CloudFormation is waiting for NetworkInterfaces associated with the Lambda Function to be cleaned up

Question

I have a CloudFormation stack with Lambda function inside a VPC,
When trying to delete the stack, the AWS CloudFormation gets stuck for 25-30 at least,
I get the following message in the events -

CloudFormation is waiting for NetworkInterfaces associated with the Lambda Function to be cleaned up.

It seems to be due to ENIs being attached to the Functions and the SecurityGroups.

From the Console it did not allow me to delete either the ENI forcibly nor the Security Group, to which the ENI is attached,
So do I just have to wait?

I found some questions and blogs which are even 2 years old,
No solution from AWS?
Automations are supposed to be quick, this is proving to be a huge blocker.

Reference -
CloudFormation issue: couldn't delete stack
https://forum.serverless.com/t/very-long-delay-when-doing-sls-remove-of-lambda-in-a-vpc/2535

Answer 1

As you and others have already mentioned, this is a known issue/"feature". When I last spoke about this with someone from AWS, there were no plans of changing this behavior. If time is really of the essence for you, one work-around you can try is this:

1. Update the Lambda resources in CloudFormation with DeletionPolicy set to Retain.

2. Manually (or via script/API) delete the Lambda and associated resources like ENIs

However, I would not recommend against the above mentioned work-around. It is easy to forget something which will leave you with a cluttered environment.