Split View: API Gateway 완전 가이드 2025: Kong, Envoy, AWS API Gateway, 인증/레이트리밋/모니터링

API Gateway 없는 세계:

  [클라이언트]
     │  │  │
     │  │  └──── [서비스 A] (자체 인증, 자체 로깅, 자체 레이트 리밋)
     │  └─────── [서비스 B] (자체 인증, 자체 로깅, 자체 레이트 리밋)
     └────────── [서비스 C] (자체 인증, 자체 로깅, 자체 레이트 리밋)
                                     ↑
                              중복! 불일치! 관리 불가!

API Gateway가 있는 세계:

  [클라이언트]
       │
  ┌────┴─────────────────────────┐
  │        API Gateway            │
  │  ┌─────────────────────────┐ │
  │  │ 인증 / 인가             │ │
  │  │ 레이트 리밋             │ │
  │  │ 요청 변환               │ │
  │  │ 캐싱                    │ │
  │  │ 로깅 / 모니터링         │ │
  │  │ 서킷 브레이커            │ │
  │  │ 로드 밸런싱             │ │
  │  └─────────────────────────┘ │
  └──────┬───────┬───────┬───────┘
         │       │       │
      [서비스A] [서비스B] [서비스C]
      (비즈니스  (비즈니스  (비즈니스
       로직만)    로직만)    로직만)

3가지 핵심 Gateway 패턴:

1. Routing Pattern (라우팅)
   클라이언트 요청을 올바른 백엔드 서비스로 전달
   /api/users  →  User Service
   /api/orders →  Order Service
   /api/products → Product Service

2. Aggregation Pattern (집약)
   여러 서비스의 응답을 하나로 합쳐서 반환
   GET /api/dashboard →
     User Service (프로필) +
     Order Service (최근 주문) +
     Notification Service (알림)
   → 단일 JSON 응답

3. Offloading Pattern (오프로딩)
   공통 기능을 서비스에서 Gateway로 이전
   인증, SSL 종료, 압축, 캐싱, CORS 등
   → 서비스는 비즈니스 로직에만 집중

Kong Architecture:

  [클라이언트]
       │
  ┌────┴────────────────────────────────┐
  │           Kong Gateway               │
  │                                      │
  │  ┌──────────────────────────────┐   │
  │  │     Kong Core (OpenResty)     │   │
  │  │     Nginx + LuaJIT            │   │
  │  └──────────┬───────────────────┘   │
  │             │                        │
  │  ┌──────────┴───────────────────┐   │
  │  │        Plugin Layer           │   │
  │  │                               │   │
  │  │  Auth │ Rate  │ Logging │ ... │   │
  │  │       │ Limit │         │     │   │
  │  └──────────────────────────────┘   │
  │             │                        │
  │  ┌──────────┴───────────────────┐   │
  │  │      Data Store               │   │
  │  │  PostgreSQL │ Cassandra       │   │
  │  │  (또는 DB-less Mode)          │   │
  │  └──────────────────────────────┘   │
  └──────┬──────────┬──────────┬────────┘
         │          │          │
    [Service A] [Service B] [Service C]

# kong.yml - DB-less Declarative Configuration
_format_version: "3.0"
_transform: true

services:
  - name: user-service
    url: http://user-service:8080
    routes:
      - name: user-routes
        paths:
          - /api/v1/users
        methods:
          - GET
          - POST
          - PUT
          - DELETE
        strip_path: false
    plugins:
      - name: rate-limiting
        config:
          minute: 100
          hour: 5000
          policy: local
      - name: jwt
        config:
          uri_param_names:
            - token
          claims_to_verify:
            - exp

  - name: order-service
    url: http://order-service:8080
    routes:
      - name: order-routes
        paths:
          - /api/v1/orders
        strip_path: false
    plugins:
      - name: rate-limiting
        config:
          minute: 50
          hour: 2000
      - name: request-transformer
        config:
          add:
            headers:
              - "X-Request-Source:api-gateway"
              - "X-Forwarded-Service:order-service"

  - name: product-service
    url: http://product-service:8080
    routes:
      - name: product-routes
        paths:
          - /api/v1/products
        strip_path: false
    plugins:
      - name: proxy-cache
        config:
          response_code:
            - 200
          request_method:
            - GET
          content_type:
            - "application/json"
          cache_ttl: 300
          strategy: memory

