インフラエンジニアの寺岡です。

AWS には「Amazon ECS」というサービスがあり、起動モードとして「Amazon EC2」と「AWS Fargate」の2種類が存在しています。

Fargate はコンテナの実行環境が AWS のフルマネージドで提供されているため、クラスタの管理が不要になるので大変便利ではあるのですが、その仕様上永続ボリュームをコンテナにマウントすることが出来ず、タスクの停止と同時にストレージも削除されてしまいます。

● Fargate タスクストレージ

今回検証した WordPress をコンテナで起動した場合、投稿した記事で利用している画像などは、全てローカルボリュームに保存されることになるため、ストレージが削除されてしまっては困ります。

それでも便利だから Fargate を使いたい、そんな方に朗報です。
Fargate のプラットフォームバージョン1.4から、EFS エンドポイントのサポートが開始されました。

● AWS Fargate がプラットフォームバージョン 1.4 をリリース

これであればコンテナ間でデータを共有しつつ、永続データを保持しておくことが出来そうです。
実際にやってみました。

今回検証した構成

今回の内容通りに構築していくと、最終的に以下のような構成になります。

構築は全て Terraform で行っているので、以下にコードを記載します。
Terraform のバージョンは「0.12.24」です。
参考になされる場合はご注意ください。

書いたコード

ディレクトリ構造は以下です。

$ tree
.
├── README.md
├── alb.tf
├── efs.tf
├── fargate.tf
├── iam.tf
├── provider.tf
├── rds.tf
├── roles
│   ├── fargate_task_assume_role.json
│   └── fargate_task_execution_policy.json
├── securitygroup.tf
├── ssm.tf
├── tasks
│   └── container_definitions.json
├── terraform.tfstate
├── terraform.tfstate.backup
├── variables.tf
└── vpc.tf

2 directories, 16 files

provider.tf

provider "aws" {
  access_key = var.access_key
  secret_key = var.secret_key
  region     = var.region

  assume_role {
    role_arn = var.role_arn
  }
}

variables.tf

####################
# Provider
####################
variable "access_key" {
  description = "AWS Access Key"
}

variable "secret_key" {
  description = "AWS Secret Key"
}

variable "role_arn" {
  description = "AWS Role Arn"
}

variable "region" {
  default = "ap-northeast-1"
}

vpc.tf

####################
# VPC
####################
resource "aws_vpc" "vpc" {
  cidr_block           = "10.0.0.0/16"
  enable_dns_support   = true
  enable_dns_hostnames = true

  tags = {
    Name = "vpc-fargate-efs"
  }
}

####################
# Subnet
####################
resource "aws_subnet" "public_1a" {
  vpc_id                  = aws_vpc.vpc.id
  availability_zone       = "${var.region}a"
  cidr_block              = "10.0.10.0/24"
  map_public_ip_on_launch = true

  tags = {
    Name = "subnet-fargate-efs-public-1a"
  }
}

resource "aws_subnet" "public_1c" {
  vpc_id                  = aws_vpc.vpc.id
  availability_zone       = "${var.region}c"
  cidr_block              = "10.0.11.0/24"
  map_public_ip_on_launch = true

  tags = {
    Name = "subnet-fargate-efs-public-1c"
  }
}

resource "aws_subnet" "dmz_1a" {
  vpc_id                  = aws_vpc.vpc.id
  availability_zone       = "${var.region}a"
  cidr_block              = "10.0.20.0/24"
  map_public_ip_on_launch = true

  tags = {
    Name = "subnet-fargate-efs-dmz-1a"
  }
}

resource "aws_subnet" "dmz_1c" {
  vpc_id                  = aws_vpc.vpc.id
  availability_zone       = "${var.region}c"
  cidr_block              = "10.0.21.0/24"
  map_public_ip_on_launch = true

  tags = {
    Name = "subnet-fargate-efs-dmz-1c"
  }
}

resource "aws_subnet" "private_1a" {
  vpc_id                  = aws_vpc.vpc.id
  availability_zone       = "${var.region}a"
  cidr_block              = "10.0.30.0/24"
  map_public_ip_on_launch = true

  tags = {
    Name = "subnet-fargate-efs-private-1a"
  }
}

resource "aws_subnet" "private_1c" {
  vpc_id                  = aws_vpc.vpc.id
  availability_zone       = "${var.region}c"
  cidr_block              = "10.0.31.0/24"
  map_public_ip_on_launch = true

  tags = {
    Name = "subnet-fargate-efs-private-1c"
  }
}

####################
# Route Table
####################
resource "aws_route_table" "public" {
  vpc_id = aws_vpc.vpc.id

