ALBの加重ルーティングでカナリアリリースを設計する方法｜ターゲットグループ重み付けでAWS本番環境のトラフィックを段階移行する実践パターン

この記事のポイント

・ALBの加重ルーティングはターゲットグループに0～999の重みを付けて実現する
・aws elbv2 modify-ruleで重みをリアルタイムに変更できるため再デプロイ不要
・マルチAZ環境ではCross-Zone Load Balancingの動作確認と各AZへの均等登録が重要
・問題発生時は重みを0/100に戻すだけで即座にロールバックが完了する

# create the Blue target group (current version)
$ aws elbv2 create-target-group \
  --name app-blue \
  --protocol HTTP \
  --port 8080 \
  --vpc-id vpc-0a1b2c3d4e5f6a7b8 \
  --health-check-path /health \
  --health-check-interval-seconds 15 \
  --healthy-threshold-count 2 \
  --region ap-northeast-1

{
    "TargetGroups": [
        {
            "TargetGroupArn": "arn:aws:elasticloadbalancing:ap-northeast-1:123456789012:targetgroup/app-blue/1234567890abcdef",
            "TargetGroupName": "app-blue",
            "Protocol": "HTTP",
            "Port": 8080,
            "VpcId": "vpc-0a1b2c3d4e5f6a7b8",
            "HealthCheckProtocol": "HTTP",
            "HealthCheckPath": "/health",
            "HealthCheckIntervalSeconds": 15,
            "HealthyThresholdCount": 2
        }
    ]
}

# BlueターゲットグループにEC2インスタンスを登録する
$ aws elbv2 register-targets \
  --target-group-arn arn:aws:elasticloadbalancing:ap-northeast-1:123456789012:targetgroup/app-blue/1234567890abcdef \
  --targets Id=i-0a1b2c3d4e5f6a7b8 Id=i-0b2c3d4e5f6a7b8c9 \
  --region ap-northeast-1

# GreenターゲットグループをAWS CLIで作成する
$ aws elbv2 create-target-group \
  --name app-green \
  --protocol HTTP \
  --port 8080 \
  --vpc-id vpc-0a1b2c3d4e5f6a7b8 \
  --health-check-path /health \
  --health-check-interval-seconds 15 \
  --healthy-threshold-count 2 \
  --region ap-northeast-1

{
    "TargetGroups": [
        {
            "TargetGroupArn": "arn:aws:elasticloadbalancing:ap-northeast-1:123456789012:targetgroup/app-green/fedcba0987654321",
            "TargetGroupName": "app-green",
            "Protocol": "HTTP",
            "Port": 8080,
            "VpcId": "vpc-0a1b2c3d4e5f6a7b8",
            "HealthCheckProtocol": "HTTP",
            "HealthCheckPath": "/health",
            "HealthCheckIntervalSeconds": 15,
            "HealthyThresholdCount": 2
        }
    ]
}

# ALBのリスナー一覧を確認する
$ aws elbv2 describe-listeners \
  --load-balancer-arn arn:aws:elasticloadbalancing:ap-northeast-1:123456789012:loadbalancer/app/prod-alb/a1b2c3d4e5f6a7b8 \
  --region ap-northeast-1 \
  --query 'Listeners[*].[ListenerArn,Protocol,Port]' \
  --output table

-----------------------------------------------------------------------------------------------------------
|                                          DescribeListeners                                              |
+---------------------------------------------------------------------------------------------+----------+-----+
|  arn:aws:elasticloadbalancing:ap-northeast-1:123456789012:listener/app/prod-alb/a1b2c.../a | HTTPS    | 443 |
+---------------------------------------------------------------------------------------------+----------+-----+

# デフォルトルールのARNを確認する
$ aws elbv2 describe-rules \
  --listener-arn arn:aws:elasticloadbalancing:ap-northeast-1:123456789012:listener/app/prod-alb/a1b2c3d4e5f6a7b8/f0a1b2c3d4e5f6a7 \
  --query 'Rules[?IsDefault==`true`].RuleArn' \
  --output text \
  --region ap-northeast-1

arn:aws:elasticloadbalancing:ap-northeast-1:123456789012:listener-rule/app/prod-alb/a1b2c3d4e5f6a7b8/f0a1b2c3d4e5f6a7/1234abcd5678efgh

