amazon-web-services - 使用 terraform 创建数据库实例

Question

我正在尝试创建只能在 Intranet(又名某些私有(private)子网)中运行的 RDS。对它的访问将只提供给应用程序。

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了 subnet 和 vpc 配置(因为我在这里也需要它)。文件本身在这里link

当我尝试应用配置时出现错误

* 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？我应该创建更多子网吗？或者使这个 intranet 子网覆盖更多区域？

Answer 1

一个子网不能跨越多个可用区。您应该创建多个子网并将它们分配给您正在创建的子网组。这是为了保证HA。如果您配置多可用区 RDS 数据库实例并且您的主数据库发生故障，RDS 将确保您的数据库移动到不同的可用区(具有相同端点)。

对于子网组，AWS 强制要求每个子网组的子网分布在多个可用区中。可以找到更多详细信息here .

以下是 AWS 文档中的相关部分。

Each DB subnet group should have subnets in at least two Availability Zones in a given region. When creating a DB instance in VPC, you must select a DB subnet group. Amazon RDS uses that DB subnet group and your preferred Availability Zone to select a subnet and an IP address within that subnet to associate with your DB instance. If the primary DB instance of a Multi-AZ deployment fails, Amazon RDS can promote the corresponding standby and subsequently create a new standby using an IP address of the subnet in one of the other Availability Zones