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Cannot recreate database instance due to create_before_destroy set to true on the cluster instance #257

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nitrocode opened this issue Mar 14, 2025 · 2 comments · May be fixed by #258
Open

Cannot recreate database instance due to create_before_destroy set to true on the cluster instance #257

nitrocode opened this issue Mar 14, 2025 · 2 comments · May be fixed by #258
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bug 🐛 An issue with the system

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@nitrocode
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nitrocode commented Mar 14, 2025 •
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Describe the Bug

Hi all.

The use-cases where the database has to be recreated from a snapshot, results in an error due to a conflicting name.

I noticed that create_before_destroy = true is on both of these resources

aws_rds_cluster_instance
aws_rds_cluster_parameter_group
aws_db_parameter_group

The second aws_rds_cluster_parameter_group and third aws_db_parameter_group ones correctly has the option to either use name or name_prefix which can avoid the recreation issue, but the first aws_rds_cluster_instance only uses identifier without an option to use identifier_prefix.

terraform-aws-rds-cluster/main.tf

Lines 349 to 351 in d13a56c

resource "aws_rds_cluster_instance" "default" {
count = local.cluster_instance_count
identifier = "${module.rds_identifier[0].id}-${count.index + 1}"

terraform-aws-rds-cluster/main.tf

Lines 404 to 408 in d13a56c

resource "aws_rds_cluster_parameter_group" "default" {
count = local.enabled ? 1 : 0
name_prefix = var.parameter_group_name_prefix_enabled ? "${coalesce(var.rds_cluster_parameter_group_name, module.this.id)}${module.this.delimiter}" : null
name = !var.parameter_group_name_prefix_enabled ? coalesce(var.rds_cluster_parameter_group_name, module.this.id) : null

terraform-aws-rds-cluster/main.tf

Lines 429 to 433 in d13a56c

resource "aws_db_parameter_group" "default" {
count = local.enabled ? 1 : 0
name_prefix = var.parameter_group_name_prefix_enabled ? "${coalesce(var.db_parameter_group_name, module.this.id)}${module.this.delimiter}" : null
name = !var.parameter_group_name_prefix_enabled ? coalesce(var.db_parameter_group_name, module.this.id) : null

Even if the flag identifier_prefix was set to presumably avoid this naming conflict issue, the flag create_before_destroy = true for these resources doesn't make sense to me since if the old database was going to be destroyed, creating a brand new one wouldn't prevent an outage. Is this flag really providing value?

Two ways to solve this and both solutions could also be employed

  • Provide an option to use identifier_prefix for aws_rds_cluster_instance
  • Remove create_before_destroy = true flag for these resources

Expected Behavior

Recreation without naming conflict

Steps to Reproduce

  1. terraform apply an empty database
  2. provide the snapshot identifier arn which will result in a recreation
  3. terraform apply

You should see the error now

Screenshots

N/A

Environment

terraform 1.11.0
module v1.18.0

Additional Context

  • reopen #192 #213
  • Docs regarding the create_before_destroy flag for aws_db_parameter_group and there is no equivalent for aws_rds_cluster_instance but one can predict if there was, it would most likely recommend identifier_prefix.
@nitrocode nitrocode added the bug 🐛 An issue with the system label Mar 14, 2025
@nitrocode
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cc @finchr since you added the flag, what do you think about this use-case ?

@nitrocode nitrocode linked a pull request Mar 14, 2025 that will close this issue
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@finchr
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finchr commented Mar 14, 2025

cc @finchr since you added the flag, what do you think about this use-case ?

I add a comment to the PR asking why we needed a prefix when we're already using a random_pet.

I'm also a little concerned with "provide the snapshot identifier arn which will result in a recreation" but don't see that this was implemented in PR #258

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feat: add identifier prefixes to recreate resources cloudposse/terraform-aws-rds-cluster
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@finchr @nitrocode