# デフォルトルールに加重ルーティングを設定する（Blue:90、Green:10）
$ aws elbv2 modify-rule \
  --rule-arn arn:aws:elasticloadbalancing:ap-northeast-1:123456789012:listener-rule/app/prod-alb/a1b2c3d4e5f6a7b8/f0a1b2c3d4e5f6a7/1234abcd5678efgh \
  --actions '[
    {
      "Type": "forward",
      "ForwardConfig": {
        "TargetGroups": [
          {
            "TargetGroupArn": "arn:aws:elasticloadbalancing:ap-northeast-1:123456789012:targetgroup/app-blue/1234567890abcdef",
            "Weight": 90
          },
          {
            "TargetGroupArn": "arn:aws:elasticloadbalancing:ap-northeast-1:123456789012:targetgroup/app-green/fedcba0987654321",
            "Weight": 10
          }
        ]
      }
    }
  ]' \
  --region ap-northeast-1

# Blue:50、Green:50 に変更する
$ aws elbv2 modify-rule \
  --rule-arn arn:aws:elasticloadbalancing:ap-northeast-1:123456789012:listener-rule/app/prod-alb/a1b2c3d4e5f6a7b8/f0a1b2c3d4e5f6a7/1234abcd5678efgh \
  --actions '[
    {
      "Type": "forward",
      "ForwardConfig": {
        "TargetGroups": [
          {
            "TargetGroupArn": "arn:aws:elasticloadbalancing:ap-northeast-1:123456789012:targetgroup/app-blue/1234567890abcdef",
            "Weight": 50
          },
          {
            "TargetGroupArn": "arn:aws:elasticloadbalancing:ap-northeast-1:123456789012:targetgroup/app-green/fedcba0987654321",
            "Weight": 50
          }
        ]
      }
    }
  ]' \
  --region ap-northeast-1

# Blue:0、Green:100 で完全移行する
$ aws elbv2 modify-rule \
  --rule-arn arn:aws:elasticloadbalancing:ap-northeast-1:123456789012:listener-rule/app/prod-alb/a1b2c3d4e5f6a7b8/f0a1b2c3d4e5f6a7/1234abcd5678efgh \
  --actions '[
    {
      "Type": "forward",
      "ForwardConfig": {
        "TargetGroups": [
          {
            "TargetGroupArn": "arn:aws:elasticloadbalancing:ap-northeast-1:123456789012:targetgroup/app-blue/1234567890abcdef",
            "Weight": 0
          },
          {
            "TargetGroupArn": "arn:aws:elasticloadbalancing:ap-northeast-1:123456789012:targetgroup/app-green/fedcba0987654321",
            "Weight": 100
          }
        ]
      }
    }
  ]' \
  --region ap-northeast-1

# 緊急ロールバック：Blue:100、Green:0 に戻す
$ aws elbv2 modify-rule \
  --rule-arn arn:aws:elasticloadbalancing:ap-northeast-1:123456789012:listener-rule/app/prod-alb/a1b2c3d4e5f6a7b8/f0a1b2c3d4e5f6a7/1234abcd5678efgh \
  --actions '[
    {
      "Type": "forward",
      "ForwardConfig": {
        "TargetGroups": [
          {
            "TargetGroupArn": "arn:aws:elasticloadbalancing:ap-northeast-1:123456789012:targetgroup/app-blue/1234567890abcdef",
            "Weight": 100
          },
          {
            "TargetGroupArn": "arn:aws:elasticloadbalancing:ap-northeast-1:123456789012:targetgroup/app-green/fedcba0987654321",
            "Weight": 0
          }
        ]
      }
    }
  ]' \
  --region ap-northeast-1

# ALBのCross-Zone Load Balancing設定を確認する
$ aws elbv2 describe-load-balancer-attributes \
  --load-balancer-arn arn:aws:elasticloadbalancing:ap-northeast-1:123456789012:loadbalancer/app/prod-alb/a1b2c3d4e5f6a7b8 \
  --query 'Attributes[?Key==`load_balancing.cross_zone.enabled`]' \
  --output table \
  --region ap-northeast-1

-----------------------------------
|  DescribeLoadBalancerAttributes |
+-------------------------------------+-------+
|  Key                                | Value |
+-------------------------------------+-------+
|  load_balancing.cross_zone.enabled  | true  |
+-------------------------------------+-------+