使用terraform创建数据库实例

我正在尝试创建只能在Intranet（也称为某个私有子网）中运行的 RDS . 只能向应用程序提供对它的访问权限 .

我在单独的 terraform 文件中创建了 vpc 配置link该文件包含 vpc 配置， routes ， nat 等 .

resource "aws_vpc" "vpc" {
  cidr_block = "10.0.0.0/16"
  enable_dns_support = true
  enable_dns_hostnames = true

  tags {
    Environment = "Dev"
  }
}

resource "aws_subnet" "intranet" {
  vpc_id = "${aws_vpc.vpc.id}"
  cidr_block = "10.0.1.0/24"
  availability_zone = "eu-central-1a"
  tags {
    Name = "Intranet"
    Environemnt = "Dev"
  }
}
....

resource "aws_route_table_association" "intranet" {
   subnet_id = "${aws_subnet.intranet.id}"
   route_table_id = "${aws_route_table.intranet_routetable.id}"
}

对于我的 RDS 配置，我创建了一个具有相似内容的单独的 terraform 文件

terraform {
  backend "s3" {
    bucket = "s3-terraform-state-backend"
    region = "eu-central-1"
    key = "common/terraform.tfstate"
  }
}

provider "aws" {
  region = "eu-central-1"
}

resource "aws_vpc" "vpc" {
  cidr_block = "10.0.0.0/16"
  enable_dns_support = true
  enable_dns_hostnames = true

  tags {
    Environment = "Dev"
  }
}

resource "aws_subnet" "intranet" {
  vpc_id = "${aws_vpc.vpc.id}"
  cidr_block = "10.0.1.0/24"
  availability_zone = "eu-central-1a"
  tags {
    Name = "Intranet"
    Environemnt = "Dev"
  }
}

# should contain configuration for common components (rds, sqs etc.)
resource "aws_db_subnet_group" "db_subnet" {
  name = "intranet"
  subnet_ids = ["${aws_subnet.intranet.id}"]
}

resource "aws_db_instance" "core" {
  name = "gj-core-db"
  engine = "postgres"

  allocated_storage = 10
  storage_type = "gp2"
  instance_class = "db.t2.micro"

  db_subnet_group_name = "${aws_db_subnet_group.db_subnet.name}"
}

基本上我从另一个文件复制 subnet 和 vpc 配置（因为我也需要它） . 文件本身在这里link

当我尝试 apply 配置时，我收到错误

* aws_db_subnet_group.db_subnet: Error creating DB Subnet Group: DBSubnetGroupDoesNotCoverEnoughAZs: DB Subnet Group doesn't meet availability zone coverage requirement
. Please add subnets to cover at least 2 availability zones. Current coverage: 1
        status code: 400, request id: 44e37b59-1db1-4519-847f-d35f5d150592

我只有一个子网 . 问题是什么？我应该创建更多的子网吗？或者使这个 intranet 子网覆盖更多区域？