Terraformで渡した引数によって処理を変える

概要

Terraformの実行時にわたした引数によって処理を変更し、作成されるリソースを変えてみたいと思います。

こんなかんじ

引数hikisuuがtrueであればサブネットを作成する。 falseであればしない。といったかんじ。
VPCはどちらの場合でも作成される。

variable "hikisuu" {
  type = bool
}

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

resource "aws_subnet" "subnet" {
  count      = var.hikisuu ? 1 : 0
  vpc_id     = aws_vpc.main.id
  cidr_block = "10.0.1.0/24"
}

実行してみる

こんなかんじになる。

true

$ terraform plan -var "hikisuu=true"
Refreshing Terraform state in-memory prior to plan...
The refreshed state will be used to calculate this plan, but will not be
persisted to local or remote state storage.


------------------------------------------------------------------------

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

Terraform will perform the following actions:

  # aws_subnet.subnet[0] will be created
  + resource "aws_subnet" "subnet" {
      + arn                             = (known after apply)
      + assign_ipv6_address_on_creation = false
      + availability_zone               = (known after apply)
      + availability_zone_id            = (known after apply)
      + cidr_block                      = "10.0.1.0/24"
      + id                              = (known after apply)
      + ipv6_cidr_block                 = (known after apply)
      + ipv6_cidr_block_association_id  = (known after apply)
      + map_public_ip_on_launch         = false
      + owner_id                        = (known after apply)
      + vpc_id                          = (known after apply)
    }

  # aws_vpc.main will be created
  + resource "aws_vpc" "main" {
      + arn                              = (known after apply)
      + assign_generated_ipv6_cidr_block = false
      + cidr_block                       = "10.0.0.0/16"
      + default_network_acl_id           = (known after apply)
      + default_route_table_id           = (known after apply)
      + default_security_group_id        = (known after apply)
      + dhcp_options_id                  = (known after apply)
      + enable_classiclink               = (known after apply)
      + enable_classiclink_dns_support   = (known after apply)
      + enable_dns_hostnames             = (known after apply)
      + enable_dns_support               = true
      + id                               = (known after apply)
      + instance_tenancy                 = "default"
      + ipv6_association_id              = (known after apply)
      + ipv6_cidr_block                  = (known after apply)
      + main_route_table_id              = (known after apply)
      + owner_id                         = (known after apply)
    }

Plan: 2 to add, 0 to change, 0 to destroy.

------------------------------------------------------------------------

Note: You didn't specify an "-out" parameter to save this plan, so Terraform
can't guarantee that exactly these actions will be performed if
"terraform apply" is subsequently run.

false

$ terraform plan -var "hikisuu=false"
Refreshing Terraform state in-memory prior to plan...
The refreshed state will be used to calculate this plan, but will not be
persisted to local or remote state storage.


------------------------------------------------------------------------

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

Terraform will perform the following actions:

  # aws_vpc.main will be created
  + resource "aws_vpc" "main" {
      + arn                              = (known after apply)
      + assign_generated_ipv6_cidr_block = false
      + cidr_block                       = "10.0.0.0/16"
      + default_network_acl_id           = (known after apply)
      + default_route_table_id           = (known after apply)
      + default_security_group_id        = (known after apply)
      + dhcp_options_id                  = (known after apply)
      + enable_classiclink               = (known after apply)
      + enable_classiclink_dns_support   = (known after apply)
      + enable_dns_hostnames             = (known after apply)
      + enable_dns_support               = true
      + id                               = (known after apply)
      + instance_tenancy                 = "default"
      + ipv6_association_id              = (known after apply)
      + ipv6_cidr_block                  = (known after apply)
      + main_route_table_id              = (known after apply)
      + owner_id                         = (known after apply)
    }

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

------------------------------------------------------------------------

Note: You didn't specify an "-out" parameter to save this plan, so Terraform
can't guarantee that exactly these actions will be performed if
"terraform apply" is subsequently run.

おわりに

ながくなった。

実践Terraform　AWSにおけるシステム設計とベストプラクティス (技術の泉シリーズ（NextPublishing）)