Node.js Lambda Async return Undefined - node.js

Question

Simple call to ec2 Describing Security groups and returning the security group ID. Using Async / await, but when logging the return value, I get undefined. I fully admit I'm coming from Python and I've tried my hardest to wrap my brain around async calls. I thought I had it nailed, but I'm obviously missing something.
'use strict';
// Load Modules
const AWS = require('aws-sdk')
//Set the region
AWS.config.update({region: 'us-west-2'});
// Call AWS Resources
const ec2 = new AWS.EC2();
// Get Security Group ID From Event
const getSgIdFromEvent = async (event) => {
var ec2params = { Filters: [{Name: 'tag:t_whitelist',Values[event['site']]}]};
await ec2.describeSecurityGroups(ec2params, function (err, response) {
if (err) {return console.error(err.message)}
else {
var sgId = response.SecurityGroups[0].GroupId;
return sgId;
};
});
};
// MAIN FUNCTION
exports.handler = (event, context) => {
getSgIdFromEvent(event)
.then(sgId => {console.log(sgId)});
}
"sgId" should return the security group ID. It does print out fine in the original function before the return.

Answer 1

Typically if it is an async call you want you handle it similar to this way without using a callback
// Load Modules
const AWS = require('aws-sdk')
//Set the region
AWS.config.update({ region: 'us-west-2' });
// Call AWS Resources
const ec2 = new AWS.EC2();
// Get Security Group ID From Event
const getSgIdFromEvent = async (event) => {
var ec2params = { Filters: [{ Name: 'tag:t_whitelist', Values[event['site']]}] };
try {
const securityGroupsDesc = await ec2.describeSecurityGroups(ec2params).promise();
const sgId = securityGroupsDesc.SecurityGroups[0].GroupId;
//do something with the returned result
return sgId;
}
catch (error) {
console.log('handle error');
// throw error;
}
});
};
// MAIN FUNCTION
exports.handler = (event, context) => {
getSgIdFromEvent(event)
.then(sgId => { console.log(sgId) });
}
however if it doesn't support async you just use the callback to handle the returned data or error without using async function.However Reading into AWS docs you can find that the function ec2.describeSecurityGroups() returns an AWS Request
which has a method promise() that needs to be invoked to send the request and get a promise returned.Note that the try catch here is not needed but good to have in case error occurs during the process.

Answer 2

As I said in the comment, chance are that describeSecurityGroups doesn't return a Promise. Try transforming it explictly in a Promise instead:
const promiseResponse = await new Promise((res, rej) => {
ec2.describeSecurityGroups(ec2params, function (err, response) {
if (err) {return rej(err.message)}
else {
var sgId = response.SecurityGroups[0].GroupId;
res(sgId);
};
})
});
// promiseResponse is now equal to sgId inside the callback
return promiseResponse; // this will work because the function is async
Note: You can drop the else keyword

Answer 3

Here is the code that worked using async / await. Thanks to #Cristian Traina I realized ec2.describeSecurityGroups wasn't returning a promise, it was returning an AWS.Event.
// Get Security Group ID From Event
const getSgIdFromEvent = async (event) => {
console.log('Getting Security Group ID')
var params = { Filters: [{Name: 'tag:t_whitelist', Values
[event['site']]}]};
const describeSG = await ec2.describeSecurityGroups(params).promise();
return describeSG.SecurityGroups[0].GroupId;
};
// Get Ingress Rules from Security Group
const getSgIngressRules = async (sgId) => {
console.log(`Getting SG Ingress rules for ${sgId}`)
var params = { GroupIds: [ sgId]};
try{
const ingressRules = await ec2.describeSecurityGroups(params).promise();
return ingressRules;
}
catch (error) {
console.log("Something went wrong getting Ingress Ruls");
}
};
// MAIN FUNCTION
exports.handler = (event, context) => {
getSgIdFromEvent(event)
.then(sgId => {return getSgIngressRules(sgId);})
.then(ingressRules => {console.log(ingressRules);});
}
I submitted this as the answer now since the getSgIdFromEvent function I have, is only 8 lines and still using the async/await like I was desiring.
What I was missing was the .promise() on the end of the function and returning that promise.
Thanks for all the responses!