[Terraform] count 실습 (aws ec2, vpc, subnet 생성 시나리오) +cloudnet 스터디 악분님 제공

💡cloudNet@ 팀의 가시다 님이 진행하는 Terraform 101 Study 4기 2주차 내용으로,
[테라폼으로 시작하는 IaC] 도서를 참조하였습니다. 감사합니다..

 

cloudnet 스터디 악분님이 count를 실습해볼 수 있는 좋은 시나리오를 공유해주셨습니다. (감사합니다)

한번 따라서 정리해보도록 하겠습니다.

 

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1. count 실습 (스터디 악분님 제공)

다음과 같이 실습환경을 구성한다. 총 10개의 시나리오를 통해 학습한 내용을 확인해 보겠다.

사진-1

 

시나리오 1. aws_subnet

- AWS VPC Subnet 테라폼 코드 작성

- 요구사항 : subnet cidr를 변수로 입력

 

다음과 같이 main.tf, variables.tf, terraform.tfvars 총 3개의 파일을 작성한다.

# main.tf
resource "aws_vpc" "main" {
  cidr_block = var.vpc_cidr

  tags = {
    Name = "terraform VPC"
  }
}

resource "aws_subnet" "main" {
  vpc_id     = aws_vpc.main.id
  cidr_block = **var.subnet_cidr**
}

**output "myvpc_id" {
  value = aws_vpc.main.id
}**

# variables.tf
variable "vpc_cidr" {
  type = string
}

**variable "subnet_cidr" {
  type = string
}**

# terraform.tfvars
vpc_cidr            = "192.168.0.0/16"
subnet_cidr = "192.168.1.0/24"

 

배포 실행 결과

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시나리오 2. index element length

- 요구사항 : subnet cidr 변수 값을 여러 개 입력받도록 구성

 

다음과 같이 main.tf, variables.tf, terraform.tfvars 총 3개의 파일을 수정한다.

# main.tf
resource "aws_vpc" "main" {
  cidr_block = var.vpc_cidr

  tags = {
    Name = "terraform VPC"
  }
}

resource "aws_subnet" "main" {
  **count = length(var.subnet_cidr)**
  vpc_id     = aws_vpc.main.id
  cidr_block = **element(var.subnet_cidr, count.index)**
}

output "myvpc_id" {
  value = aws_vpc.main.id
}

# variables.tf
variable "vpc_cidr" {
  type = string
}

**variable "subnet_cidr" {
  type = list(string)
}**

# terraform.tfvars
vpc_cidr            = "192.168.0.0/16"
subnet_cidr = **[**"192.168.1.0/24"**, "192.168.2.0/24"]**

 

배포 실행 결과

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시나리오 3. aws_subnet_arg_az (AZ for the subnet)

- 요구사항 : 서브넷이 배치되는 AZ 설정이 필요하다. AZ는 변수로 입력하도록 구성

 

# main.tf
resource "aws_vpc" "main" {
  cidr_block = var.vpc_cidr

  tags = {
    Name = "terraform VPC"
  }
}

resource "aws_subnet" "main" {
  **count = length(var.subnet_cidr)**
  vpc_id     = aws_vpc.main.id
  cidr_block = **element(var.subnet_cidr, count.index)
  availability_zone = element(var.subnet_az, count.index)**
}

output "myvpc_id" {
  value = aws_vpc.main.id
}

# variables.tf
variable "vpc_cidr" {
  type = string
}

variable "subnet_cidr" {
  type = list(string)
}

**variable "subnet_az" {
  type = list(string)
}**

# terraform.tfvars
vpc_cidr            = "192.168.0.0/16"
subnet_cidr = ["192.168.1.0/24", "192.168.2.0/24"]
**subnet_az = ["ap-northeast-2a", "ap-northeast-2c"]**

 

배포 실행 결과, AZ까지 잘 나누어져 콘솔에서도 정렬이 분리되었다.

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시나리오 4. aws_subnet-arg_tags (A map of tags assigned to the resource) map

- 요구사항 : 위 시나리오 3 이미지를 보면 name이 비어있다. subnet tag 설정을 추가한다.

