Bug: event_source decorator with APIGatewayProxyEventV2 causes TypeError in debug mode

[sthuber90]

Expected Behaviour

Using the event source decorator with APIGatewayProxyEventV2 will run Lambda function and not fail with TypeError

Current Behaviour

When activating debug mode through either APIGatewayHttpResolver(debug=True) or POWERTOOLS_EVENT_HANDLER_DEBUG=true causes TypeError: Object of type APIGatewayProxyEventV2 is not JSON serializable and no further debug entries get logged.

Code snippet

from aws_lambda_powertools.utilities.data_classes import (
    APIGatewayProxyEventV2,
    event_source,
)
from aws_lambda_powertools.logging import correlation_paths
from aws_lambda_powertools import Logger
from aws_lambda_powertools.event_handler import APIGatewayHttpResolver
from aws_lambda_powertools.utilities.typing import LambdaContext

logger = Logger()
app = APIGatewayHttpResolver(debug=True)


@logger.inject_lambda_context(correlation_id_path=correlation_paths.API_GATEWAY_HTTP)
@event_source(data_class=APIGatewayProxyEventV2)
def lambda_handler(event: APIGatewayProxyEventV2, context: LambdaContext):
    return app.resolve(event, context)

@app.get("/my/path")
def get_hello_universe():
    return {"message": "hello universe"}

Possible Solution

Workaround: Enable debug mode and comment event source out

Steps to Reproduce

Create a Lambda function accepting APIGatewayProxyEventV2 requests. Decorate the handler method with logger inject and event source and add a simple route that will just return a small JSON response. Then enable debug mode by one of the supported ways and watch the lambda function fail

AWS Lambda Powertools for Python version

latest (Layer version 18)

AWS Lambda function runtime

3.9

Packaging format used

Lambda Layers

Debugging logs

[ERROR] TypeError: Object of type APIGatewayProxyEventV2 is not JSON serializable
Traceback (most recent call last):
  File "/opt/python/aws_lambda_powertools/logging/logger.py", line 354, in decorate
    return lambda_handler(event, context)
  File "/opt/python/aws_lambda_powertools/middleware_factory/factory.py", line 134, in wrapper
    response = middleware()
  File "/opt/python/aws_lambda_powertools/utilities/data_classes/event_source.py", line 39, in event_source
    return handler(data_class(event), context)
  File "/var/task/app.py", line 28, in lambda_handler
    return app.resolve(event, context)
  File "/opt/python/aws_lambda_powertools/event_handler/api_gateway.py", line 495, in resolve
    print(self._json_dump(event), end="")
  File "/opt/python/aws_lambda_powertools/event_handler/api_gateway.py", line 688, in _json_dump
    return self._serializer(obj)
  File "/var/lang/lib/python3.9/json/__init__.py", line 234, in dumps
    return cls(
  File "/var/lang/lib/python3.9/json/encoder.py", line 199, in encode
    chunks = self.iterencode(o, _one_shot=True)
  File "/var/lang/lib/python3.9/json/encoder.py", line 257, in iterencode
    return _iterencode(o, 0)
  File "/opt/python/aws_lambda_powertools/shared/json_encoder.py", line 16, in default
    return super().default(obj)
  File "/var/lang/lib/python3.9/json/encoder.py", line 179, in default
    raise TypeError(f'Object of type {o.__class__.__name__} '

[heitorlessa]

Hey @sthuber90 tha is for reporting it - we'll look into it as soon as we can.

Any particular reason you're using event_source with Event Handler?

We already do that for you upon a Lambda invocation, and make it available under app.current_event property.

https://awslabs.github.io/aws-lambda-powertools-python/latest/core/event_handler/api_gateway/#accessing-request-details

Thanks!!

[sthuber90]

Thank you. No, no particular reason combining @event_source and APIGatewayHttpResolver. It's perfectly fine for me to remove the event source decorator. Are the resolver and event source incompatible? If so, I didn't see it in the docs

[heitorlessa]

Ah great, I was mostly curious if you knew. For the decorator, I need to double check in the custom serializer part but IIRC it should work, as we reuse it elsewhere.

…

On Mon, 25 Apr 2022 at 19:30, Stephan ***@***.***> wrote: Thank you. No, no particular reason combining @event_source and APIGatewayHttpResolver. It's perfectly fine for me to remove the event source decorator. Are the resolver and event source incompatible? If so, I didn't see it in the docs — Reply to this email directly, view it on GitHub <#1152 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAZPQBDJ3ZAIEHHNN2MFAO3VG3JC5ANCNFSM5UJG3LXA> . You are receiving this because you commented.Message ID: ***@***.***>

[michaelbrewer]

@heitorlessa @sthuber90 - i am sorry for missing this edge case, but it is pretty valid if your handler wants to use the data class. So i put up a PR which is pretty small.

Otherwise a current workaround would be:

@logger.inject_lambda_context(correlation_id_path=correlation_paths.API_GATEWAY_HTTP)
@event_source(data_class=APIGatewayProxyEventV2)
def lambda_handler(event: APIGatewayProxyEventV2, context: LambdaContext):
    return app.resolve(event.raw_event, context)

One thing i notices is that PyCharm does infer that event should be a dict.

[heitorlessa]

thanks @michaelbrewer for the quick fix. I've pushed a change before merging so customers receive a warning that this is not necessary (double serialization), and link to this issue.