amazon-web-services - Terraform 错误创建子网依赖

Question

我正在尝试启动并运行一个 documentdb 集群，并让它在我创建的私有(private)子网中运行。

在没有 depends_on 的情况下运行下面的配置我收到以下错误消息，因为尚未创建子网:

Error: error creating DocDB cluster: DBSubnetGroupNotFoundFault: DB subnet group 'subnet-0b97a3f5bf6db758f' does not exist.
status code: 404, request id: 59b75d23-50a4-42f9-99a3-367af58e6e16

添加了依赖设置以等待子网创建但遇到问题。

  cluster_identifier      = "my-docdb-cluster"
  engine                  = "docdb"
  master_username         = "myusername"
  master_password         = "mypassword"
  backup_retention_period = 5
  preferred_backup_window = "07:00-09:00"
  skip_final_snapshot     = true
  apply_immediately       = true
  db_subnet_group_name    = aws_subnet.eu-west-3a-private
  depends_on = [aws_subnet.eu-west-3a-private]
}

在运行 terraform apply 时，我收到配置错误:

Error: error creating DocDB cluster: DBSubnetGroupNotFoundFault: DB subnet group 'subnet-0b97a3f5bf6db758f' does not exist.
status code: 404, request id: 8b992d86-eb7f-427e-8f69-d05cc13d5b2d

on main.tf line 230, in resource "aws_docdb_cluster" "docdb":
230: resource "aws_docdb_cluster" "docdb" 

Answer 1

数据库子网组本身就是一种逻辑资源，它告诉 AWS 它可以在 VPC 中的什么地方安排数据库实例。它不是直接引用子网，而这正是您要在那里做的事情。

要创建数据库子网组，您应该使用 aws_db_subnet_group resource .然后在创建数据库实例或集群时直接按名称引用它。

一个基本的例子是这样的:

resource "aws_vpc" "example" {
  cidr_block = "10.0.0.0/16"
}

resource "aws_subnet" "eu-west-3a" {
  vpc_id            = aws_vpc.example.id
  availability_zone = "a"
  cidr_block        = "10.0.1.0/24"

  tags = {
    AZ = "a"
  }
}

resource "aws_subnet" "eu-west-3b" {
  vpc_id            = aws_vpc.example.id
  availability_zone = "b"
  cidr_block        = "10.0.2.0/24"

  tags = {
    AZ = "b"
  }
}

resource "aws_db_subnet_group" "example" {
  name       = "main"

  subnet_ids = [
    aws_subnet.eu-west-3a.id,
    aws_subnet.eu-west-3b.id
  ]

  tags = {
    Name = "My DB subnet group"
  }
}

resource "aws_db_instance" "example" {
  allocated_storage    = 20
  storage_type         = "gp2"
  engine               = "mysql"
  engine_version       = "5.7"
  instance_class       = "db.t2.micro"
  name                 = "mydb"
  username             = "foo"
  password             = "foobarbaz"
  parameter_group_name = "default.mysql5.7"
  db_subnet_group_name = aws_db_subnet_group.example.name
}

同样的事情适用于 Elasticache subnet groups使用 aws_elasticache_subnet_group resource .

---

还值得注意的是，将 depends_on 添加到已经通过插值引用依赖资源的资源中不会执行任何操作。 depends_on 元参数适用于不公开仅直接提供此依赖信息的参数的资源。