 

mian.tf 을 다음과 같이 수정한다.

# main.tf
resource "aws_vpc" "main" {
  cidr_block = var.vpc_cidr

  tags = {
    Name = "terraform VPC"
  }
}

resource "aws_subnet" "main" {
  **count = length(var.subnet_cidr)**
  vpc_id     = aws_vpc.main.id
  cidr_block = **element(var.subnet_cidr, count.index)
  availability_zone = element(var.subnet_az, count.index)**
}

output "myvpc_id" {
  value = aws_vpc.main.id
}

 

배포 실행 결과

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---

---

시나리오 5. map

- 요구사항 : subnet tag를 설정하는 변수 생성

# main.tf
resource "aws_vpc" "main" {
  cidr_block = var.vpc_cidr

  tags = {
    Name = "terraform VPC"
  }
}

resource "aws_subnet" "main" {
  count = length(var.subnet_cidr)
  vpc_id     = aws_vpc.main.id
  cidr_block = element(var.subnet_cidr, count.index)
  availability_zone = element(var.subnet_az, count.index)

  **tags = element(var.subnet_tag, count.index)**
}

output "myvpc_id" {
  value = aws_vpc.main.id
}

# variables.tf
variable "vpc_cidr" {
  type = string
}

variable "subnet_cidr" {
  type = list(string)
}

variable "subnet_az" {
  type = list(string)
}

**variable "subnet_tag" {
  type = list(map(string))
}**

# terraform.tfvars
vpc_cidr            = "192.168.0.0/16"
subnet_cidr = ["192.168.1.0/24", "192.168.2.0/24"]
subnet_az = ["ap-northeast-2a", "ap-northeast-2c"]
**subnet_tag = [
  {
    Name = "public-subnet"
    Environment = "dev"
  },
  {
    Name = "private-subnet"
    Environment = "dev"
  }
]**

 

배포 실행 결과

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시나리오 6. (리팩토링) - map_list_object

- 요구사항 : subnet 설정 변수를 한 변수로 설정하도록 리팩토링 구성

# main.tf
resource "aws_vpc" "main" {
  cidr_block = var.vpc_cidr

  tags = {
    Name = "terraform VPC"
  }
}

resource "aws_subnet" "main" {
  count = length(var.subnets) # subnet_cidr > subnets 변경
  vpc_id     = aws_vpc.main.id
  cidr_block = **var.subnets[count.index].cidr # elment에서 변경**
  availability_zone = **var.subnets[count.index].az**

  tags = **var.subnets[count.index].tags #elment에서 변경**
}

output "myvpc_id" {
  value = aws_vpc.main.id
}

# variables.tf
variable "vpc_cidr" {
  type = string
}

**variable "subnets" {
  type = list(object({
    cidr = string
    az = string
    tags = map(string)
  }))
}**

# terraform.tfvars
vpc_cidr            = "192.168.0.0/16"

**subnets = [
  {
    cidr = "192.168.1.0/24",
    az = "ap-northeast-2a",
    tags = {
      Name = "public-subnet"
      Environment = "dev"
    }
  },
  {
    cidr = "192.168.2.0/24",
    az = "ap-northeast-2c",
    tags = {
      Name = "private-subnet"
      Environment = "dev"
    }
  }**
]

 

배포 실행 결과

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시나리오 7. 장애 상황 재현

- 요구사항 : 오류 확인 후 코드 수정

사진-16

 

기존 VPC, Subnet 구성은 제거하였고, 다음과 같이 실습 환경을 구성/배포 한다.