  tags = {
    Name = "route-fargate-efs-public"
  }
}

resource "aws_route_table" "dmz" {
  vpc_id = aws_vpc.vpc.id

  tags = {
    Name = "route-fargate-efs-dmz"
  }
}

resource "aws_route_table" "private" {
  vpc_id = aws_vpc.vpc.id

  tags = {
    Name = "route-fargate-efs-private"
  }
}

####################
# IGW
####################
resource "aws_internet_gateway" "igw" {
  vpc_id = aws_vpc.vpc.id

  tags = {
    Name = "igw-fargate-efs"
  }
}

####################
# NATGW
####################
resource "aws_eip" "natgw" {
  vpc = true

  tags = {
    Name = "natgw-fargate-efs"
  }
}

resource "aws_nat_gateway" "natgw" {
  allocation_id = aws_eip.natgw.id
  subnet_id     = aws_subnet.public_1a.id

  tags = {
    Name = "natgw-fargate-efs"
  }

  depends_on = [aws_internet_gateway.igw]
}

####################
# Route
####################
resource "aws_route" "public" {
  route_table_id         = aws_route_table.public.id
  destination_cidr_block = "0.0.0.0/0"
  gateway_id             = aws_internet_gateway.igw.id
  depends_on             = [aws_route_table.public]
}

resource "aws_route" "dmz" {
  route_table_id         = aws_route_table.dmz.id
  destination_cidr_block = "0.0.0.0/0"
  nat_gateway_id         = aws_nat_gateway.natgw.id
  depends_on             = [aws_route_table.dmz]
}

####################
# Route Association
####################
resource "aws_route_table_association" "public_1a" {
  subnet_id      = aws_subnet.public_1a.id
  route_table_id = aws_route_table.public.id
}

resource "aws_route_table_association" "public_1c" {
  subnet_id      = aws_subnet.public_1c.id
  route_table_id = aws_route_table.public.id
}

resource "aws_route_table_association" "dmz_1a" {
  subnet_id      = aws_subnet.dmz_1a.id
  route_table_id = aws_route_table.dmz.id
}

resource "aws_route_table_association" "dmz_1c" {
  subnet_id      = aws_subnet.dmz_1c.id
  route_table_id = aws_route_table.dmz.id
}

resource "aws_route_table_association" "private_1a" {
  subnet_id      = aws_subnet.private_1a.id
  route_table_id = aws_route_table.private.id
}

resource "aws_route_table_association" "private_1c" {
  subnet_id      = aws_subnet.private_1c.id
  route_table_id = aws_route_table.private.id
}

securitygroup.tf

####################
# Security Group
####################
resource "aws_security_group" "alb" {
  name        = "alb-sg"
  description = "for ALB"
  vpc_id      = aws_vpc.vpc.id
}

resource "aws_security_group" "fargate" {
  name        = "fargate-sg"
  description = "for Fargate"
  vpc_id      = aws_vpc.vpc.id
}

resource "aws_security_group" "efs" {
  name        = "efs-sg"
  description = "for EFS"
  vpc_id      = aws_vpc.vpc.id
}

resource "aws_security_group" "rds" {
  name        = "rds-sg"
  description = "for RDS"
  vpc_id      = aws_vpc.vpc.id
}

#####################
# Security Group Rule
#####################
resource "aws_security_group_rule" "allow_http_for_alb" {
  security_group_id = aws_security_group.alb.id
  type              = "ingress"
  protocol          = "tcp"
  from_port         = 80
  to_port           = 80
  cidr_blocks       = ["0.0.0.0/0"]
  description       = "allow_http_for_alb"
}

resource "aws_security_group_rule" "from_alb_to_fargate" {
  security_group_id        = aws_security_group.fargate.id
  type                     = "ingress"
  protocol                 = "tcp"
  from_port                = 80
  to_port                  = 80
  source_security_group_id = aws_security_group.alb.id
  description              = "from_alb_to_fargate"
}

resource "aws_security_group_rule" "from_fargate_to_efs" {
  security_group_id        = aws_security_group.efs.id
  type                     = "ingress"
  protocol                 = "tcp"
  from_port                = 2049
  to_port                  = 2049
  source_security_group_id = aws_security_group.fargate.id
  description              = "from_fargate_to_efs"
}

resource "aws_security_group_rule" "from_fargate_to_rds" {
  security_group_id        = aws_security_group.rds.id
  type                     = "ingress"
  protocol                 = "tcp"
  from_port                = 3306
  to_port                  = 3306
  source_security_group_id = aws_security_group.fargate.id
  description              = "from_fargate_to_rds"
}

resource "aws_security_group_rule" "egress_alb" {
  security_group_id = aws_security_group.alb.id
  type              = "egress"
  protocol          = "-1"
  from_port         = 0
  to_port           = 0
  cidr_blocks       = ["0.0.0.0/0"]
  description       = "Outbound ALL"
}

