Terraform-provider-aws: Add support for RDS Storage auto scaling

[edhgoose]

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Description

AWS have announced auto scaling of storage for some RDS instance types.

https://aws.amazon.com/about-aws/whats-new/2019/06/rds-storage-auto-scaling/

New or Affected Resource(s)

• aws_rds

Potential Terraform Configuration

References

https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/USER_PIOPS.StorageTypes.html#USER_PIOPS.Autoscaling

[ewbankkit]

Requires:

• https://github.com/terraform-providers/terraform-provider-aws/pull/9072

[mwarkentin]

I'm curious how this will look like on plans if the AWS storage has diverged from your initial defined storage for the RDS instance?

[bflad]

@mwarkentin presumably Terraform will show a difference for the argument unless ignore_changes is used, e.g.

resource "aws_db_instance" "example" {
  allocated_storage = 123

  # ... other configuration ...

  # Prevent RDS storage auto scaling from recreating the resource
  lifecycle {
    ignore_changes = ["allocated_storage"]
  }
}

When this feature is implemented, we will likely want to add this to the resource documentation.

[bflad]

Speaking of implementation, I don't mind picking this one up right now since no one has yet. 😄

[bflad]

It looks like this will be a new max_allocated_storage argument, where storage autoscaling is enabled if it is configured:

resource "aws_db_instance" "example" {
  allocated_storage     = 100
  max_allocated_storage = 200

  # ... other configuration ...
}

Given this implementation, we might be able to ignore the allocated_storage argument differences automatically within the resource if max_allocated_storage is defined.

[mwarkentin]

Ah nice, I think that makes sense.

[bflad]

Pull request submitted: #9087

[bflad]

Support for the new max_allocated_storage argument has been merged and will release with version 2.17.0 of the Terraform AWS Provider, likely later today. 👍

[bflad]

This has been released in version 2.17.0 of the Terraform AWS provider. Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading.

For further feature requests or bug reports with this functionality, please create a new GitHub issue following the template for triage. Thanks!

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