# main
resource "aws_vpc" "main" {
  cidr_block = var.vpc_cidr

  tags = {
    Name = "terraform VPC"
  }
}

resource "aws_subnet" "main" {
  count = length(var.subnets)

  vpc_id     = aws_vpc.main.id
  cidr_block = var.subnets[count.index].cidr
  availability_zone = var.subnets[count.index].az

  tags = var.subnets[count.index].tags
}

resource "aws_instance" "server" {
  ami           = "ami-0e8bd0820b6e1360b"
  instance_type = "t4g.nano"
  subnet_id = aws_subnet.main[1].id
  # index 접근 방법 오류 해결 코드
  # subnet_id = index(aws_subnet.main.*.cidr_block, "192.168.2.0/24")
  tags = {
    Name = "Terraform demo"
  }
}

# 실습 편리를 위해 output 추가
output "myvpc_id" {
  value = aws_vpc.main.id
}

# variables.tf
variable "vpc_cidr" {
  type = string
}

variable "subnets" {
  type = list(object({
    cidr = string
    az = string
    tags = map(string)
  }))
}

# terraform.tfvars
vpc_cidr            = "192.168.0.0/16"

subnets = [
  # (유투브 7번째 시나리오) terrafprm apply 이 후, 첫 번째 요소를 주석하세요
  {
    cidr = "192.168.1.0/24",
    az = "ap-northeast-2a",
    tags = {
      Name = "public-subnet"
      Environment = "dev"
    }
  },
  # (유투브 8번째 시나리오) terrafprm apply 이 후, 주석을 해제하고 terraform apply해보세요
  # {
  #   cidr = "192.168.5.0/24",
  #   az = "ap-northeast-2a",
  #   tags = {
  #     Name = "public-subnet"
  #     Environment = "dev"
  #   }
  # },
  {
    cidr = "192.168.2.0/24",
    az = "ap-northeast-2a",
    tags = {
      Name = "private-subnet"
      Environment = "dev"
    }
  },
  {
    cidr = "192.168.3.0/24",
    az = "ap-northeast-2a",
    tags = {
      Name = "public-subnet"
      Environment = "dev"
    }
  },
  {
    cidr = "192.168.4.0/24",
    az = "ap-northeast-2c",
    tags = {
      Name = "private-subnet"
      Environment = "dev"
    }
  }
]

 

다시 생성한 VPC와 4개의 서브넷, 그리고 EC2 1개가 생성되었다. EC2는 private-subnet 192.168.2.0/24 서브넷으로 구성되어 있다.

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!! 장애 재현 : terraform.tfvars 수정

해당 부분 주석처리하여 장애를 발생시킨다.

vpc_cidr            = "192.168.0.0/16"

subnets = [
  # (유투브 7번째 시나리오) terrafprm apply 이 후, 첫 번째 요소를 주석하세요
  #{
  #  cidr = "192.168.1.0/24",
  #  az = "ap-northeast-2a",
  #  tags = {
  #    Name = "public-subnet"
  #    Environment = "dev"
  #  }
  #},
  # (유투브 8번째 시나리오) terrafprm apply 이 후, 주석을 해제하고 terraform apply해보세요
  # {
  #   cidr = "192.168.5.0/24",
  #   az = "ap-northeast-2a",
  #   tags = {
  #     Name = "public-subnet"
  #     Environment = "dev"
  #   }
  # },
  {
    cidr = "192.168.2.0/24",
    az = "ap-northeast-2a",
    tags = {
      Name = "private-subnet"
      Environment = "dev"
    }
  },
  {
    cidr = "192.168.3.0/24",
    az = "ap-northeast-2a",
    tags = {
      Name = "public-subnet"
      Environment = "dev"
    }
  },
  {
    cidr = "192.168.4.0/24",
    az = "ap-northeast-2c",
    tags = {
      Name = "private-subnet"
      Environment = "dev"
    }
  }
]

 

plan을 실행해 변경 내용을 확인해보겠다.

