Wrong replica initialization

[fdmota]

Hopefully I will be able to describe the problem correctly.

With a configuration like this
engine = "aurora-mysql" replica_scale_enabled = true replica_scale_max = 2 replica_scale_min = 1
I would expect to get 1 writer instance + 1 reader instance. Instead I only get 1 writer.

If I increase replica_scale_min to 2 replica_scale_min = 1, I get 1 writer + 2 readers.
With the current module, It is not possible to initialize the cluster with 1 writer and 1 reader.

I believe the solution leave here
resource "aws_rds_cluster_instance" "this" { count = var.create_cluster ? (var.replica_scale_enabled ? var.replica_scale_min : var.replica_count) : 0

instead it should be
resource "aws_rds_cluster_instance" "this" { count = var.create_cluster ? (var.replica_scale_enabled ? var.replica_scale_min + 1: var.replica_count) : 0

note, this important to have the cluster initialized with at least 1 reader otherwise the application autoscaler won't work, since it needs at least 1 reader to be present.

[emillbrandt]

The root of the problem is how the replica_scale_min and replica_count are used to create instances and set the autoscaling policy. aws_rds_cluster_instance uses either of those variables to set the total number of instances (writer + readers) but now aws_appautoscaling_target is setting the number of reader instances to one more than desired. The variable names should be changed to reflect that you are setting the number of readers and then your suggested change makes more sense.

[github-actions]

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