feat: Support blue/green updates (#468)

Co-authored-by: magreenbaum <magreenbaum>

README.md

@@ -245,6 +245,7 @@ Users have the ability to:
 | <a name="input_availability_zone"></a> [availability\_zone](#input\_availability\_zone) | The Availability Zone of the RDS instance | `string` | `null` | no |
 | <a name="input_backup_retention_period"></a> [backup\_retention\_period](#input\_backup\_retention\_period) | The days to retain backups for | `number` | `null` | no |
 | <a name="input_backup_window"></a> [backup\_window](#input\_backup\_window) | The daily time range (in UTC) during which automated backups are created if they are enabled. Example: '09:46-10:16'. Must not overlap with maintenance\_window | `string` | `null` | no |
+| <a name="input_blue_green_update"></a> [blue\_green\_update](#input\_blue\_green\_update) | Enables low-downtime updates using RDS Blue/Green deployments. | `map(string)` | `{}` | no |
 | <a name="input_ca_cert_identifier"></a> [ca\_cert\_identifier](#input\_ca\_cert\_identifier) | Specifies the identifier of the CA certificate for the DB instance | `string` | `null` | no |
 | <a name="input_character_set_name"></a> [character\_set\_name](#input\_character\_set\_name) | The character set name to use for DB encoding in Oracle instances. This can't be changed. See Oracle Character Sets Supported in Amazon RDS and Collations and Character Sets for Microsoft SQL Server for more information. This can only be set on creation | `string` | `null` | no |
 | <a name="input_cloudwatch_log_group_kms_key_id"></a> [cloudwatch\_log\_group\_kms\_key\_id](#input\_cloudwatch\_log\_group\_kms\_key\_id) | The ARN of the KMS Key to use when encrypting log data | `string` | `null` | no |

examples/complete-mysql/main.tf

@@ -49,10 +49,12 @@ module "db" {
   backup_window                   = "03:00-06:00"
   enabled_cloudwatch_logs_exports = ["general"]
   create_cloudwatch_log_group     = true
+  blue_green_update = {
+    enabled = true
+  }
 
-  backup_retention_period = 0
-  skip_final_snapshot     = true
-  deletion_protection     = false
+  skip_final_snapshot = true
+  deletion_protection = false
 
   performance_insights_enabled          = true
   performance_insights_retention_period = 7

main.tf

@@ -107,6 +107,7 @@ module "db_instance" {
   auto_minor_version_upgrade  = var.auto_minor_version_upgrade
   apply_immediately           = var.apply_immediately
   maintenance_window          = var.maintenance_window
+  blue_green_update           = var.blue_green_update
 
   snapshot_identifier              = var.snapshot_identifier
   copy_tags_to_snapshot            = var.copy_tags_to_snapshot

modules/db_instance/README.md

@@ -43,6 +43,7 @@ No modules.
 | <a name="input_availability_zone"></a> [availability\_zone](#input\_availability\_zone) | The Availability Zone of the RDS instance | `string` | `null` | no |
 | <a name="input_backup_retention_period"></a> [backup\_retention\_period](#input\_backup\_retention\_period) | The days to retain backups for | `number` | `null` | no |
 | <a name="input_backup_window"></a> [backup\_window](#input\_backup\_window) | The daily time range (in UTC) during which automated backups are created if they are enabled. Example: '09:46-10:16'. Must not overlap with maintenance\_window | `string` | `null` | no |
+| <a name="input_blue_green_update"></a> [blue\_green\_update](#input\_blue\_green\_update) | Enables low-downtime updates using RDS Blue/Green deployments. | `map(string)` | `{}` | no |
 | <a name="input_ca_cert_identifier"></a> [ca\_cert\_identifier](#input\_ca\_cert\_identifier) | Specifies the identifier of the CA certificate for the DB instance | `string` | `null` | no |
 | <a name="input_character_set_name"></a> [character\_set\_name](#input\_character\_set\_name) | The character set name to use for DB encoding in Oracle instances. This can't be changed. See Oracle Character Sets Supported in Amazon RDS and Collations and Character Sets for Microsoft SQL Server for more information. This can only be set on creation. | `string` | `null` | no |
 | <a name="input_cloudwatch_log_group_kms_key_id"></a> [cloudwatch\_log\_group\_kms\_key\_id](#input\_cloudwatch\_log\_group\_kms\_key\_id) | The ARN of the KMS Key to use when encrypting log data | `string` | `null` | no |

modules/db_instance/main.tf

@@ -70,6 +70,15 @@ resource "aws_db_instance" "this" {
   apply_immediately           = var.apply_immediately
   maintenance_window          = var.maintenance_window
 
+  # https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/blue-green-deployments.html
+  dynamic "blue_green_update" {
+    for_each = length(var.blue_green_update) > 0 ? [var.blue_green_update] : []
+
+    content {
+      enabled = try(blue_green_update.value.enabled, null)
+    }
+  }
+
   snapshot_identifier       = var.snapshot_identifier
   copy_tags_to_snapshot     = var.copy_tags_to_snapshot
   skip_final_snapshot       = var.skip_final_snapshot
@@ -81,7 +90,7 @@ resource "aws_db_instance" "this" {
 
   replicate_source_db     = var.replicate_source_db
   replica_mode            = var.replica_mode
-  backup_retention_period = var.backup_retention_period
+  backup_retention_period = length(var.blue_green_update) > 0 ? coalesce(var.backup_retention_period, 1) : var.backup_retention_period
   backup_window           = var.backup_window
   max_allocated_storage   = var.max_allocated_storage
   monitoring_interval     = var.monitoring_interval

modules/db_instance/variables.tf

@@ -249,6 +249,12 @@ variable "maintenance_window" {
   default     = null
 }
 
+variable "blue_green_update" {
+  description = "Enables low-downtime updates using RDS Blue/Green deployments."
+  type        = map(string)
+  default     = {}
+}
+
 variable "backup_retention_period" {
   description = "The days to retain backups for"
   type        = number

variables.tf

@@ -235,6 +235,12 @@ variable "maintenance_window" {
   default     = null
 }
 
+variable "blue_green_update" {
+  description = "Enables low-downtime updates using RDS Blue/Green deployments."
+  type        = map(string)
+  default     = {}
+}
+
 variable "backup_retention_period" {
   description = "The days to retain backups for"
   type        = number