別のstateファイルの値を参照する

概要

リモートステートをつかって別のstateファイルの値を参照して見たいと思います。
これによって stateをまたいでいろいろできたりするのでstateの分離等もしやすくなるかもしれないしならないかもしれない。

EC2インスタンスを作成するstateと、それにEIPをアタッチするstateが別なんだけれどもアタッチができるよっていうのをやります。

前提

前提です。

バージョン

Terraformのバージョン等はこんなかんじ。

$ terraform --version
Terraform v0.12.18
+ provider.aws v2.43.0

EC2インスタンスをつくるstateのtfファイル

ひとつめのstateです。

provider "aws" {
  region = "ap-northeast-1"
}
terraform {
  backend "s3" {
    bucket = "mybucket"
    key    = "terraform.tfstate"
    region = "ap-northeast-1"
  }
}
resource "aws_instance" "example" {
  ami           = "ami-068a6cefc24c301d2"
  instance_type = "t3.micro"
  subnet_id     = aws_subnet.subnet.id
}
resource "aws_vpc" "main" {
  cidr_block = "10.0.0.0/16"
}
resource "aws_subnet" "subnet" {
  cidr_block = "10.0.1.0/24"
  vpc_id     = aws_vpc.main.id
}
resource "aws_internet_gateway" "igw" {
  vpc_id = aws_vpc.main.id
}
output "instance_id" {
  value = aws_instance.example.id
}

EIPをアタッチするstateのtfファイル

2つめです。

provider "aws" {
  region = "ap-northeast-1"
}
data "terraform_remote_state" "remote_state" {
  backend = "s3"
  config = {
    bucket = "mybucket"
    key    = "terraform.tfstate"
    region = "ap-northeast-1"
  }
}
resource "aws_eip" "eip" {
  instance = data.terraform_remote_state.remote_state.outputs.instance_id
}

うごかしてみる

うごかしてみます

EC2インスタンスをつくるstateのtfファイル

こんなかんじになります。
参照される値はoutputで出力する必要があります。

$ terraform apply
~~~省略~~~
Apply complete! Resources: 1 added, 0 changed, 1 destroyed.

Outputs:

instance_id = i-02814f190bddac514

EIPをアタッチするstateのtfファイル

EIPがアタッチされていることがわかりますね

$ terraform apply
data.terraform_remote_state.remote_state: Refreshing state...
aws_eip.eip: Refreshing state... [id=eipalloc-08169d0c5eaa117f4]

An execution plan has been generated and is shown below.
Resource actions are indicated with the following symbols:
-/+ destroy and then create replacement

Terraform will perform the following actions:

  # aws_eip.eip is tainted, so must be replaced
-/+ resource "aws_eip" "eip" {
      + allocation_id     = (known after apply)
      + association_id    = (known after apply)
      ~ domain            = "vpc" -> (known after apply)
      ~ id                = "eipalloc-08169d0c5eaa117f4" -> (known after apply)
      + instance          = "i-02814f190bddac514"
      + network_interface = (known after apply)
      + private_dns       = (known after apply)
      + private_ip        = (known after apply)
      ~ public_dns        = "ec2-3-114-205-18.ap-northeast-1.compute.amazonaws.com" -> (known after apply)
      ~ public_ip         = "3.114.205.18" -> (known after apply)
      ~ public_ipv4_pool  = "amazon" -> (known after apply)
      - tags              = {} -> null
      ~ vpc               = true -> (known after apply)
    }

Plan: 1 to add, 0 to change, 1 to destroy.

Do you want to perform these actions?
  Terraform will perform the actions described above.
  Only 'yes' will be accepted to approve.

  Enter a value: yes

aws_eip.eip: Destroying... [id=eipalloc-08169d0c5eaa117f4]
aws_eip.eip: Destruction complete after 1s
aws_eip.eip: Creating...
aws_eip.eip: Creation complete after 1s [id=eipalloc-0bd8be7d66afa0c58]

Apply complete! Resources: 1 added, 0 changed, 1 destroyed.

おわりに

べんりですね

Terraform: Up and Running: Writing Infrastructure as Code