Global connection already exists issue node.js - sql-server

Question

I have connected MSSQl with node.js using below code
var sql = require('mssql')
var config ={
server:'xxxx',
database:'xxxx',
user:'xxx',
password:'xxx',
port:'xx'
};
sql.connect(dbconfig, function (err) {
if (err) console.log(err);
var sqlquery='';
const request = new sql.Request();
if(condition)
{
//query to the database and get the repo value
sqlquery='select * from verylargetable';
request.query(sqlquery, function (err, result) {
if (err) console.log(err)
var repo=result.recordset[0].Repo;
//query to the database and get the comm value
sqlquery="select commit from verylargetable where Repo='"+repo+"'";
request.query(sqlquery, function (err, result) {
if (err) console.log(err)
var comm=result.recordset[0].Comm;
if (result.recordset.length > 0)
{
//query to the database and update the table
sqlquery="UPDATE verylargetable set Repo='"+repo+"', WHERE Comm='"+comm+"'";
request.query(sqlquery, function (err,result){
if (err) console.log(err)
console.log("record(s) updated");
});
}
});
});
}
else
{
//query to the database and get the repo value
sqlquery='select * from verylargetable';
request.query(sqlquery, function (err, result) {
if (err) console.log(err)
var repo=result.recordset[0].Repo;
//query to the databaseto insert new record
sqlquery ="INSERT INTO verylargetable VALUES("+repo+"','"+comm+"',1)";
request.query(sqlquery, function (err, result) {
if (err) console.log(err)
});
});
}
});
Based on some conditions have to execute queries. while executing, these queries are updated properly.but sometimes facing below issue
global connection already exists. call sql.close() first.
when i used sql.close() at the end i couldn't initialize connection next time.
Facing connection is closed issue.
I have separate method for database changes.I need to establish the connection at the start of the method and have to close at the end.In between have to execute all the queries.
please let me know how to open and close the connection properly?

Answer 1

sql.connect returns connection, in order to close the connection, just call close on the result.
var pool = sql.connect(dbconfig, function (err) {
if (err) console.log(err);
const request = new sql.Request()
var sqlquery='select * from verylargetable';
request.query(sqlquery, function (err, result) {
if (err) console.log(err)
});
});
pool.close();

Answer 2

I was facing the same issue and solved it with below implementation,
For handling global connection already exists. call sql.close() first we need to create a connection pool for mssql npm version 4.0.4
const config = {
user: '**',
password: '**',
server: '** or localhost',
database: '**',
pool: {
max: 10,
min: 0,
idleTimeoutMillis: 30000
}}
router.get('/SQLConnection1', function (req, res, next) {
const pool1 = new sql.ConnectionPool(config, err => {
// ... error checks
// Query
pool1.request() // or: new sql.Request(pool1)
.query('SELECT ID,Name from Avatar', (err, result) => {
// ... error checks
console.dir(result)
res.json({'Result': result})
})
})
pool1.on('error', err => {
// ... error handler
console.log('Error ' + err);
})
});