# Global Plugins
plugins:
  - name: correlation-id
    config:
      header_name: X-Request-ID
      generator: uuid
      echo_downstream: true
  - name: prometheus
    config:
      per_consumer: true
  - name: file-log
    config:
      path: /dev/stdout
      reopen: true

Kong Plugin 카테고리:

Authentication:
├── jwt           - JWT 토큰 검증
├── oauth2        - OAuth2 서버 내장
├── key-auth      - API Key 인증
├── basic-auth    - Basic 인증
├── hmac-auth     - HMAC 서명 인증
├── ldap-auth     - LDAP/AD 인증
└── openid-connect - OIDC (Enterprise)

Security:
├── cors          - Cross-Origin 정책
├── ip-restriction - IP 화이트/블랙리스트
├── bot-detection  - 봇 탐지
├── acl           - Access Control Lists
└── mtls-auth     - mTLS 인증

Traffic Control:
├── rate-limiting       - 레이트 리밋
├── request-size-limiting - 요청 크기 제한
├── request-termination   - 요청 차단/유지보수 모드
└── proxy-cache          - 응답 캐싱

Transformations:
├── request-transformer   - 요청 헤더/바디 변환
├── response-transformer  - 응답 헤더/바디 변환
├── correlation-id        - 요청 추적 ID
└── grpc-gateway          - REST to gRPC 변환

Observability:
├── prometheus    - Prometheus 메트릭
├── datadog       - Datadog APM 통합
├── zipkin        - 분산 트레이싱
├── file-log      - 파일 로깅
├── http-log      - HTTP 기반 로그 전송
└── opentelemetry - OTel 통합

-- custom-auth-plugin/handler.lua
local BasePlugin = require "kong.plugins.base_plugin"
local CustomAuthHandler = BasePlugin:extend()

CustomAuthHandler.VERSION = "1.0.0"
CustomAuthHandler.PRIORITY = 1000  -- 실행 순서

function CustomAuthHandler:new()
  CustomAuthHandler.super.new(self, "custom-auth")
end

function CustomAuthHandler:access(conf)
  CustomAuthHandler.super.access(self)

  -- 1. API Key 추출
  local api_key = kong.request.get_header("X-API-Key")
  if not api_key then
    return kong.response.exit(401, {
      message = "Missing API Key"
    })
  end

  -- 2. 외부 인증 서비스 호출
  local httpc = require("resty.http").new()
  local res, err = httpc:request_uri(conf.auth_service_url, {
    method = "POST",
    headers = {
      ["Content-Type"] = "application/json",
    },
    body = '{"api_key":"' .. api_key .. '"}',
    timeout = conf.timeout or 5000,
  })

  if not res then
    kong.log.err("Auth service error: ", err)
    return kong.response.exit(503, {
      message = "Auth service unavailable"
    })
  end

  if res.status ~= 200 then
    return kong.response.exit(403, {
      message = "Invalid API Key"
    })
  end

  -- 3. 인증 정보를 업스트림 헤더에 추가
  local cjson = require "cjson.safe"
  local body = cjson.decode(res.body)
  if body then
    kong.service.request.set_header("X-Consumer-ID", body.consumer_id or "")
    kong.service.request.set_header("X-Consumer-Plan", body.plan or "free")
  end
end

return CustomAuthHandler

-- custom-auth-plugin/schema.lua
local typedefs = require "kong.db.schema.typedefs"

return {
  name = "custom-auth",
  fields = {
    { consumer = typedefs.no_consumer },
    { protocols = typedefs.protocols_http },
    { config = {
        type = "record",
        fields = {
          { auth_service_url = {
              type = "string",
              required = true,
              default = "http://auth-service:8080/validate"
          }},
          { timeout = {
              type = "number",
              default = 5000
          }},
          { cache_ttl = {
              type = "number",
              default = 60
          }},
        },
    }},
  },
}

Envoy Core Architecture:

