로드 밸런서

# /etc/haproxy/haproxy.cfg - HAProxy 로드 밸런서 설정

global
    log /dev/log local0
    maxconn 50000
    daemon

defaults
    log     global
    mode    http
    option  httplog
    option  dontlognull
    timeout connect 5s
    timeout client  30s
    timeout server  30s
    retries 3

# 프론트엔드 (트래픽 수신)
frontend http_front
    bind *:80
    bind *:443 ssl crt /etc/ssl/certs/example.pem

    # ACL 정의 (L7 라우팅 규칙)
    acl is_api path_beg /api
    acl is_static path_beg /static
    acl is_websocket hdr(Upgrade) -i websocket

    # ACL 기반 백엔드 라우팅
    use_backend api_backend if is_api
    use_backend static_backend if is_static
    use_backend websocket_backend if is_websocket
    default_backend web_backend

# 웹 백엔드 (Round Robin)
backend web_backend
    balance roundrobin
    option httpchk GET /health HTTP/1.1\r\nHost:\ localhost

    # Health Check: 2초 간격, 3번 실패시 제외
    server web1 10.0.1.10:8080 check inter 2s fall 3 rise 2 weight 5
    server web2 10.0.1.11:8080 check inter 2s fall 3 rise 2 weight 3
    server web3 10.0.1.12:8080 check inter 2s fall 3 rise 2 weight 2

# API 백엔드 (Least Connections)
backend api_backend
    balance leastconn
    option httpchk GET /api/health

    # 쿠키 기반 세션 스티키니스
    cookie SERVERID insert indirect nocache
    server api1 10.0.2.10:3000 check cookie api1
    server api2 10.0.2.11:3000 check cookie api2

# 정적 파일 백엔드
backend static_backend
    balance roundrobin
    server static1 10.0.3.10:80 check
    server static2 10.0.3.11:80 check

# WebSocket 백엔드
backend websocket_backend
    balance source
    timeout tunnel 3600s
    server ws1 10.0.4.10:8080 check
    server ws2 10.0.4.11:8080 check

# 모니터링 페이지
listen stats
    bind *:8404
    stats enable
    stats uri /stats
    stats auth admin:password123

// AWS CDK - ALB + NLB 로드 밸런서 설정
import * as cdk from 'aws-cdk-lib';
import * as ec2 from 'aws-cdk-lib/aws-ec2';
import * as ecs from 'aws-cdk-lib/aws-ecs';
import * as elbv2 from 'aws-cdk-lib/aws-elasticloadbalancingv2';

export class LoadBalancerStack extends cdk.Stack {
  constructor(scope: cdk.App, id: string) {
    super(scope, id);

    const vpc = new ec2.Vpc(this, 'VPC', { maxAzs: 3 });

    // ═══════════════════════════════════════
    // ALB (Application Load Balancer) - L7
    // ═══════════════════════════════════════
    const alb = new elbv2.ApplicationLoadBalancer(this, 'ALB', {
      vpc,
      internetFacing: true,
      loadBalancerName: 'my-alb',
    });

    // HTTPS 리스너 (SSL Termination)
    const httpsListener = alb.addListener('HTTPS', {
      port: 443,
      certificates: [certificate],
      sslPolicy: elbv2.SslPolicy.TLS12,
    });

    // 타겟 그룹 (백엔드 서버)
    const webTargetGroup = new elbv2.ApplicationTargetGroup(this, 'WebTG', {
      vpc,
      port: 8080,
      protocol: elbv2.ApplicationProtocol.HTTP,
      targetType: elbv2.TargetType.IP,
      // Health Check 설정
      healthCheck: {
        path: '/health',
        interval: cdk.Duration.seconds(30),
        timeout: cdk.Duration.seconds(5),
        healthyThresholdCount: 2,
        unhealthyThresholdCount: 3,
        healthyHttpCodes: '200-299',
      },
      // 로드 밸런싱 알고리즘
      loadBalancingAlgorithmType:
        elbv2.TargetGroupLoadBalancingAlgorithmType.LEAST_OUTSTANDING_REQUESTS,
      // 스티키 세션 (선택적)
      stickinessCookieDuration: cdk.Duration.hours(1),
    });

    // URL 기반 라우팅 (L7 기능)
    httpsListener.addTargetGroups('Default', {
      targetGroups: [webTargetGroup],
    });

    // /api/* 요청은 API 서버로 라우팅
    httpsListener.addTargetGroups('ApiRouting', {
      priority: 10,
      conditions: [elbv2.ListenerCondition.pathPatterns(['/api/*'])],
      targetGroups: [apiTargetGroup],
    });

    // ═══════════════════════════════════════
    // NLB (Network Load Balancer) - L4
    // ═══════════════════════════════════════
    const nlb = new elbv2.NetworkLoadBalancer(this, 'NLB', {
      vpc,
      internetFacing: true,
      crossZoneEnabled: true, // 교차 영역 로드 밸런싱
    });

    // TCP 리스너 (L4)
    const tcpListener = nlb.addListener('TCP', {
      port: 443,
    });

    // 타겟 그룹 (게임 서버 등)
    const gameTargetGroup = new elbv2.NetworkTargetGroup(this, 'GameTG', {
      vpc,
      port: 7777,
      protocol: elbv2.Protocol.TCP,
      healthCheck: {
        protocol: elbv2.Protocol.TCP,
        interval: cdk.Duration.seconds(10),
      },
      // 클라이언트 IP 보존
      preserveClientIp: true,
    });

    tcpListener.addTargetGroups('GameServers', gameTargetGroup);

    // 출력
    new cdk.CfnOutput(this, 'ALBDnsName', { value: alb.loadBalancerDnsName });
    new cdk.CfnOutput(this, 'NLBDnsName', { value: nlb.loadBalancerDnsName });
  }
}