如何用Terraform的rds-aurora模块创建选项组或为实例关联选项组

很多社区维护的terraform-aws-modules/rds-aurora模块默认没有暴露option_group_name参数，你可以通过以下方式解决：

1. 关联现有选项组 #

禁止模块自动创建实例，手动定义aws_rds_cluster_instance资源并关联已有选项组：

# 创建Aurora集群（不包含实例）
module "aurora_cluster" {
  source  = "terraform-aws-modules/rds-aurora/aws"
  version = "x.x.x" # 替换为你使用的模块版本

  cluster_identifier      = "my-aurora-cluster"
  engine                  = "aurora-mysql"
  engine_version          = "8.0.mysql_aurora.3.03.0"
  master_username         = "admin"
  master_password         = "your-secure-password"
  create_db_instance      = false # 禁用模块自动创建实例
  # 补充集群必要配置（如VPC、安全组等）
}

# 手动创建实例并关联现有选项组
resource "aws_rds_cluster_instance" "aurora_instance" {
  identifier         = "my-aurora-instance"
  cluster_identifier = module.aurora_cluster.cluster_id
  instance_class     = "db.t3.small"
  option_group_name  = "arn:aws:rds:us-east-1:123456789012:option-group:my-existing-option-group" # 替换为你的选项组ARN或名称
  # 补充实例必要配置
}

2. 创建新选项组并关联 #

先定义aws_db_option_group资源，再关联到手动创建的实例：

# 创建Aurora专用选项组
resource "aws_db_option_group" "aurora_option_group" {
  name                     = "my-aurora-option-group"
  option_group_description = "Custom option group for Aurora cluster"
  engine_name              = "aurora-mysql" # 匹配集群引擎
  major_engine_version     = "8.0" # 匹配引擎大版本

  # 添加需要的选项，示例为MEMCACHED
  option {
    option_name = "MEMCACHED"
    option_settings {
      name  = "MAX_CONNECTIONS"
      value = "1000"
    }
  }
}

# 创建Aurora集群（不包含实例）
module "aurora_cluster" {
  source  = "terraform-aws-modules/rds-aurora/aws"
  version = "x.x.x"

  cluster_identifier      = "my-aurora-cluster"
  engine                  = "aurora-mysql"
  engine_version          = "8.0.mysql_aurora.3.03.0"
  master_username         = "admin"
  master_password         = "your-secure-password"
  create_db_instance      = false
  # 补充集群必要配置
}

# 关联新选项组到实例
resource "aws_rds_cluster_instance" "aurora_instance" {
  identifier         = "my-aurora-instance"
  cluster_identifier = module.aurora_cluster.cluster_id
  instance_class     = "db.t3.small"
  option_group_name  = aws_db_option_group.aurora_option_group.name
  # 补充实例必要配置
}

替代方案：扩展模块 #

如果需要长期通过模块直接传递选项组参数，可以forkterraform-aws-modules/rds-aurora仓库，在模块的variables.tf中添加：

variable "option_group_name" {
  description = "Name of the option group to associate with the instance"
  type        = string
  default     = ""
}

然后在模块内的aws_rds_cluster_instance资源中加入：

option_group_name = var.option_group_name != "" ? var.option_group_name : null

之后就能直接通过模块变量传递选项组名称了。

内容的提问来源于stack exchange，提问作者Ruslynn