Lambda function returns null from nested async function

Question

The Lambda function is not hitting the memory limit neither timing out. I read somewhere that it may return because the event loop is empty but I have context.callbackWaitsForEmptyEventLoop set to false.

Here is the function:

module.exports.callMenu = (event, context, callback) => {

  context.callbackWaitsForEmptyEventLoop = false;
  const eventJSON = qs.parse(event.body);
  myMongooseObject.findOne({ value: eventJSON.value }, (err, theObject) => {
    if (!err) {

      newObj = new myMongooseObject();
      newObj.message = 'this worked';

      newObj.save((err) => {
        if (!err) {
          callback(null, { body: 'success' });
        } else {
          console.log(err);
        }
      });
    }
};

The functions returns nothing. Do you expect that the callback is called with a specific value? And where do you define "myMongooseObject" and "newCall"? — Steffen Schmitz
– Steffen Schmitz, Commented Jul 5, 2017 at 21:53
I don't understand your question the function should return body:'success' — loag
– loag, Commented Jul 5, 2017 at 21:58
Based on the code you provided I would expect the function to fail with "Cannot read property findOne of undefined". myMongooseObject is defined nowhere. And if the .findOne function returns an error it will also run into a timeout. If you add a more solid error handling you may be able to find the issue. — Steffen Schmitz
– Steffen Schmitz, Commented Jul 5, 2017 at 22:13
ok I'm sorry i didn't make it clear that I have that defined and it is returning no errors I figured that would be understood because of what my question was. It doesn't return any errors it just returns null if the callback is inside the save. however it does not return null when outside of the save. — loag
– loag, Commented Jul 5, 2017 at 22:23
Does the save return an error? If it does callback is never called and the lambda function returns null by default. — Steffen Schmitz
– Steffen Schmitz, Commented Jul 5, 2017 at 22:25

Zanon · Accepted Answer · 2017-07-05 22:27:34Z

In your code, you are not adding callbacks for when there is an error in the request. And you may want to add a try/catch to handle any other issues with your code.

Also, you don't need to set callbackWaitsForEmptyEventLoop because you are not adding extra events besides your main request.

Try this:

const myMongooseObject = defineThisObject(); // maybe you forgot to define it
const qs = defineThisObjectToo(); // maybe another error

module.exports.callMenu = (event, context, callback) => {

    try {
        const eventJSON = qs.parse(event.body);
        myMongooseObject.findOne({ value: eventJSON.value }, (err, theObject) => {

            if (!err) {
                newObj = new myMongooseObject();
                newObj.message = 'this worked';

                // define the newCall object too?

                newCall.save((err) => {
                    if (!err) {
                        callback(null, { body: 'success' });
                    } else {
                        callback(err); // add this
                    }
                });
            } else {
                callback(err); // add this
            }
        });
    } catch (e) {
      callback(e);
    }
};

Collectives™ on Stack Overflow

Lambda function returns null from nested async function

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related