AWS Lambda using Asynchronous code returns NULL

Question

This question is a follow up question, the link to the other question is -- aws lambda function async connection query

I am developing server code using AWS Lambda and to test the asynchronous connection I am using the same code provided by Trung with improvement by giankotarola and the output of the Lambda Function comes only if I replace --

1. return callback(null, {body: JSON.stringify(result),statusCode:200});

with --

2. return result;

Also, at the following line --

3. pool.getConnection((err, connection) => {

It gives a warning: Expected Error to be handled

I cannot understand why the code at Line 1. mentioned above doesn't work ? And how to handle the warning at 3.

It would be helpful if you can post some code directly here as part of the question. — Arun Kamalanathan
– Arun Kamalanathan, Commented Feb 15, 2020 at 3:16

Jason Wadsworth · Accepted Answer · 2020-02-15 03:18:03Z

1

The first issue is because the function is using async. With async functions you just return the result. The callback is used when you are not using async.

I believe the second issue is because the err on that call isn't handled. There is a handler for the second err, but not this one. Basically that code should look like this:

let getOrder = async (sql, params) => {
    return new Promise((resolve, reject) => {
        pool.getConnection((err, connection) => {
            if (err){
                reject(err);
            }
            else {
                connection.query(sql, params, (err, results) => {
                    if (err){
                        reject(err);
                    }
                    else {
                        console.log("-----Query Done!");
                        connection.release();
                        console.log("-----Data: ", results);
                        resolve(results);
                    }
                }
            });
        });
    });
};

answered Feb 15, 2020 at 3:18

Jason Wadsworth

8,99026 silver badges38 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Vinit Kumar Over a year ago

Thank you Jason. I did not see the error handling for the second part. After handling the err, the warning disappears.

Collectives™ on Stack Overflow

AWS Lambda using Asynchronous code returns NULL

1 Answer 1

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related