地形>在安全组上强制新资源

我有一个非常简单的地形代码:

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

module ec2 {
  source = "./ec2_instance"
  name = "EC2 Instance 1"
} 

如果模块是:

variable "name" {
    default = "Default Name from ec2_instance.tf"
}

resource "aws_instance" "example" {
  ami = "ami-e5083683"
  instance_type = "t2.nano"
  subnet_id = "subnet-3e976259"
  associate_public_ip_address = true
  security_groups = [ "sg-7310e10b" ]
  tags {
    Name = "${var.name}"
  }
}

当我第一次运行它时,我得到这个输出:

security_groups.#:            "" => "1"
security_groups.1642973399:   "" => "sg-7310e10b"

但是,下次我尝试 plan 我得到:

  security_groups.#:            "0" => "1" (forces new resource)
  security_groups.1642973399:   "" => "sg-7310e10b" (forces new resource)

给出了什么?!