} else if (!connectionPoolPromise) {
connectionPoolPromise = new sql.ConnectionPool(connectionPoolConfig).connect()
}
connectionPoolObj = await connectionPoolPromise
return connectionPoolObj
}
let query = async(sql) => {
const pool = await getOrCreatePool()
return await pool.request().query(sql)
}
module.exports = {
query: query
}
And here is how to call it
let testCallerSQL = async () => {
try {
const res = await sqlUtil.query('select * from mytable')
console.log(res.recordset)
} catch(err) {
console.log(err)
} finally {
}
}