Why is my AWS Lambda function ending before finishing with no timeout message?

Question

I've been using AWS Lambda and testing with SAM local for nearly a year with no major issues. However, I've written a Lambda function which modifies some files with the S3 API.

The function ends with a 502: Invalid lambda response received: Lambda returned <class 'NoneType'> instead of dict

This is before my function has had a chance to finish... I've managed to condense the code to the following:

exports.handler = async (event, context) => {
    console.log("Goldi");
    await fish(event, context);
    console.log("Locks");
    return { statusCode: 200, body: "Finished!" };
};

No matter whether I run this in SAM Local or upload to AWS Lambda, I get this output:

START RequestId: 6a30e157-3e9b-465e-a945-3e9f7fa2cd7e Version: $LATEST
2022-01-12T18:36:27.601Z        6a30e157-3e9b-465e-a945-3e9f7fa2cd7e    INFO    Goldi
2022-01-12T18:36:27.603Z        6a30e157-3e9b-465e-a945-3e9f7fa2cd7e    INFO    Some output from fish()...
END RequestId: 6a30e157-3e9b-465e-a945-3e9f7fa2cd7e
REPORT RequestId: 6a30e157-3e9b-465e-a945-3e9f7fa2cd7e  Init Duration: 0.18 ms  Duration: 12600.03 ms   Billed Duration: 12700 ms       Memory Size: 512 MB     Max Memory Used: 512 MB
Invalid lambda response received: Lambda returned <class 'NoneType'> instead of dict
2022-01-12 18:36:38 127.0.0.1 - - [12/Jan/2022 18:36:38] "POST / HTTP/1.1" 502 -

I've configured this Lambda function to have a timeout of several minutes and I do not call any functions in 'context'

I've sunk several hours into trying to figure out how a Lambda function can end without any error message (from my code) or a timeout notice.

Is this a known behaviour? Does anyone know how I can find out what causes the function to suddenly stop with no output?

Is `fish()` actually declared as async? What does it return? — jarmod, Jan 12 '22 at 20:27
`fish()` returns simply an object of: `{ statusCode: 200 };` however the code doesn't even run to the return statement, the Lambda function ends before `fish()` can finish. — TRONJon, Jan 13 '22 at 10:23
It's worth adding the code for `fish()`, at least the minimum that still repros the problem, so that someone here can potentially test with it. — jarmod, Jan 13 '22 at 12:15
BTW your logs show a runtime of 12 seconds, so it seems unlikely that the `fish()` function simply returns object of: `{ statusCode: 200 }`. It's doing a lot more work. Does it have exception handling code that logs errors? — jarmod, Jan 13 '22 at 13:23

score 2 · Answer 1 · answered Nov 28 '22 at 19:14

2

Add async to the function definition to fix an issue

 module.exports.default = async () => {
  return {
    statusCode: 200,
  };
};

answered Nov 28 '22 at 19:14

Andrii Melashchenko

41
4

score 1 · Answer 2 · answered Jan 12 '22 at 18:54

1

What is the memory size configuration if the timeout is correct it might be the memory that is hampering the performance

answered Jan 12 '22 at 18:54

priyanshu kumar

76
1
6

I've increased the memory limit from 512 to 4096, and the issue still remains. When monitoring the performance on my computer, this lambda function isn't using much memory at all. – TRONJon Jan 12 '22 at 19:30

score 0 · Answer 3 · answered Jan 13 '22 at 10:58

It possible when lambda abruptly exits in one of the code path. Something in lines of System.exit() in Java.

In JS, the lambda are run on loop to consume the event. If your fish function closes the lambda environment by maybe calling end of runtime / closing the socket on which the response is supposed to be sent. Lambda will finish there itself without sending response or timeout.

req.on('socket', function (socket) { socket.unref() })

score 0 · Answer 4 · answered Apr 30 '22 at 10:35

So from the following tutorial covering how to get lambdas and api-gateway working using CDK, I managed to isolate that without the following line will result in the 502 BAD GATEWAY error experienced, with the suggested return type as described. It's in the new apigateway.RestApi props.

defaultCorsPreflightOptions: {
...
        allowOrigins: ['http://localhost:3000'],
      },

The op doesn't specify his infrastructure propositioning method. If not using the CDK and using Cloud Formation YAML then it's probably related to the equivalent in the expanded YAML (although the net result of the expansion is beyond my competency).

method.response.header.Access-Control-Allow-Origin

BrokerAPItest41BB435C:
    Type: AWS::ApiGateway::Resource
    Properties:
      ParentId: !GetAtt 'BrokerAPID825C3CC.RootResourceId'
      PathPart: test
      RestApiId: !Ref 'BrokerAPID825C3CC'
    Metadata:
      aws:cdk:path: BrokerAwsDeployStack/BrokerAPI/Default/test/Resource
  BrokerAPItestOPTIONS843EE5C3:
    Type: AWS::ApiGateway::Method
    Properties:
      HttpMethod: OPTIONS
      ResourceId: !Ref 'BrokerAPItest41BB435C'
      RestApiId: !Ref 'BrokerAPID825C3CC'
      AuthorizationType: NONE
      Integration:
        IntegrationResponses:
          - ResponseParameters:
              method.response.header.Access-Control-Allow-Headers: '''Content-Type,X-Amz-Date,Authorization,X-Api-Key,X-Amz-Security-Token,X-Amz-User-Agent'''
              method.response.header.Access-Control-Allow-Origin: '''http://localhost:3000'''
              method.response.header.Vary: '''Origin'''
              method.response.header.Access-Control-Allow-Methods: '''OPTIONS,GET,PUT,POST,DELETE,PATCH,HEAD'''
            StatusCode: '204'
        RequestTemplates:
          application/json: '{ statusCode: 200 }'
        Type: MOCK
      MethodResponses:
        - ResponseParameters:
            method.response.header.Access-Control-Allow-Headers: true
            method.response.header.Access-Control-Allow-Origin: true
            method.response.header.Vary: true
            method.response.header.Access-Control-Allow-Methods: true
          StatusCode: '204'
    Metadata:

Why is my AWS Lambda function ending before finishing with no timeout message?

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