Why is there no output shown in the logs for this simple Lambda function

Question

This is a lambda function with Node.js 14.x The only log I am seeing is this one : console.log(event); None of the ones after it show up. The response is also returned as null. Waht is wrong with my code?

    var AWS  = require("aws-sdk");
    var lambda = new AWS.Lambda();

    exports.handler = async function(event, context, callback) {
    
    var params = {
            FunctionName: 'Myfunction', 
            Qualifier: 'v1' 
    };
    console.log(event);
    
    var x =lambda.getProvisionedConcurrencyConfig(params, function(err, data) {
        console.log('entered call');
        if (err){
            console.log('error occured');
            console.log(err, err.stack); 
            response = {
                statusCode: 200,
                body: JSON.stringify(err),
            };
        } 
        else{
            console.log('Success');
            response = {
                statusCode: 200,
                body: JSON.stringify(data),
            };
        console.log(data);          

        }    
    });
    return response;
};

Answer 1

Your function finish immediately, before getProvisionedConcurrencyConfig finish. You use callback style for your function async function(event, context, callback), but the callback function never be called.

The first solution is keeping the callback style, and you have to call the callback function:

var AWS = require("aws-sdk");
var lambda = new AWS.Lambda();

exports.handler = function (event, context, callback) { // dont mix callback with async

  var params = {
    FunctionName: 'Myfunction',
    Qualifier: 'v1'
  };
  console.log(event);

  lambda.getProvisionedConcurrencyConfig(params, function (err, data) {
    console.log('entered call');
    if (err) {
      console.log('error occured');
      console.log(err, err.stack);
      callback(null, { // the function will finish with success status
        statusCode: 200,
        body: JSON.stringify(err),
      });
    }
    else {
      console.log('Success');
      console.log(data);
      callback(null, {
        statusCode: 200,
        body: JSON.stringify(data),
      });
    }
  });
};

The second solution is using Promise style for the function(recommendation):

var AWS = require("aws-sdk");
var lambda = new AWS.Lambda();

exports.handler = async function (event) { // keep as async

  var params = {
    FunctionName: 'Myfunction',
    Qualifier: 'v1'
  };
  console.log(event);

  try {
    console.log('entered call');
    // wait until it completed
    const data = await lambda.getProvisionedConcurrencyConfig(params).promise(); // convert to a promise
    console.log('Success');
    console.log(data);
    return {
      statusCode: 200,
      body: JSON.stringify(data),
    };
  } catch (err) {
    return { // the function will finish with success status
      statusCode: 200,
      body: JSON.stringify(err),
    };
  }
};