chore: correct examples and scenario where replicas are used (#317)

examples/replica-mysql/main.tf

@@ -89,7 +89,8 @@ module "master" {
   port     = local.port
 
   multi_az               = true
-  subnet_ids             = module.vpc.database_subnets
+  create_db_subnet_group = false
+  db_subnet_group_name   = module.vpc.database_subnet_group_name
   vpc_security_group_ids = [module.security_group.this_security_group_id]
 
   maintenance_window              = "Mon:00:00-Mon:03:00"
@@ -101,9 +102,6 @@ module "master" {
   skip_final_snapshot     = true
   deletion_protection     = false
 
-  create_db_option_group    = false
-  create_db_parameter_group = false
-
   tags = local.tags
 }
 
@@ -130,12 +128,11 @@ module "replica" {
   storage_encrypted     = false
 
   # Username and password should not be set for replicas
-  username = ""
-  password = ""
+  username = null
+  password = null
   port     = local.port
 
   multi_az               = false
-  subnet_ids             = module.vpc.database_subnets
   vpc_security_group_ids = [module.security_group.this_security_group_id]
 
   maintenance_window              = "Tue:00:00-Tue:03:00"
@@ -143,13 +140,11 @@ module "replica" {
   enabled_cloudwatch_logs_exports = ["general"]
 
   backup_retention_period = 0
-  final_snapshot_identifier = local.name
+  skip_final_snapshot     = true
   deletion_protection     = false
 
   # Not allowed to specify a subnet group for replicas in the same region
   create_db_subnet_group = false
-  create_db_option_group    = false
-  create_db_parameter_group = false
 
   tags = local.tags
 }

examples/replica-postgres/main.tf

@@ -89,7 +89,8 @@ module "master" {
   port     = local.port
 
   multi_az               = true
-  subnet_ids             = module.vpc.database_subnets
+  create_db_subnet_group = false
+  db_subnet_group_name   = module.vpc.database_subnet_group_name
   vpc_security_group_ids = [module.security_group.this_security_group_id]
 
   maintenance_window              = "Mon:00:00-Mon:03:00"
@@ -127,12 +128,11 @@ module "replica" {
   storage_encrypted     = false
 
   # Username and password should not be set for replicas
-  username = ""
-  password = ""
+  username = null
+  password = null
   port     = local.port
 
   multi_az               = false
-  subnet_ids             = module.vpc.database_subnets
   vpc_security_group_ids = [module.security_group.this_security_group_id]
 
   maintenance_window              = "Tue:00:00-Tue:03:00"

main.tf

 locals {
-  db_subnet_group_name = coalesce(var.db_subnet_group_name, module.db_subnet_group.this_db_subnet_group_id)
+  db_subnet_group_name = var.replicate_source_db != null ? null : coalesce(var.db_subnet_group_name, module.db_subnet_group.this_db_subnet_group_id)
 
   parameter_group_name_id = var.create_db_parameter_group ? module.db_parameter_group.this_db_parameter_group_id : var.parameter_group_name
 

modules/db_instance/main.tf

@@ -60,8 +60,8 @@ resource "aws_db_instance" "this" {
   final_snapshot_identifier = var.skip_final_snapshot ? null : coalesce(var.final_snapshot_identifier, "${var.final_snapshot_identifier_prefix}-${var.identifier}-${random_id.snapshot_identifier[0].hex}")
 
   performance_insights_enabled          = var.performance_insights_enabled
-  performance_insights_retention_period = var.performance_insights_enabled == true ? var.performance_insights_retention_period : null
-  performance_insights_kms_key_id       = var.performance_insights_enabled == true ? var.performance_insights_kms_key_id : null
+  performance_insights_retention_period = var.performance_insights_enabled ? var.performance_insights_retention_period : null
+  performance_insights_kms_key_id       = var.performance_insights_enabled ? var.performance_insights_kms_key_id : null
 
   replicate_source_db     = var.replicate_source_db
   backup_retention_period = var.backup_retention_period