AWS Lambda & API Gateway - 500 from browser but not from curl

Question

I'm struggling with AWS Lambda and API Gateway. I can call my API fine from curl and Postman, but not from my browser.

This works

curl --header "Content-Type: application/json" \
     --request POST \
     --data '{ "baseId" : "app0ZJgZxm6LC8rBB", "tableName": "Stories", "action": "select" }' \
     'https://gpzy1rrcwg.execute-api.us-east-1.amazonaws.com/Prod/'

This does NOT work (link to run it on CodePen)

<!DOCTYPE html>
<html>
<head>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script>
$(document).ready(function(){
    $("button").click(function(){
        $.ajax({
            type: 'POST',
            url: 'https://gpzy1rrcwg.execute-api.us-east-1.amazonaws.com/Prod/',
            dataType: 'json',
            contentType: 'application/json',
            data: JSON.stringify({
                "baseId" : "app0ZJgZxm6LC8rBB",
                "tableName": "Stories",
                "action": "select"
            }),
            success: function (response) {
                console.log(response)
                alert('it worked')
            },
            error: function (err) {
                console.log(err)
                alert('it failed')
            }
        });
    });
});
</script>
</head>
<body>

<button>Test</button>

</body>
</html>

link to run it on CodePen

Can you get logs from your lambda, or configure it to return exceptions and stack traces in the response? Can you check the request body in your browser's network tools to make sure it's the same as the curl body? — Rup
– Rup, Commented Aug 28, 2018 at 17:15
Actually this might be a CORS issue. Have you set up your Lambda for CORS? — Rup
– Rup, Commented Aug 28, 2018 at 17:17

Pedro Henrique · Accepted Answer · 2018-08-28 18:08:12Z

4

It is probably a CORS problem, as @Rup said in the comments. From the JQuery documentation on the contentType option for .ajax() you see this:

For cross-domain requests, setting the content type to anything other than application/x-www-form-urlencoded, multipart/form-data, or text/plain will trigger the browser to send a preflight OPTIONS request to the server

By checking the network tab on your browser you will see it is sending an OPTION request. In fact, by simply removing the contentType parameter your code will run as expected.

answered Aug 28, 2018 at 18:08

Pedro Henrique

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Comments

trnrao · Accepted Answer · 2018-08-29 08:39:27Z

0

What is the Integration Mode between API gateway and Lambda - Is it Proxy based or the earlier one.?

Have you enabled CORS in your API Gateway Method.? https://docs.aws.amazon.com/apigateway/latest/developerguide/how-to-cors.html

answered Aug 29, 2018 at 8:39

trnrao

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