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# aws_subnet.main[0] must be replaced
-/+ resource "aws_subnet" "main" {
      ~ arn                                            = "arn:aws:ec2:ap-northeast-2:891376941699:subnet/subnet-070df28e60c3fef07" -> (known after apply)
      ~ availability_zone_id                           = "apne2-az1" -> (known after apply)
      ~ cidr_block                                     = "192.168.1.0/24" -> "192.168.2.0/24" # forces replacement
      - enable_lni_at_device_index                     = 0 -> null
      ~ id                                             = "subnet-070df28e60c3fef07" -> (known after apply)
      + ipv6_cidr_block_association_id                 = (known after apply)
      - map_customer_owned_ip_on_launch                = false -> null
      ~ owner_id                                       = "891376941699" -> (known after apply)
      ~ private_dns_hostname_type_on_launch            = "ip-name" -> (known after apply)
      ~ tags                                           = {
            "Environment" = "dev"
          ~ "Name"        = "public-subnet" -> "private-subnet"
        }
      ~ tags_all                                       = {
          ~ "Name"        = "public-subnet" -> "private-subnet"
            # (1 unchanged element hidden)
        }
        # (11 unchanged attributes hidden)
    }

  # aws_subnet.main[1] must be replaced
-/+ resource "aws_subnet" "main" {
      ~ arn                                            = "arn:aws:ec2:ap-northeast-2:891376941699:subnet/subnet-040a2fc0e8c278c0a" -> (known after apply)
      ~ availability_zone_id                           = "apne2-az1" -> (known after apply)
      ~ cidr_block                                     = "192.168.2.0/24" -> "192.168.3.0/24" # forces replacement
      - enable_lni_at_device_index                     = 0 -> null
      ~ id                                             = "subnet-040a2fc0e8c278c0a" -> (known after apply)
      + ipv6_cidr_block_association_id                 = (known after apply)
      - map_customer_owned_ip_on_launch                = false -> null
      ~ owner_id                                       = "891376941699" -> (known after apply)
      ~ private_dns_hostname_type_on_launch            = "ip-name" -> (known after apply)
      ~ tags                                           = {
            "Environment" = "dev"
          ~ "Name"        = "private-subnet" -> "public-subnet"
        }
      ~ tags_all                                       = {
          ~ "Name"        = "private-subnet" -> "public-subnet"
            # (1 unchanged element hidden)
        }
        # (11 unchanged attributes hidden)
    }

  # aws_subnet.main[2] must be replaced
-/+ resource "aws_subnet" "main" {
      ~ arn                                            = "arn:aws:ec2:ap-northeast-2:891376941699:subnet/subnet-07846067fffb97419" -> (known after apply)
      ~ availability_zone                              = "ap-northeast-2a" -> "ap-northeast-2c" # forces replacement
      ~ availability_zone_id                           = "apne2-az1" -> (known after apply)
      ~ cidr_block                                     = "192.168.3.0/24" -> "192.168.4.0/24" # forces replacement
      - enable_lni_at_device_index                     = 0 -> null
      ~ id                                             = "subnet-07846067fffb97419" -> (known after apply)
      + ipv6_cidr_block_association_id                 = (known after apply)
      - map_customer_owned_ip_on_launch                = false -> null
      ~ owner_id                                       = "891376941699" -> (known after apply)
      ~ private_dns_hostname_type_on_launch            = "ip-name" -> (known after apply)
      ~ tags                                           = {
            "Environment" = "dev"
          ~ "Name"        = "public-subnet" -> "private-subnet"
        }
      ~ tags_all                                       = {
          ~ "Name"        = "public-subnet" -> "private-subnet"
            # (1 unchanged element hidden)
        }
        # (10 unchanged attributes hidden)
    }

  # aws_subnet.main[3] will be destroyed
  # (because index [3] is out of range for count)
  - resource "aws_subnet" "main" {
      - arn                                            = "arn:aws:ec2:ap-northeast-2:891376941699:subnet/subnet-0223cb176694dda91" -> null        
      - assign_ipv6_address_on_creation                = false -> null
      - availability_zone                              = "ap-northeast-2c" -> null
      - availability_zone_id                           = "apne2-az3" -> null
      - cidr_block                                     = "192.168.4.0/24" -> null
      - enable_dns64                                   = false -> null
      - enable_lni_at_device_index                     = 0 -> null
      - enable_resource_name_dns_a_record_on_launch    = false -> null
      - enable_resource_name_dns_aaaa_record_on_launch = false -> null
      - id                                             = "subnet-0223cb176694dda91" -> null
      - ipv6_native                                    = false -> null
      - map_customer_owned_ip_on_launch                = false -> null
      - map_public_ip_on_launch                        = false -> null
      - owner_id                                       = "891376941699" -> null
      - private_dns_hostname_type_on_launch            = "ip-name" -> null
      - tags                                           = {
          - "Environment" = "dev"
          - "Name"        = "private-subnet"
        } -> null
      - tags_all                                       = {
          - "Environment" = "dev"
          - "Name"        = "private-subnet"
        } -> null
      - vpc_id                                         = "vpc-0c564090f849155b1" -> null
        # (4 unchanged attributes hidden)
    }

