Netlify Lambda Functions

Question

I am having an issue getting a 502 error back when I call my Netlify function. Is there something I am doing wrong in my Axios call or does the "error" sent in the callback need to be an actual Error object?

Below is the example of my function:

const axios = require('axios')
require('dotenv').config()
const https = require('https')
const headers = {
  'Access-Control-Allow-Origin': '*',
  'Access-Control-Allow-Headers': 'Content-Type'
}

exports.handler = function (event, context, callback) {
  // your server-side functionality

  axios
    .post(
      `https://us18.api.mailchimp.com/3.0/lists/${
        process.env.LIST_ID
      }/members/`, {
        email_address: '[email protected]',
        status: 'subscribed'
      }, {
        auth: {
          username: 'admin',
          password: process.env.MAILCHIMP_API_KEY
        }
      }
    )
    .then(response => {
      callback(null, {
        statusCode: 200,
        headers,
        body: response.data
      })
    })
    .catch(err => {
      callback(JSON.stringify(err.response.data))
    })
}

talves · Accepted Answer · 2018-08-03 16:43:27Z

2

Netlify announced in April (2018) that Node.js 8.10 would be the default in Netlify functions.

Using Callback Parameter:

When you need to return an error in Lambda functions on Netlify using the Callback Parameter, it will be the same format as the Lambda functions for AWS.

You will need to return an Error in the first parameter of the callback as you can see in the AWS documentation

callback(Error error, Object result);

The error is used if not null and the result will be ignored.

Using Async Handler:

You also have the option to return your error in the response with an error status code like the example function below.

import fetch from "node-fetch";

const API_ENDPOINT =
  "https://08ad1pao69.execute-api.us-east-1.amazonaws.com/dev/random_joke";

exports.handler = async (event, context) => {
  return fetch(API_ENDPOINT)
    .then(response => response.json())
    .then(data => ({
      statusCode: 200,
      body: `${data.setup} ${data.punchline} *BA DUM TSSS*`
    }))
    .catch(error => ({ statusCode: 422, body: String(error) }));
};

Showing simple tests

Error

exports.handler = function(event, context, callback) {
  const err = new Error("this is an error")
  callback(err);
}

Response (response status code 502):

{"errorMessage":"this is an error","errorType":"Error","stackTrace":["48.exports.handler (/var/task/showerror.js:75:13)"]}

Object

exports.handler = function(event, context, callback) {
  const err = {statusCode: 422, body: "this is an error"}
  callback(err);
}

Response (response status code 502):

{"errorMessage":"[object Object]"}

String

exports.handler = function(event, context, callback) {
  const err = "this is an error"
  callback(err);
}

Response (response status code 502):

{"errorMessage":"this is an error"}

NOTE:

If you want to use callback and have the error status code in the response, you would just pass it in an object to the response.

exports.handler = function(event, context, callback) {
  const err = {statusCode: 422, body: "this is an error"}
  callback(null, err);
}

Response (response status code 422):

this is an error

edited Aug 3, 2018 at 16:43

answered Aug 2, 2018 at 23:36

talves

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3 Comments

MontyTheMack Over a year ago

So it can’t just be any ol object returned? It HAS to be an Error object? If I’m understanding correctly?

talves Over a year ago

I have not tested any object, but from the docs it just passes the error (first parameter) to be populated to the response when using the callback function.

talves Over a year ago

I did the tests in a Netlify Function for callback using Error,Object, and String and added it to the answer. I also included the passing of the result instead, so you can see how it returns the status code given.

Chad Elias · Accepted Answer · 2018-08-03 05:04:44Z

1

You could arrange the response like so:

var response = {
    statusCode: 4xx
    body: ''
}

and then pass it to the callback to return the error

response.body = 'some error text here';
callback(response);

They are using AWS Lambda, so if you can do it in the console you should in theory be able to call things the same way since they are taking your code and deploying it via Cloudformation in their infrastructure.

answered Aug 3, 2018 at 5:04

Chad Elias

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Netlify Lambda Functions

2 Answers 2

Using Callback Parameter:

Using Async Handler:

Showing simple tests

Error

Object

String

NOTE:

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Collectives™ on Stack Overflow

2 Answers 2

Using Callback Parameter:

Using Async Handler:

Showing simple tests

Error

Object

String

NOTE:

3 Comments

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