[S3] add event notification creates BucketNotificationsHandler lambda

[RishiKapadia20]

❓ General Issue

The Question

I am trying to add a event notification to my s3 bucket which will cause a lambda to be invoked, however looking what resources that are created I can see that it's creating a new lambda called BucketNotificationsHandler. I don't understand why this resource is being made. How can I just point my buckets to just trigger an existing lambda without creating random resources?

Code:

        bucket = aws_s3.Bucket(
            self,
            id=self.id,
            bucket_name=self.bucket_name,
            encryption=aws_s3.BucketEncryption.S3_MANAGED
        )

        lambda_function = aws_lambda.Function.from_function_arn(
            self,
            id=lambda_name,
            function_arn=f"arn:aws:lambda:{aws_region}:{aws_account}:function:{lambda_name}"
        )

        lambda_destination = aws_s3_notifications.LambdaDestination(lambda_function)

        bucket.add_event_notification(
            aws_s3.EventType.OBJECT_CREATED,
            lambda_destination,
            aws_s3.NotificationKeyFilter(suffix=suffix_value)
        )

Resources being created:

[+] AWS::S3::Bucket 
[+] Custom::S3BucketNotifications 
[+] AWS::IAM::Role BucketNotificationsHandler050a0587b7544547bf325f094a3db834/Role BucketNotificationsHandler050a0587b7544547bf325f094a3db834RoleB6FB88EC 
[+] AWS::IAM::Policy BucketNotificationsHandler050a0587b7544547bf325f094a3db834/Role/DefaultPolicy BucketNotificationsHandler050a0587b7544547bf325f094a3db834RoleDefaultPolicy2CF63D36 
[+] AWS::Lambda::Function BucketNotificationsHandler050a0587b7544547bf325f094a3db834 BucketNotificationsHandler050a0587b7544547bf325f094a3db8347ECC3691 

Environment

• CDK CLI Version: 1.46.0
• Module Version:
• Node.js Version: v12.6.0
• OS: OSX Mojave
• Language (Version): Python (3.7)

[iliapolo]

Hi @RishiKapadia20

The BucketNotificationsHandler lambda is an internal CDK lambda needed to apply bucket notification configurations.
Have a look at this for some more detail.

We might need some clarifications around this in the docs.

Thanks

[github-actions]

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