위 내용을 보면 192.168.1.0/24 서브넷을 주석처리하여 제거함으로서 하나씩 앞으로 당겨진 것을 볼 수 있다.

 

실행 결과를 확인해보겠다. 192.168.1.0/24 서브넷이 실종되었고, EC2 인스턴스는 192.168.3.0/24 대역으로 할당받았다.

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시나리오 8. 장애 상황 재현 2

- 요구사항 : 오류 확인 후 코드 수정

테라폼 변수에서 subnet 추가 후 에러 발생

사진-23

 

terraform.tfvars 파일 내용을 수정한다.

# terraform.tfvars
vpc_cidr            = "192.168.0.0/16"

subnets = [
  {
    cidr = "192.168.1.0/24",
    az = "ap-northeast-2a",
    tags = {
      Name = "public-subnet"
      Environment = "dev"
    }
  },
  # 다음 서브넷 추가!!!
   {
     cidr = "192.168.5.0/24",
     az = "ap-northeast-2a",
     tags = {
       Name = "public-subnet"
       Environment = "dev"
     }
   },
  {
    cidr = "192.168.2.0/24",
    az = "ap-northeast-2a",
    tags = {
      Name = "private-subnet"
      Environment = "dev"
    }
  },
  {
    cidr = "192.168.3.0/24",
    az = "ap-northeast-2a",
    tags = {
      Name = "public-subnet"
      Environment = "dev"
    }
  },
  {
    cidr = "192.168.4.0/24",
    az = "ap-northeast-2c",
    tags = {
      Name = "private-subnet"
      Environment = "dev"
    }
  }
]

 

수정하여 terraform apply 진행 시, 다음과 같이 에러가 발생한다. 192.168.4.0/24, 192.168.3.0/24 서브넷이 충돌한다는 것인데 이유가 무엇일까?

사진-24

 

현재 생성된 서브넷

사진-25

 

일단 서버 생성 로그를 확인해보면, 기존 192.168.3.0/24 대역에서 새로운 대역으로 변경된 것을 확인 가능하다.

# aws_instance.server must be replaced
-/+ resource "aws_instance" "server" {
      ~ arn                                  = "arn:aws:ec2:ap-northeast-2:891376941699:instance/i-0605531f9d99f6d34" -> (known after apply)      
      ~ associate_public_ip_address          = false -> (known after apply)
      ~ availability_zone                    = "ap-northeast-2a" -> (known after apply)
      ~ cpu_core_count                       = 2 -> (known after apply)
      ~ cpu_threads_per_core                 = 1 -> (known after apply)
      ~ disable_api_stop                     = false -> (known after apply)
      ~ disable_api_termination              = false -> (known after apply)
      ~ ebs_optimized                        = false -> (known after apply)
      - hibernation                          = false -> null
      + host_id                              = (known after apply)
      + host_resource_group_arn              = (known after apply)
      + iam_instance_profile                 = (known after apply)
      ~ id                                   = "i-0605531f9d99f6d34" -> (known after apply)
      ~ instance_initiated_shutdown_behavior = "stop" -> (known after apply)
      + instance_lifecycle                   = (known after apply)
      ~ instance_state                       = "running" -> (known after apply)
      ~ ipv6_address_count                   = 0 -> (known after apply)
      ~ ipv6_addresses                       = [] -> (known after apply)
      + key_name                             = (known after apply)
      ~ monitoring                           = false -> (known after apply)
      + outpost_arn                          = (known after apply)
      + password_data                        = (known after apply)
      + placement_group                      = (known after apply)
      ~ placement_partition_number           = 0 -> (known after apply)
      ~ primary_network_interface_id         = "eni-0069722efa458f0f9" -> (known after apply)
      ~ private_dns                          = "ip-192-168-3-13.ap-northeast-2.compute.internal" -> (known after apply)
      ~ private_ip                           = "192.168.3.13" -> (known after apply)
      + public_dns                           = (known after apply)
      + public_ip                            = (known after apply)
      ~ secondary_private_ips                = [] -> (known after apply)
      ~ security_groups                      = [] -> (known after apply)
      + spot_instance_request_id             = (known after apply)
      ~ subnet_id                            = "subnet-0c3a63cee06465cf7" # forces replacement -> (known after apply) # forces replacement        
        tags                                 = {
            "Name" = "Terraform demo"
        }
      ~ tenancy                              = "default" -> (known after apply)
      + user_data                            = (known after apply)
      + user_data_base64                     = (known after apply)
      ~ vpc_security_group_ids               = [
          - "sg-0550d5c309aac5d32",
        ] -> (known after apply)
        # (6 unchanged attributes hidden)

