CODEWITHSUNDEEP
mysqlnode.jsamazon-web-servicesaws-lambdadatabase-connection
Kunal Choudhary
Kunal Choudhary

Reputation: 21

What is the right way to close the Database connection (Mysql) using Node.js and written inside AWS lambda

I am using the finally block written in node.js to close the database connection i have opened in the code. The code snippet is attached below.

Problem i am facing :- When i execute the below code on local machine, my finally blocks gets executed and this gets consoled "Response after dbconnection close:".

But when i am executing it in AWS lambda, i get response from my last then block and when my finally block executes it does not console the "Response after dbconnection close:" in function logs.

So the connection remains open.

It gets closed when i hit the lambda function again. but leaves behind the Open connection from the latest execution.

Please let me know how to use finally block properly or shall i close the connection in last then block?

exports.executeSelectQueryPromise = (sql, args, parameters) => {

    sql = " SELECT * FROM ( " + sql + " ) as dataTable ";

    let DBConnection;

    return mysql.createConnection(process.env)
    .then(async (conn) => {
        DBConnection = conn;

        return DBConnection.query(sql, args);
    }).then(async (rows) => {
        let result = {
            "statusCode": 200,
            "headers": {
                "Access-Control-Allow-Origin": "*"
            },
            "body": [],
            "isBase64Encoded": false
        }

        return result;
    }).catch(async (error) => {
        console.log("Error: ", error);
        let err = {
            "statusCode": 400,
            "headers": {
                "Access-Control-Allow-Origin": "*"
            },
            "body": [],
            "isBase64Encoded": false
        }
        return err;
    })
    .finally(async () => {        
        
        console.log("DB connection type: ", typeof DBConnection);
        if (DBConnection && DBConnection.end) {
            DBConnection.end()
            .then(res => console.log("Response after dbconnection close: ", res))
            .catch(e => console.log("Error in dbconnection close: ", e));
        }
    });
}

Upvotes: 0

Views: 430

Answers (1)

Muhammad Arsalan Hassan
Muhammad Arsalan Hassan

Reputation: 597

A much better practice is to close your connection soon after the query gets executed irrespective of being executed successful or unsuccessful.

Upvotes: 1

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