  ┌──────────────────────────────────────────────┐
  │              Envoy Proxy                      │
  │                                               │
  │  Listener (포트 바인딩)                       │
  │    │                                          │
  │    ▼                                          │
  │  Filter Chain (필터 체인)                     │
  │    ├── Network Filters (L3/L4)               │
  │    │     ├── TCP Proxy                        │
  │    │     ├── TLS Inspector                    │
  │    │     └── HTTP Connection Manager          │
  │    │                                          │
  │    └── HTTP Filters (L7)                     │
  │          ├── Router (라우팅)                  │
  │          ├── CORS                             │
  │          ├── JWT Auth                         │
  │          ├── Rate Limit                       │
  │          ├── WASM Filter (커스텀)             │
  │          └── ...                              │
  │                                               │
  │  Route Configuration                          │
  │    │                                          │
  │    ▼                                          │
  │  Cluster (업스트림 서비스 그룹)               │
  │    ├── Endpoint Discovery                     │
  │    ├── Load Balancing                         │
  │    ├── Health Checking                        │
  │    ├── Circuit Breaking                       │
  │    └── Outlier Detection                      │
  └──────────────────────────────────────────────┘

# envoy.yaml - Static Configuration
static_resources:
  listeners:
    - name: main_listener
      address:
        socket_address:
          address: 0.0.0.0
          port_value: 8080
      filter_chains:
        - filters:
            - name: envoy.filters.network.http_connection_manager
              typed_config:
                "@type": type.googleapis.com/envoy.extensions.filters.network.http_connection_manager.v3.HttpConnectionManager
                stat_prefix: ingress_http
                codec_type: AUTO
                access_log:
                  - name: envoy.access_loggers.stdout
                    typed_config:
                      "@type": type.googleapis.com/envoy.extensions.access_loggers.stream.v3.StdoutAccessLog
                      log_format:
                        json_format:
                          timestamp: "%START_TIME%"
                          method: "%REQ(:METHOD)%"
                          path: "%REQ(X-ENVOY-ORIGINAL-PATH?:PATH)%"
                          status: "%RESPONSE_CODE%"
                          duration: "%DURATION%"
                          upstream: "%UPSTREAM_HOST%"
                          request_id: "%REQ(X-REQUEST-ID)%"
                route_config:
                  name: local_route
                  virtual_hosts:
                    - name: api_service
                      domains: ["*"]
                      routes:
                        # User Service Routes
                        - match:
                            prefix: "/api/v1/users"
                          route:
                            cluster: user_service
                            timeout: 10s
                            retry_policy:
                              retry_on: "5xx,connect-failure"
                              num_retries: 3
                              per_try_timeout: 3s
                        # Order Service Routes
                        - match:
                            prefix: "/api/v1/orders"
                          route:
                            cluster: order_service
                            timeout: 15s
                        # Product Service (with canary)
                        - match:
                            prefix: "/api/v1/products"
                          route:
                            weighted_clusters:
                              clusters:
                                - name: product_service_v1
                                  weight: 90
                                - name: product_service_v2
                                  weight: 10
                http_filters:
                  - name: envoy.filters.http.cors
                    typed_config:
                      "@type": type.googleapis.com/envoy.extensions.filters.http.cors.v3.Cors
                  - name: envoy.filters.http.jwt_authn
                    typed_config:
                      "@type": type.googleapis.com/envoy.extensions.filters.http.jwt_authn.v3.JwtAuthentication
                      providers:
                        auth0:
                          issuer: "https://company.auth0.com/"
                          audiences:
                            - "https://api.company.com"
                          remote_jwks:
                            http_uri:
                              uri: "https://company.auth0.com/.well-known/jwks.json"
                              cluster: auth0_jwks
                              timeout: 5s
                            cache_duration: 600s
                      rules:
                        - match:
                            prefix: "/api/"
                          requires:
                            provider_name: "auth0"
                  - name: envoy.filters.http.router
                    typed_config:
                      "@type": type.googleapis.com/envoy.extensions.filters.http.router.v3.Router

  clusters:
    - name: user_service
      connect_timeout: 5s
      type: STRICT_DNS
      lb_policy: ROUND_ROBIN
      health_checks:
        - timeout: 3s
          interval: 10s
          unhealthy_threshold: 3
          healthy_threshold: 2
          http_health_check:
            path: "/health"
      circuit_breakers:
        thresholds:
          - priority: DEFAULT
            max_connections: 1024
            max_pending_requests: 1024
            max_requests: 1024
            max_retries: 3
      load_assignment:
        cluster_name: user_service
        endpoints:
          - lb_endpoints:
              - endpoint:
                  address:
                    socket_address:
                      address: user-service
                      port_value: 8080