resource "aws_security_group_rule" "egress_fargate" {
  security_group_id = aws_security_group.fargate.id
  type              = "egress"
  protocol          = "-1"
  from_port         = 0
  to_port           = 0
  cidr_blocks       = ["0.0.0.0/0"]
  description       = "Outbound ALL"
}

resource "aws_security_group_rule" "egress_efs" {
  security_group_id = aws_security_group.efs.id
  type              = "egress"
  protocol          = "-1"
  from_port         = 0
  to_port           = 0
  cidr_blocks       = ["0.0.0.0/0"]
  description       = "Outbound ALL"
}

resource "aws_security_group_rule" "egress_rds" {
  security_group_id = aws_security_group.rds.id
  type              = "egress"
  protocol          = "-1"
  from_port         = 0
  to_port           = 0
  cidr_blocks       = ["0.0.0.0/0"]
  description       = "Outbound ALL"
}

alb.tf

####################
# ALB
####################
resource "aws_lb" "alb" {
  name               = "alb-fargate-efs"
  internal           = false
  load_balancer_type = "application"
  security_groups = [
    aws_security_group.alb.id
  ]
  subnets = [
    aws_subnet.public_1a.id,
    aws_subnet.public_1c.id
  ]
}

####################
# Target Group
####################
resource "aws_lb_target_group" "alb" {
  name                 = "fargate-efs-tg"
  port                 = "80"
  protocol             = "HTTP"
  target_type          = "ip"
  vpc_id               = aws_vpc.vpc.id
  deregistration_delay = "60"

  health_check {
    interval            = "10"
    path                = "/"
    port                = "traffic-port"
    protocol            = "HTTP"
    timeout             = "4"
    healthy_threshold   = "2"
    unhealthy_threshold = "10"
    matcher             = "200-302"
  }
}

####################
# Listener
####################
resource "aws_lb_listener" "alb" {
  load_balancer_arn = aws_lb.alb.arn
  port              = "80"
  protocol          = "HTTP"

  default_action {
    type             = "forward"
    target_group_arn = aws_lb_target_group.alb.arn
  }
}

efs.tf

####################
# EFS
####################
resource "aws_efs_file_system" "efs" {
  creation_token                  = "fargate-efs"
  provisioned_throughput_in_mibps = "50"
  throughput_mode                 = "provisioned"

  tags = {
    Name = "fargate-efs"
  }
}

####################
# Mount Target
####################
resource "aws_efs_mount_target" "dmz_1a" {
  file_system_id = aws_efs_file_system.efs.id
  subnet_id      = aws_subnet.dmz_1a.id
  security_groups = [
    aws_security_group.efs.id
  ]
}

resource "aws_efs_mount_target" "dmz_1c" {
  file_system_id = aws_efs_file_system.efs.id
  subnet_id      = aws_subnet.dmz_1c.id
  security_groups = [
    aws_security_group.efs.id
  ]
}

rds.tf

####################
# Parameter Group
####################
resource "aws_db_parameter_group" "rds" {
  name        = "fargate-efs-pg"
  family      = "mysql5.7"
  description = "for RDS"
}

####################
# Subnet Group
####################
resource "aws_db_subnet_group" "rds" {
  name        = "fargate-efs-sg"
  description = "for RDS"
  subnet_ids = [
    aws_subnet.private_1a.id,
    aws_subnet.private_1c.id
  ]
}

####################
# Instance
####################
resource "aws_db_instance" "rds" {
  identifier                = "fargate-efs-db01"
  engine                    = "mysql"
  engine_version            = "5.7"
  instance_class            = "db.t3.micro"
  storage_type              = "gp2"
  allocated_storage         = "50"
  max_allocated_storage     = "100"
  username                  = "root"
  password                  = "password"
  final_snapshot_identifier = "fargate-efs-db01-final"
  db_subnet_group_name      = aws_db_subnet_group.rds.name
  parameter_group_name      = aws_db_parameter_group.rds.name
  multi_az                  = false
  vpc_security_group_ids = [
    aws_security_group.rds.id
  ]
  backup_retention_period = "7"
  apply_immediately       = true
}

fargate.tf

####################
# Cluster
####################
resource "aws_ecs_cluster" "cluster" {
  name = "cluster-fargate-efs"

  setting {
    name  = "containerInsights"
    value = "disabled"
  }
}

####################
# Task Definition
####################
resource "aws_ecs_task_definition" "task" {
  family                = "task-fargate-wordpress"
  container_definitions = file("tasks/container_definitions.json")
  cpu                   = "256"
  memory                = "512"
  network_mode          = "awsvpc"
  execution_role_arn    = aws_iam_role.fargate_task_execution.arn

  volume {
    name = "fargate-efs"

