CODEWITHSUNDEEP
python-3.xamazon-web-servicesapirest
Xbert
Xbert

Reputation: 91

Lambda execution failed with status 200 due to customer function error

I'm creating a simple Lambda function to serve a POST in AWS Gateway:

import json
import boto3
from datetime import datetime


def lambda_handler(event,context):
    wf = event['WF']
    
    if wf == 'start1':
            body = 'Suceeded'
            return {
                "isBase64Encoded": False,
                'statusCode': 200,
                'body': json.dumps(body),
                'headers': {
                'Content-Type': 'application/json'
                    }   
                }
    else:
            body = 'Failed'
            return {
                "isBase64Encoded": False,
                'statusCode': 400,
                'body': json.dumps(body),
                'headers': {
                'Content-Type': 'application/json'
                    }   
             }

If I send a POST with this body is successful:

{
  "WF": "start1",
  "Context": "OK"
}

Returns:

Test Event Name
test

Response
{
  "isBase64Encoded": false,
  "statusCode": 200,
  "body": "\"Suceeded\"",
  "headers": {
    "Content-Type": "application/json"
  }
}

Function Logs
START RequestId: 91663a9d-d8b6-4aad-b8b6-eb2f15ff0354 Version: $LATEST
END RequestId: 91663a9d-d8b6-4aad-b8b6-eb2f15ff0354
REPORT RequestId: 91663a9d-d8b6-4aad-b8b6-eb2f15ff0354  Duration: 1.74 ms   Billed Duration: 2 ms   Memory Size: 128 MB Max Memory Used: 66 MB  Init Duration: 300.73 ms

Request ID
91663a9d-d8b6-4aad-b8b6-eb2f15ff0354

But if I run a test in the API Gateway service in AWS I get:

Fri Jun 04 13:45:22 UTC 2021 : Sending request to https://XXXXXXX
Fri Jun 04 13:45:22 UTC 2021 : Received response. Status: 200, Integration latency: 15 ms
Fri Jun 04 13:45:22 UTC 2021 : Endpoint response headers: {Date=Fri, 04 Jun 2021 13:45:22 GMT, Content-Type=application/json, Content-Length=159, Connection=keep-alive, x-amzn-RequestId=d479fdac-6737-42fa-96a3-9e991056b48d, X-Amz-Function-Error=Unhandled, x-amzn-Remapped-Content-Length=0, X-Amz-Executed-Version=$LATEST, X-Amzn-Trace-Id=root=1-60ba2e72-ff62f051febbd21d6cc9d114;sampled=0}
Fri Jun 04 13:45:22 UTC 2021 : Endpoint response body before transformations: {"errorMessage": "'WF'", "errorType": "KeyError", "stackTrace": ["  File \"/var/task/lambda_function.py\", line 7, in lambda_handler\n    wf = event['WF']\n"]}
Fri Jun 04 13:45:22 UTC 2021 : Lambda execution failed with status 200 due to customer function error: 'WF'. Lambda request id: d479fdac-6737-42fa-96a3-9e991056b48d
Fri Jun 04 13:45:22 UTC 2021 : Method completed with status: 502

Why line 7 is wrong? Is there another way to parse the body of the POST?

Upvotes: 5

Views: 16523

Answers (3)

mel3kings
mel3kings

Reputation: 9415

In my instance, I had received this error when invoking my Lambda function via API gateway, it was also completely fine when invoking directly the lambda function expecting a simple JSON body.

my expected payload: {"Email": "[email protected]"}

It turns out Lambda Proxy Integration in the POST in the configuration API gateway changes the payload structure before passing into Lambda, and I was getting the error missing Key attribute Email. I noticed that line Endpoint request body after transformations: in cloudwatch. I learned that it was changing the payload.

How I debug this:

Upvotes: 0

Xbert
Xbert

Reputation: 91

The solution was found by disabling Lambda Proxy Integration in the POST - Integration Request.

Upvotes: 3

Tom Nijs
Tom Nijs

Reputation: 3962

It looks like your API Gateway invocation is not populating the event parameter of your Lambda function. When you create a test event your lambda function's page, you get to create your own test event. API Gateway will not use this test event, it will instead send an empty event (probably null).

I.e.


import json
import boto3
from datetime import datetime


def lambda_handler(event,context): # Event is null here
    wf = event['WF'] # Attempting to read the attribute 'WF' of null results in an error

Upvotes: 1

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