    - name: order_service
      connect_timeout: 5s
      type: STRICT_DNS
      lb_policy: LEAST_REQUEST
      outlier_detection:
        consecutive_5xx: 5
        interval: 10s
        base_ejection_time: 30s
        max_ejection_percent: 50
      load_assignment:
        cluster_name: order_service
        endpoints:
          - lb_endpoints:
              - endpoint:
                  address:
                    socket_address:
                      address: order-service
                      port_value: 8080

xDS API 종류:

  ┌──────────────────────────────────────┐
  │          Control Plane               │
  │  (Istio Pilot / custom xDS server)  │
  └──────────┬───────────────────────────┘
             │
    ┌────────┴──────────────────┐
    │                           │
    ▼                           ▼
  [Envoy A]                [Envoy B]

  xDS 유형:
  ├── LDS (Listener Discovery Service)
  │   → 리스너 설정 동적 변경
  ├── RDS (Route Discovery Service)
  │   → 라우팅 규칙 동적 변경
  ├── CDS (Cluster Discovery Service)
  │   → 클러스터(업스트림) 동적 변경
  ├── EDS (Endpoint Discovery Service)
  │   → 엔드포인트(IP:Port) 동적 변경
  ├── SDS (Secret Discovery Service)
  │   → TLS 인증서 동적 변경
  └── ECDS (Extension Config Discovery)
      → 필터 설정 동적 변경

# Envoy WASM Filter 설정 예시
http_filters:
  - name: envoy.filters.http.wasm
    typed_config:
      "@type": type.googleapis.com/udpa.type.v1.TypedStruct
      type_url: type.googleapis.com/envoy.extensions.filters.http.wasm.v3.Wasm
      value:
        config:
          name: "custom_rate_limiter"
          root_id: "rate_limiter"
          vm_config:
            runtime: "envoy.wasm.runtime.v8"
            code:
              local:
                filename: "/etc/envoy/wasm/rate_limiter.wasm"
            allow_precompiled: true
          configuration:
            "@type": type.googleapis.com/google.protobuf.StringValue
            value: |
              {
                "max_requests_per_second": 100,
                "burst_size": 20,
                "response_code": 429
              }

AWS API Gateway 3가지 유형:

┌──────────────┬───────────────┬───────────────┬───────────────┐
│              │  REST API      │  HTTP API      │  WebSocket    │
├──────────────┼───────────────┼───────────────┼───────────────┤
│ 프로토콜     │ REST           │ REST           │ WebSocket     │
│ 레이턴시     │ 보통           │ 낮음 (~35%)    │ 보통          │
│ 가격         │ 높음           │ 낮음 (~70%)    │ 메시지당      │
│ 캐싱         │ O              │ X              │ X             │
│ Usage Plans  │ O              │ X              │ X             │
│ API Keys     │ O              │ X              │ X             │
│ WAF 통합     │ O              │ X              │ X             │
│ Request 검증 │ O              │ Parameter만    │ X             │
│ Custom Domain│ O              │ O              │ O             │
│ Lambda 통합  │ O              │ O              │ O             │
│ VPC Link     │ O              │ O              │ X             │
│ 권장 사용    │ 풀기능 필요    │ 단순 프록시    │ 실시간 통신   │
└──────────────┴───────────────┴───────────────┴───────────────┘

# SAM Template - REST API Gateway
AWSTemplateFormatVersion: '2010-09-09'
Transform: AWS::Serverless-2016-10-31

Globals:
  Api:
    Cors:
      AllowMethods: "'GET,POST,PUT,DELETE,OPTIONS'"
      AllowHeaders: "'Content-Type,Authorization,X-Api-Key'"
      AllowOrigin: "'https://app.company.com'"

Resources:
  ApiGateway:
    Type: AWS::Serverless::Api
    Properties:
      StageName: prod
      Auth:
        DefaultAuthorizer: CognitoAuth
        Authorizers:
          CognitoAuth:
            UserPoolArn: !GetAtt UserPool.Arn
            Identity:
              Header: Authorization
        ApiKeyRequired: true
        UsagePlan:
          CreateUsagePlan: PER_API
          UsagePlanName: "StandardPlan"
          Throttle:
            BurstLimit: 100
            RateLimit: 50
          Quota:
            Limit: 10000
            Period: DAY
      MethodSettings:
        - HttpMethod: "*"
          ResourcePath: "/*"
          ThrottlingBurstLimit: 200
          ThrottlingRateLimit: 100
          CachingEnabled: true
          CacheTtlInSeconds: 300
          LoggingLevel: INFO
          MetricsEnabled: true