 

다음 subnet 생성 로그를 확인해보겠다. 요약하자면,

• priveate 192.168.2.0 → public 192.168.1.0
• public 192.168.3.0 → public 192.168.5.0 (기존 EC2에서 사용되던 subnet)
• private 192.168.4.0 → private 192.168.2.0
• public 192.168.3.0 →생성 error
• private 192.168.4.0 → 생성 error

aws_subnet.main[0] must be replaced
-/+ resource "aws_subnet" "main" {
      ~ arn                                            = "arn:aws:ec2:ap-northeast-2:891376941699:subnet/subnet-0b0c16c4004fb1225" -> (known after apply)
      ~ availability_zone_id                           = "apne2-az1" -> (known after apply)
      ~ cidr_block                                     = "192.168.2.0/24" -> "192.168.1.0/24" # forces replacement
      - enable_lni_at_device_index                     = 0 -> null
      ~ id                                             = "subnet-0b0c16c4004fb1225" -> (known after apply)
      + ipv6_cidr_block_association_id                 = (known after apply)
      - map_customer_owned_ip_on_launch                = false -> null
      ~ owner_id                                       = "891376941699" -> (known after apply)
      ~ private_dns_hostname_type_on_launch            = "ip-name" -> (known after apply)
      ~ tags                                           = {
            "Environment" = "dev"
          ~ "Name"        = "private-subnet" -> "public-subnet"
        }
      ~ tags_all                                       = {
          ~ "Name"        = "private-subnet" -> "public-subnet"
            # (1 unchanged element hidden)
        }
        # (11 unchanged attributes hidden)
    }

  # aws_subnet.main[1] must be replaced
-/+ resource "aws_subnet" "main" {
      ~ arn                                            = "arn:aws:ec2:ap-northeast-2:891376941699:subnet/subnet-0c3a63cee06465cf7" -> (known after apply)
      ~ availability_zone_id                           = "apne2-az1" -> (known after apply)
      ~ cidr_block                                     = "192.168.3.0/24" -> "192.168.5.0/24" # forces replacement
      - enable_lni_at_device_index                     = 0 -> null
      ~ id                                             = "subnet-0c3a63cee06465cf7" -> (known after apply)
      + ipv6_cidr_block_association_id                 = (known after apply)
      - map_customer_owned_ip_on_launch                = false -> null
      ~ owner_id                                       = "891376941699" -> (known after apply)
      ~ private_dns_hostname_type_on_launch            = "ip-name" -> (known after apply)
        tags                                           = {
            "Environment" = "dev"
            "Name"        = "public-subnet"
        }
        # (12 unchanged attributes hidden)
    }

