Added RDS Aurora MySQL blue/green deployment resource and test (testing WIP)

[autotune]

Description

resource "aws_rds_cluster" "default" {
  cluster_identifier = "aurora-cluster-demo-3"
  availability_zones = ["us-east-1b", "us-east-1c", "us-east-1d"]
  database_name      = "mydb"
  master_username    = "foo"
  master_password    = "barbut8chars"
  engine             = "aurora-mysql"
  engine_version     = "5.7.mysql_aurora.2.12.0"
  skip_final_snapshot = true 
  db_cluster_parameter_group_name = "blue57"
}

resource "aws_rds_cluster_instance" "cluster_instances" {
  depends_on         = [aws_rds_cluster.default]
  count              =  2 
  identifier         = "aurora-cluster-${count.index}"
  cluster_identifier = "aurora-cluster-demo-3" 
  engine             = aws_rds_cluster.default.engine
  engine_version     = aws_rds_cluster.default.engine_version
  instance_class     = "db.t3.small"
  db_parameter_group_name = "blue57instance"
}

resource "aws_rds_cluster_blue_green_deployment" "status" {
  cluster_identifier = aws_rds_cluster.default.cluster_identifier
  cleanup_resources = true 
  engine = aws_rds_cluster.default.engine
  switchover_enabled = var.switchover_enabled 
  create_deployment = var.create_deployment
}

Relations

Closes #0000
--->

Closes #28956

Output from Acceptance Testing

WIP

% make testacc TESTS=TestAccXXX PKG=ec2

...

[github-actions]

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[autotune]

@justinretzolk I have not been able to build a test for this as the parameter group is unable to wait for Aurora DB instance creation. Going to submit what I've finished so far today, if someone else wants to take over and finish building out the test portion that is fine with me.

[timclifford]

internal/service/rds/cluster_blue_green_resource.go:979:7: syntax error: unexpected comma at end of statement

[timclifford]

internal/service/rds/cluster_blue_green_resource.go:983:3: syntax error: unexpected ( after top level declaration

[bdeetz]

Hey @autotune,
In this section of code, there is some funky bracing and indentation issues preventing us from getting past linting to build. I'm trying to debug this issue, but when I fix the braces and indentation I find references to variables that don't exist. Can you fill us in on what you think is going on in this code block?

[gdavison]

Thanks for the work you've put into this, @autotune. Unfortunately, a stand-alone resource for RDS Blue/Green Deployments does not fit with the Terraform model of declarative infrastructure: Using the resource would require multiple iterations of editing the Terraform configuration, applying the configuration, or importing resources. A separate tool that can manage the orchestration steps would be a better fit.

Blue/Green Deployments work with aws_db_instance because it is a single self-contained resource, whereas an Aurora cluster is made up of one aws_rds_cluster and at least one aws_rds_cluster_instance.

For more details, see #34551

[github-actions]

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