  # User Function
  UserFunction:
    Type: AWS::Serverless::Function
    Properties:
      Handler: handlers/user.handler
      Runtime: nodejs20.x
      MemorySize: 256
      Timeout: 10
      Events:
        GetUsers:
          Type: Api
          Properties:
            RestApiId: !Ref ApiGateway
            Path: /api/v1/users
            Method: GET
        CreateUser:
          Type: Api
          Properties:
            RestApiId: !Ref ApiGateway
            Path: /api/v1/users
            Method: POST

  # Order Function
  OrderFunction:
    Type: AWS::Serverless::Function
    Properties:
      Handler: handlers/order.handler
      Runtime: nodejs20.x
      MemorySize: 512
      Timeout: 15
      Events:
        GetOrders:
          Type: Api
          Properties:
            RestApiId: !Ref ApiGateway
            Path: /api/v1/orders
            Method: GET
        CreateOrder:
          Type: Api
          Properties:
            RestApiId: !Ref ApiGateway
            Path: /api/v1/orders
            Method: POST

  # Cognito User Pool
  UserPool:
    Type: AWS::Cognito::UserPool
    Properties:
      UserPoolName: api-user-pool
      AutoVerifiedAttributes:
        - email
      MfaConfiguration: "OPTIONAL"
      Policies:
        PasswordPolicy:
          MinimumLength: 12
          RequireUppercase: true
          RequireLowercase: true
          RequireNumbers: true
          RequireSymbols: true

// authorizer.js - Lambda Custom Authorizer
const jwt = require('jsonwebtoken');

const JWKS_CACHE = {};

exports.handler = async (event) => {
  try {
    const token = extractToken(event.authorizationToken);
    if (!token) {
      throw new Error('Unauthorized');
    }

    // JWT 검증
    const decoded = await verifyToken(token);

    // IAM Policy 생성
    const policy = generatePolicy(
      decoded.sub,
      'Allow',
      event.methodArn,
      {
        userId: decoded.sub,
        email: decoded.email,
        role: decoded.role,
        plan: decoded.plan || 'free'
      }
    );

    return policy;
  } catch (error) {
    console.error('Authorization failed:', error.message);
    throw new Error('Unauthorized');
  }
};

function extractToken(authHeader) {
  if (!authHeader) return null;
  const parts = authHeader.split(' ');
  if (parts.length !== 2 || parts[0] !== 'Bearer') return null;
  return parts[1];
}

async function verifyToken(token) {
  const decoded = jwt.decode(token, { complete: true });
  if (!decoded) throw new Error('Invalid token');

  // JWKS에서 공개키 가져오기
  const publicKey = await getPublicKey(decoded.header.kid);

  return jwt.verify(token, publicKey, {
    algorithms: ['RS256'],
    issuer: process.env.TOKEN_ISSUER,
    audience: process.env.TOKEN_AUDIENCE,
  });
}

function generatePolicy(principalId, effect, resource, context) {
  const [arn, partition, service, region, accountId, apiId, stage] =
    resource.split(/[:/]/);

  return {
    principalId,
    policyDocument: {
      Version: '2012-10-17',
      Statement: [{
        Action: 'execute-api:Invoke',
        Effect: effect,
        Resource: `arn:${partition}:${service}:${region}:${accountId}:${apiId}/${stage}/*`
      }]
    },
    context: context || {}
  };
}

Traefik Architecture:

  [클라이언트]
       │
  ┌────┴────────────────────────────────┐
  │           Traefik Proxy              │
  │                                      │
  │  EntryPoints (포트)                  │
  │    ├── :80 (web)                     │
  │    └── :443 (websecure)              │
  │         │                            │
  │  Routers (라우팅 규칙)               │
  │    ├── Host / Path / Header 매칭     │
  │    ├── TLS 설정                      │
  │    └── Middleware 체인               │
  │         │                            │
  │  Middlewares (중간 처리)             │
  │    ├── RateLimit                     │
  │    ├── BasicAuth / ForwardAuth       │
  │    ├── Headers                       │
  │    ├── Retry                         │
  │    ├── CircuitBreaker                │
  │    └── StripPrefix                   │
  │         │                            │
  │  Services (백엔드)                   │
  │    ├── LoadBalancer                  │
  │    ├── Weighted                      │
  │    └── Mirroring                     │
  │                                      │
  │  Providers (설정 소스 - 자동 발견)   │
  │    ├── Docker                        │
  │    ├── Kubernetes                    │
  │    ├── File                          │
  │    └── Consul / etcd                 │
  └──────────────────────────────────────┘