  # aws_subnet.main[2] must be replaced
-/+ resource "aws_subnet" "main" {
      ~ arn                                            = "arn:aws:ec2:ap-northeast-2:891376941699:subnet/subnet-0c458aa6685399eb0" -> (known after apply)
      ~ availability_zone                              = "ap-northeast-2c" -> "ap-northeast-2a" # forces replacement
      ~ availability_zone_id                           = "apne2-az3" -> (known after apply)
      ~ cidr_block                                     = "192.168.4.0/24" -> "192.168.2.0/24" # forces replacement
      - enable_lni_at_device_index                     = 0 -> null
      ~ id                                             = "subnet-0c458aa6685399eb0" -> (known after apply)
      + ipv6_cidr_block_association_id                 = (known after apply)
      - map_customer_owned_ip_on_launch                = false -> null
      ~ owner_id                                       = "891376941699" -> (known after apply)
      ~ private_dns_hostname_type_on_launch            = "ip-name" -> (known after apply)
        tags                                           = {
            "Environment" = "dev"
            "Name"        = "private-subnet"
        }
        # (11 unchanged attributes hidden)
    }

  # aws_subnet.main[3] will be created
  + resource "aws_subnet" "main" {
      + arn                                            = (known after apply)
      + assign_ipv6_address_on_creation                = false
      + availability_zone                              = "ap-northeast-2a"
      + availability_zone_id                           = (known after apply)
      + cidr_block                                     = "192.168.3.0/24"
      + enable_dns64                                   = false
      + enable_resource_name_dns_a_record_on_launch    = false
      + enable_resource_name_dns_aaaa_record_on_launch = false
      + id                                             = (known after apply)
      + ipv6_cidr_block_association_id                 = (known after apply)
      + ipv6_native                                    = false
      + map_public_ip_on_launch                        = false
      + owner_id                                       = (known after apply)
      + private_dns_hostname_type_on_launch            = (known after apply)
      + tags                                           = {
          + "Environment" = "dev"
          + "Name"        = "public-subnet"
        }
      + tags_all                                       = {
          + "Environment" = "dev"
          + "Name"        = "public-subnet"
        }
      + vpc_id                                         = "vpc-0ff5212e9d1af6f7c"
    }

  # aws_subnet.main[4] will be created
  + resource "aws_subnet" "main" {
      + arn                                            = (known after apply)
      + assign_ipv6_address_on_creation                = false
      + availability_zone                              = "ap-northeast-2c"
      + availability_zone_id                           = (known after apply)
      + cidr_block                                     = "192.168.4.0/24"
      + enable_dns64                                   = false
      + enable_resource_name_dns_a_record_on_launch    = false
      + enable_resource_name_dns_aaaa_record_on_launch = false
      + id                                             = (known after apply)
      + ipv6_cidr_block_association_id                 = (known after apply)
      + ipv6_native                                    = false
      + map_public_ip_on_launch                        = false
      + owner_id                                       = (known after apply)
      + private_dns_hostname_type_on_launch            = (known after apply)
      + tags                                           = {
          + "Environment" = "dev"
          + "Name"        = "private-subnet"
        }
      + tags_all                                       = {
          + "Environment" = "dev"
          + "Name"        = "private-subnet"
        }
      + vpc_id                                         = "vpc-0ff5212e9d1af6f7c"
    }

 

이런 오류가 발생하는 이유는 count 반복문은 리소스의 배열로 저장되기 때문인데, 리소스를 식별할때 해당 배열의 인덱스를 사용하게 된다.

사진-26

 

즉, 새로 192.168.0.5 subnet을 생성 시 뒤 배열의 리소스(여기선 서브넷)들도 재 생성이 되며 프로비저닝이 된다. (그냥 없는 서브넷만 추가하는게 아님)

이는 for_each 반복문으로 해결이 가능한데, for_each은 map, set을 허용한다고 한다. 즉 key,value를 사용해서 해당 키와 값에 접근이 가능하여 삭제되고 추가되는 리소스에 대해 정확하게 지정해서 작업할 수 있을 듯 하다.

 

for_each에 대해서는 다음 포스팅으로 정리해보도록 하겠다.