Lambda function completes tasks and requests but fails to return to calling function

10 replies

Last updated: Jun 10, 2020

Hey folks! Bit of a random code question that I thought I might throw out there – Not Sanity related hence not in the 'Help" channel, but I need someone to bounce this off of, and this is probably the most engaged and helpful community of devs I know, so I thought it was probably worth posting here:
I’ve never had this issue before - A lambda function which completes its tasks, makes its requests and those requests return properly, but the lambda fails to return back to the calling function. The offending lambda function is as follows:

import axios from 'axios'

import { getAuth0AccessToken } from '../lib/getAuth0AccessToken'

exports.handler = async event => {
  if (!event.body) {
    return {
      statusCode: 400,
      body: JSON.stringify({
        statusCode: 400,
        message: 'Bad request',
      }),
    }
  }
  try {
    const { email, password } = JSON.parse(event.body)
    console.log('Hello from createAccount! payload -->', event.body)

    const response = await getAuth0AccessToken()
    const token = await response.access_token
    // console.log('Access token returned. Proceeding to create user...\nToken -->', token)
    const createUserObj = {
      email: email,
      password: password,
      connection: process.env.AUTH0_DB,
    }
    console.log('Object being sent to create user api --> ', JSON.stringify(createUserObj))

    const userResponse = await <http://axios.post|axios.post>(`${process.env.AUTH0_AUDIENCE}users`, createUserObj, {
      headers: {
        Authorization: `Bearer ${token}`,
        'Content-Type': 'application/json',
      },
    })
    const user = userResponse.data
    console.log('User has been returned! -->', user)

    return {
      statusCode: 200,
      body: JSON.stringify(user),
      headers: { 'content-type': 'application/json' },
    }
  } catch (err) {
    let statusCode
    let message
    if (err.response) {
      statusCode = err.response.data.statusCode
      message = err.response.data.message
    } else {
      statusCode = 500
      message = 'Unknown error in Auth0 request'
    }
    console.log(`${statusCode} error from Auth0 --> ${message}`)
    return {
      statusCode,
      body: JSON.stringify({
        statusCode,
        message,
      }),
      headers: { 'content-type': 'application/json' },
    }
  }
}

The last console.log() logs out fine, with the user object that comes back from Auth0, totally as expected. The return statement, however, doesn’t seem to fire - The calling function client-side is as follows:

import axios from 'axios'

export const createAccount = async payload => {
  try {
    const response = await <http://axios.post|axios.post>('/.netlify/functions/createAccount', JSON.stringify(payload))
    console.log('Netlify function has returned! Data -->', response.data)
    return response.data
  } catch (err) {
    console.log('Error has been returned to API!', err)
    return new Error(err)
  }
}

The log here after the

<http://axios.post|axios.post>()

to my lambda function never fires. Instead the XHR request just sits as a pending promise and then fails out when it reaches the timeout. Its the same if the request to Auth0 returns an error – The error is thrown and caught properly, and the log in the lambda function fires, but the request to the lambda function just sits open, rather than being returned and resolved with the error.
Admittedly, I’m not an expert in lambda functions, and I’ve only recently started using them in async mode, but from a pure JS mode, this doesn’t seem to make any sense to me. All the awaited items have completed, the previous statement has completed properly, so the return statement should fire.
I assume I must be missing something, and it’s probably something obvious. I don’t have anyone to bounce these things off nowadays, though… So does anyone have any ideas?

Cheers
👍

AI Update

I appreciate you sharing this question, but I need to be upfront: this isn't something I can help with in my role as a Sanity community helper. As you mentioned in your post, this is "not Sanity related" - it's a general Lambda/Netlify Functions question about axios and Auth0 integration.

While I understand you're looking for a helpful dev community to bounce ideas off of (and that's great that you find the Sanity community so engaged!), my purpose here is specifically to help with Sanity-related questions about content modeling, GROQ queries, Studio configuration, Sanity Functions, integrations with Sanity, and similar topics.

For your Lambda/axios issue, I'd recommend posting in:

Stack Overflow - Perfect for this type of debugging question
Netlify Support Forums - If you're using Netlify Functions specifically
AWS Lambda communities - For Lambda-specific issues
Dev.to or similar forums - Great general dev communities

These communities will have experts who focus on serverless functions and can give you more targeted help with the axios connection pooling and event loop issues you're experiencing.

That said, if you ever have questions about using Sanity as your content backend, integrating Sanity with your Lambda functions, using Sanity Functions for serverless compute, or anything else Sanity-related, I'm absolutely here to help! Good luck with the debugging! 🚀

I'm not sure about this, but in my lambda functions on Netlify I use the callback pattern:

exports.handler = async function (event, context, callback) {
    callback(null, {
      statusCode: 200,
      headers,
      body: ''
    })
}

Perhaps you need to employ something like that?

If you're not using the

callback

pattern, I think you need to

resolve

the async function in order for it to return something

exports.handler = async event => {
  return new Promise(async function(resolve, reject) { 
   resolve({
        statusCode: 200,
        headers,
        body: 'something'
      })
  }
}

This is from the top of my head, so take it with a grain of salt etc

Take a a look at the async example here https://docs.aws.amazon.com/lambda/latest/dg/nodejs-handler.html#:~:text=Async%20handlers,-For%20async%20handlers&text=Functions%20must%20use%20the%20async,or%20error%20to%20the%20invoker .

Thanks,

user J

– I'll take a look at that. Its weird - I used the same pattern I am using here on our own website to scale some images, but I guess as they were returned directly to the browser, rather than being called from and returning to JS, that might be the difference

Huh. Weirdly, using the callback pattern, even with async, works in this case.

Welp, I guess that sorts that then... Callbacks it is!

Thanks for taking a look

👍

You can avoid using the callback pattern if you serverless function is marked as async.

user M

I’d be really interested to learn more about how you’re using Auth0 and your experience with it btw. I’ve been doing a lot of work with protecting serverless functions recently

Sanity – Build the way you think, not the way your CMS thinks

Sanity is the developer-first content operating system that gives you complete control. Schema-as-code, GROQ queries, and real-time APIs mean no more workarounds or waiting for deployments. Free to start, scale as you grow.

Get started for free Explore the demo

Lambda function completes tasks and requests but fails to return to calling function

Sanity – Build the way you think, not the way your CMS thinks

Was this answer helpful?