How to reconnect SQL Server tedious when connection is lost - node.js

Question

js and using tedious to connect. Connection is successful and I'm able to connect. However in period of time I would lose connect and receive these errors in Azure.
RequestError: Requests can only be made in the LoggedIn state, not the Final stateat RequestError (D:\home\site\wwwroot\node_modules\tedious\lib\errors.js:32:12)
at Connection.makeRequest (D:\home\site\wwwroot\node_modules\tedious\lib\connection.js:2380:49)at Connection.execSql (D:\home\site\wwwroot\node_modules\tedious\lib\connection.js:2034:10)at submitCode (D:\home\site\wwwroot\controller\mssqlController.js:121:16)at Layer.handle [as handle_request] (D:\home\site\wwwroot\node_modules\express\lib\router\layer.js:95:5)at next (D:\home\site\wwwroot\node_modules\express\lib\router\route.js:137:13)at Route.dispatch (D:\home\site\wwwroot\node_modules\express\lib\router\route.js:112:3)at Layer.handle [as handle_request] (D:\home\site\wwwroot\node_modules\express\lib\router\layer.js:95:5)at D:\home\site\wwwroot\node_modules\express\lib\router\index.js:281:22at Function.process_params (D:\home\site\wwwroot\node_modules\express\lib\router\index.js:335:12) {code: 'EINVALIDSTATE'}[0mPOST /login [32m200 [0m11.820 ms - 27[0m
Here is my code:
let config = {
server: '',
authentication: {
type: 'default',
options: {
userName: '',
password: ''
}
},
options: {
// If you are on Microsoft Azure, you need encryption:
encrypt: true,
database: ''
}
};
let connection = new Connection(config);
connection.on('connect', function (err) {
// If no error, then good to proceed.
console.log("err", err);
});
let Request = require('tedious').Request
let TYPES = require('tedious').TYPES;
My question is where and what can I add to reconnect or reset SQL Server in Azure if connection is lost?

Answer 1

You can try using the below code to retry the connection:
let intervalFunction;
const INTERVAL_DURATION = 4000;
if (require.main === module){
console.log("Listening on http://localhost:" + config.port + " ...");
app.listen(config.port);
// try to connect to db and fire main on succes.
intervalFunction = setInterval(()=> getConnection(), INTERVAL_DURATION);
}
function getConnection() {
sql.close();
sql.connect(config.database).then(() => {
sql.close();
clearInterval(intervalFunction);
main();
}).catch(function(err) {
console.error(err);
console.log(`DB connection will be tried again in ${INTERVAL_DURATION}ms`)
sql.close();
});
}
Once the initial connection has been made but it got lost in the meantime, then the pool will pick up the connection automatically and handle your connections.

Answer 2

I suggest using the mssql node package, which still uses tedious, and using a pool -- which will auto-reconnect.
https://www.npmjs.com/package/mssql#connections-1
Otherwise, you can look for connection.on('end') event, or error event, and write a custom function to retry the connection then. See an example of listening here: https://github.com/tediousjs/tedious/blob/master/examples/simple-client.js