[Breaking Changes] Use Launch Template

[michaelaw320]

Description

Convert Autoscaling Group to use Launch Template instead of Launch Configuration

Fixes #54 #81
and possibly fixes #44

This is backport from https://github.com/HENNGE/terraform-aws-autoscaling-mixed-instances . The said repository must use Launch Template to support mixed instance policy, so I decided to why not I backport the changes I made as I see more than 1 issue here requesting to use Launch Template with normal Autoscaling Group.

This will introduce breaking changes on input variables:

• create_lc is changed to create_lt
• launch_configuration changed to launch_template
• parameters which has lc is changed to lt (naming sense)
• root_block_device, ebs_block_device, ephemeral_block_device changed to block_device_mappings

This PR tries to keep the behaviour the same (except for few inevitable changes above) and keep the changes minimal. Also this PR has not added features that becomes possible when using Launch Template (advanced network configurations, spot market configurations, etc.)

Currently I have no intention of supporting both Launch Configuration and Launch Template in the same module, it will make it complicated, and I see Launch Template supersedes Launch Configuration features, if there's anyone who is willing to support both, please close this PR and go with that PR instead 🙇

[acsrujan]

Should we support launch template versions and setting a version as default in this PR?

[jwhitcraft]

ping @antonbabenko can we get a review on this?

[bryantbiggs]

thanks @michaelaw320 for the PR! I don't know if we can proceed with just replacing the launch config with the launch template as this module is widely used in the launch config version. I think we have two possible routes (in my opinion):

1. Updating the module to provide the option to use either launch config OR launch template. This would be quite an undertaking and should in theory support using the launch config as the default
2. Create a second module for autoscaling group that uses the launch template

Personally, I am more in favor of item 1 but it will take some work and a bit of testing to get it right. Thoughts? Feedback?

[yogeek]

@bryantbiggs Seems to me that option 1 is more flexible indeed and would allow a smoother transition for legacy code to go towards launch_template.
Is there any current work on this or is it currently paused ?
Thanks

[dawidmalina]

Having this will allow us to use gp3 - looks like launch configuration is not (yet) supported: hashicorp/terraform-provider-aws#16514

[github-actions]

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