AWS lambda webhook handler

[Bob Lund]

Hi,

I am having trouble implementing a webhook handler in AWS lambda.

I have an Express handler example:

app.post('/webhook', bodyParser.raw({type: 'application/json'}), async (request, response) => {

where the bodyParse extracts the raw JSON into the request.body.

I cannot find how to do this with the AWS lambda interface: exports.lambdaHandler = async (event, context) => {

event.body is empty.

I found this that discusses how to extract the raw payload without bodyParser but it involves access to the raw HTTP stream which AWS doesn't provide access to.

I guess an alternative would be for stripe to send the webhook as stringified JSON but I don't see how to do that.

Any suggestions how to process webhook events in AWS lambda?

Thanks,

Bob Lund

[Remi J.]

Hello,

Accessing the raw body of the request with AWS lambda can be a bit tricky/confusing. My understanding is that you need to configure a "body mapping template" in the API Gateway to map `$input.body` as expected. This is something they document here [1].

I haven't use AWS Lambda myself recently but I have an old example that might be helpful to start though things might have changed since then:

{
  "method": "$context.httpMethod",
  "body": $input.json('$'),
  "rawBody": "$util.escapeJavaScript($input.body).replaceAll("\\'", "'")",
  "headers": {
    #foreach($param in $input.params().header.keySet())
    "$param": "$util.escapeJavaScript($input.params().header.get($param))"
    #if($foreach.hasNext),#end
    #end
  }
}

There's also a similar discussion in a Github issue on stripe-node that was discussed a while ago here [2] with some details too.

I hope this puts you in the right direction!

Best,

Remi

[1] https://docs.aws.amazon.com/apigateway/latest/developerguide/api-gateway-mapping-template-reference.html#input-variable-reference

[2] https://github.com/stripe/stripe-node/issues/356

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[Igor Shmukler]

I have successfully used https://github.com/vendia/serverless-express
a few years ago.

If you were to use "serverless framework," you could describe your
HTTP API function[s] with serverless.yml.