(ec2): Update default AmazonLinuxImage to use AMAZON_LINUX_2

Breaking Change feature/request.

The ec2.AmazonLinuxImage defaults to using the latest Amazon Linux image which reached end-of-life at the end of 2020. I’d suggest updating the default image to ec2.AmazonLinuxGeneration.AMAZON_LINUX_2

Environment

• CDK CLI Version: 1.90.0 (build 7edba31)
• Module Version: 1.90.1
• Node.js Version: v15.9.0
• OS: macOS Big Sur 11.2.1
• Language (Version): typescript 4.1.5

[nija-at]

The feature flag mechanism is a good way to achieve this. Adding it to the FEATURE_FLAGS_EXPIRED list on the v2-main branch is the way to go. I’ve captured this here - https://github.com/aws/aws-cdk/blob/master/CONTRIBUTING.md#cdkv2.

The only diff between the two branches would be the docs where the the @default is documented differently.

Anything else we should consider @rix0rrr ?

[rix0rrr]

That sounds like a plan. If we’re going to make this change though, it can’t be in a mad PR dash just before v2 gets released.

The way to do that in a controlled fashion is to add a feature flag which flips the default. We can then change the flag’s default value for v2.

We also need @nija-at in here for a good discussion on how these kinds of defaults changes can be seamlessly merged into v2.