From 56106b98cdc2d5cf358104c23a1e2dcf11d83ad6 Mon Sep 17 00:00:00 2001
From: Nikola Midic <nikola.midic@iongroup.com>
Date: Mon, 30 May 2022 13:44:11 +0100
Subject: [PATCH] Ability to specify different instance type for replicas

---
 README.md    | 5 +++--
 main.tf      | 2 +-
 variables.tf | 6 ++++++
 3 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/README.md b/README.md
index 1fc0a07..1da192f 100644
--- a/README.md
+++ b/README.md
@@ -180,8 +180,9 @@ resource "aws_rds_cluster_parameter_group" "aurora_cluster_postgres96_parameter_
 | envname | Environment name (eg,test, stage or prod) | string | - | yes |
 | envtype | Environment type (eg,prod or nonprod) | string | - | yes |
 | final_snapshot_identifier | The name to use when creating a final snapshot on cluster destroy, appends a random 8 digits to name to ensure it's unique too. | string | `final` | no |
-| identifier_prefix | Prefix for cluster and instance identifier | string | `` | no |
+| identifier_prefix | Prefix for cluster and instance identifier | string | `""` | no |
 | instance_type | Instance type to use | string | `db.t2.small` | no |
+| replica_instance_type | Instance type to use for replicas | string | `"" (inherits instance_type)` | no |
 | monitoring_interval | The interval (seconds) between points when Enhanced Monitoring metrics are collected | string | `0` | no |
 | name | Name given to DB subnet group | string | - | yes |
 | password | Master DB password | string | - | yes |
@@ -199,7 +200,7 @@ resource "aws_rds_cluster_parameter_group" "aurora_cluster_postgres96_parameter_
 | replica_scale_out_cooldown | Cooldown in seconds before allowing further scaling operations after a scale out | string | `300` | no |
 | security_groups | VPC Security Group IDs | list | - | yes |
 | skip_final_snapshot | Should a final snapshot be created on cluster destroy | string | `false` | no |
-| snapshot_identifier | DB snapshot to create this database from | string | `` | no |
+| snapshot_identifier | DB snapshot to create this database from | string | `""` | no |
 | storage_encrypted | Specifies whether the underlying storage layer should be encrypted | string | `true` | no |
 | subnets | List of subnet IDs to use | list | - | yes |
 | username | Master DB username | string | `root` | no |
diff --git a/main.tf b/main.tf
index 2dc3638..fb5284e 100644
--- a/main.tf
+++ b/main.tf
@@ -204,7 +204,7 @@ resource "aws_rds_cluster_instance" "cluster_instance_n" {
   engine_version               = var.engine-version
   identifier                   = var.identifier_prefix != "" ? format("%s-node-%d", var.identifier_prefix, count.index + 1) : format("%s-aurora-node-%d", var.envname, count.index + 1)
   cluster_identifier           = aws_rds_cluster.default.id
-  instance_class               = var.instance_type
+  instance_class               = var.replica_instance_type != "" ? var.replica_instance_type : var.instance_type
   publicly_accessible          = var.publicly_accessible
   db_subnet_group_name         = aws_db_subnet_group.main.name
   db_parameter_group_name      = var.db_parameter_group_name
diff --git a/variables.tf b/variables.tf
index 9d2f77f..ce0ecaf 100644
--- a/variables.tf
+++ b/variables.tf
@@ -46,6 +46,12 @@ variable "instance_type" {
   description = "Instance type to use"
 }
 
+variable "replica_instance_type" {
+  type        = string
+  default     = ""
+  description = "Instance type to use for replicas. Inherits instance_type value if unspecified."
+}
+
 variable "publicly_accessible" {
   type        = string
   default     = "false"