    efs_volume_configuration {
      file_system_id = aws_efs_file_system.efs.id
      root_directory = "/"
    }
  }

  requires_compatibilities = [
    "FARGATE"
  ]
}

####################
# Service
####################
resource "aws_ecs_service" "service" {
  name             = "service-fargate-efs"
  cluster          = aws_ecs_cluster.cluster.arn
  task_definition  = aws_ecs_task_definition.task.arn
  desired_count    = 2
  launch_type      = "FARGATE"
  platform_version = "1.4.0"

  load_balancer {
    target_group_arn = aws_lb_target_group.alb.arn
    container_name   = "wordpress"
    container_port   = "80"
  }

  network_configuration {
    subnets = [
      aws_subnet.dmz_1a.id,
      aws_subnet.dmz_1c.id
    ]
    security_groups = [
      aws_security_group.fargate.id
    ]
    assign_public_ip = false
  }
}

container_definition.json

[
    {
        "name": "wordpress",
        "image": "wordpress:latest",
        "essential": true,
        "portMappings": [
            {
                "containerPort": 80,
                "hostPort": 80
            }
        ],
        "mountPoints": [
            {
                "containerPath": "/var/www/html",
                "sourceVolume": "fargate-efs"
            }
        ],
        "secrets": [
            {
                "name": "WORDPRESS_DB_HOST",
                "valueFrom": "WORDPRESS_DB_HOST"
            },
            {
                "name": "WORDPRESS_DB_USER",
                "valueFrom": "WORDPRESS_DB_USER"
            },
            {
                "name": "WORDPRESS_DB_PASSWORD",
                "valueFrom": "WORDPRESS_DB_PASSWORD"
            },
            {
                "name": "WORDPRESS_DB_NAME",
                "valueFrom": "WORDPRESS_DB_NAME"
            }
        ]
    }
]

iam.tf

####################
# IAM Role
####################
resource "aws_iam_role" "fargate_task_execution" {
  name               = "role-fargate_task_execution"
  assume_role_policy = file("./roles/fargate_task_assume_role.json")
}

####################
# IAM Role Policy
####################
resource "aws_iam_role_policy" "fargate_task_execution" {
  name   = "execution-policy"
  role   = aws_iam_role.fargate_task_execution.name
  policy = file("./roles/fargate_task_execution_policy.json")
}

fargate_task_assume_role.json

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Principal": {
                "Service": "ecs-tasks.amazonaws.com"
            },
            "Action": "sts:AssumeRole"
        }
    ]
}

fargate_task_execution_policy.json

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": "ssm:GetParameters",
            "Resource": "*"
        }
    ]
}

ssm.tf

####################
# Parameter
####################
resource "aws_ssm_parameter" "wordpress_db_host" {
  name        = "WORDPRESS_DB_HOST"
  description = "WORDPRESS_DB_HOST"
  type        = "String"
  value       = aws_db_instance.rds.address
}

resource "aws_ssm_parameter" "wordpress_db_user" {
  name        = "WORDPRESS_DB_USER"
  description = "WORDPRESS_DB_USER"
  type        = "String"
  value       = "wordpress"
}

resource "aws_ssm_parameter" "wordpress_db_password" {
  name        = "WORDPRESS_DB_PASSWORD"
  description = "WORDPRESS_DB_PASSWORD"
  type        = "String"
  value       = "password"
}

resource "aws_ssm_parameter" "wordpress_db_name" {
  name        = "WORDPRESS_DB_NAME"
  description = "WORDPRESS_DB_NAME"
  type        = "String"
  value       = "wordpress"
}

RDS の初期設定

WordPress 用にデータベースとユーザーを作成しておきましょう。

$ create database wordpress;
$ CREATE USER 'wordpress'@'%' IDENTIFIED WITH mysql_native_password BY 'password';
$ grant all privileges on wordpress.* to wordpress@'%';

動作確認

terraform apply を実行した後に、Fargate のタスクが2つ立ち上がるので、ALB のエンドポイントにアクセスします。

WordPressの画面が表示されるので、初期設定を行うと以下のようにサイトが表示されました。
ここまではまだ問題にはならないですね。

ここからが本題、画像付きの記事を管理画面から投稿してみます。

投稿ボタンを押したら記事のページに遷移して、ひたすらF5キーを連打して更新してみます。

EFS が正しく認識されていない場合画面のリロードによって、画像が表示されるとき・されないときが起こり得るのですが、100回くらい無心で画面をリロードしたところ、特に表示が崩れることはありませんでしたので大丈夫そうです。

まとめ

Fargate と EFS の連携が可能になったことで、構築する際の設計の幅が大きく広がりました。
プラットフォームバージョン1.4では、その他にも便利なアップデートが数多くあるので、皆様も一度ご利用されてみてはいかがでしょうか。