AWS Lambda doesn't work with `async`, Only with callbacks?

Question

I have a Lambda function in AWS using Node 8.1 which initiate MSSQL request ( to an external server , which is not in aws)

When I'm using the non async handler with non async code (but callbacks )—

exports.handler = (event, context, callback) => {...}

— Everything is OK.

Proof: For this code, which uses callbacks-

exports.handler = (event, context, callback) => {
     sql.connect(config, err => {
        if (err) {
          callback(err);
        } else {
          const req = new sql.Request();
          req.query(
            'select * from img.dbo.images where imageid = 1641',
            (error, result) => {
              if (error) {
                callback(error);
              } else {
                sql.close();
                callback(null, result.recordset);
              }
            }
          );
        }
      });
};

I get this response :

However , If I change the code to the async version :

exports.handler = async (event, context, callback) => {
  try {
    let pool = await sql.connect(config);
    let result1 = await pool
      .request()
      .query('select * from img.dbo.images where imageid = 1641');

    callback(null, result1.recordset);
  } catch (err) {
    callback(err);
  }
};

— I get a Timeout error(sure it's related to a non-fulfill promise) :

Question

Why doesn't the async version work ? how can I make it work?

James · Accepted Answer · 2019-02-17 23:30:04Z

4

Remove the callback param and just return the result instead. Also, you can avoid catching errors unless you need to do any special handling

exports.handler = async (event, context) => {
  const pool = await sql.connect(config);
  return await pool
    .request()
    .query('select * from img.dbo.images where imageid = 1641');
}

answered Feb 17, 2019 at 23:30

James

82.4k19 gold badges172 silver badges245 bronze badges

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

3 Comments

Royi Namir Over a year ago

Thanks. working. One question though , When an error occurs , should I return it ? or should I callback(error) it ? can you please provide a small example in this ^ code ?

James Over a year ago

@RoyiNamir forget callback() with async / await, if you want to catch the error then you should return it.

markmnl Over a year ago

thanks for this, i never came across anything offical to return request/response instead of using callback so was stuck as well

Collectives™ on Stack Overflow

AWS Lambda doesn't work with `async`, Only with callbacks?

1 Answer 1

3 Comments

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Related