# docker-compose.yml with Traefik
version: "3.8"

services:
  traefik:
    image: traefik:v3.0
    command:
      - "--api.dashboard=true"
      - "--providers.docker=true"
      - "--providers.docker.exposedByDefault=false"
      - "--entrypoints.web.address=:80"
      - "--entrypoints.websecure.address=:443"
      - "--certificatesresolvers.letsencrypt.acme.httpchallenge=true"
      - "--certificatesresolvers.letsencrypt.acme.httpchallenge.entrypoint=web"
      - "--certificatesresolvers.letsencrypt.acme.email=admin@company.com"
      - "--certificatesresolvers.letsencrypt.acme.storage=/letsencrypt/acme.json"
      - "--metrics.prometheus=true"
      - "--accesslog=true"
      - "--accesslog.format=json"
    ports:
      - "80:80"
      - "443:443"
      - "8080:8080"
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock:ro
      - letsencrypt:/letsencrypt

  user-service:
    image: user-service:latest
    labels:
      - "traefik.enable=true"
      - "traefik.http.routers.users.rule=Host(`api.company.com`) && PathPrefix(`/api/v1/users`)"
      - "traefik.http.routers.users.entrypoints=websecure"
      - "traefik.http.routers.users.tls.certresolver=letsencrypt"
      - "traefik.http.routers.users.middlewares=rate-limit,auth-forward"
      - "traefik.http.services.users.loadbalancer.server.port=8080"
      - "traefik.http.services.users.loadbalancer.healthcheck.path=/health"
      - "traefik.http.services.users.loadbalancer.healthcheck.interval=10s"

  order-service:
    image: order-service:latest
    labels:
      - "traefik.enable=true"
      - "traefik.http.routers.orders.rule=Host(`api.company.com`) && PathPrefix(`/api/v1/orders`)"
      - "traefik.http.routers.orders.entrypoints=websecure"
      - "traefik.http.routers.orders.tls.certresolver=letsencrypt"
      - "traefik.http.routers.orders.middlewares=rate-limit,auth-forward"
      - "traefik.http.services.orders.loadbalancer.server.port=8080"

  # Middleware 정의
  # Rate Limiting
  rate-limit:
    labels:
      - "traefik.http.middlewares.rate-limit.ratelimit.average=100"
      - "traefik.http.middlewares.rate-limit.ratelimit.burst=50"
      - "traefik.http.middlewares.rate-limit.ratelimit.period=1m"

volumes:
  letsencrypt:

# Traefik IngressRoute CRD
apiVersion: traefik.io/v1alpha1
kind: IngressRoute
metadata:
  name: api-routes
  namespace: production
spec:
  entryPoints:
    - websecure
  routes:
    - match: Host(`api.company.com`) && PathPrefix(`/api/v1/users`)
      kind: Rule
      services:
        - name: user-service
          port: 8080
          weight: 100
      middlewares:
        - name: rate-limit
        - name: jwt-auth
        - name: cors-headers

    - match: Host(`api.company.com`) && PathPrefix(`/api/v1/products`)
      kind: Rule
      services:
        - name: product-service-v1
          port: 8080
          weight: 90
        - name: product-service-v2
          port: 8080
          weight: 10
  tls:
    certResolver: letsencrypt
---
apiVersion: traefik.io/v1alpha1
kind: Middleware
metadata:
  name: rate-limit
  namespace: production
spec:
  rateLimit:
    average: 100
    burst: 50
    period: 1m
    sourceCriterion:
      ipStrategy:
        depth: 1
---
apiVersion: traefik.io/v1alpha1
kind: Middleware
metadata:
  name: jwt-auth
  namespace: production
spec:
  forwardAuth:
    address: http://auth-service:8080/verify
    authResponseHeaders:
      - X-User-ID
      - X-User-Role

# JWT 검증 미들웨어 (Python/FastAPI 예시)
from fastapi import Request, HTTPException
from jose import jwt, JWTError, ExpiredSignatureError
import httpx
from functools import lru_cache

class JWTAuthMiddleware:
    def __init__(self, jwks_url: str, issuer: str, audience: str):
        self.jwks_url = jwks_url
        self.issuer = issuer
        self.audience = audience
        self._jwks_cache = None

    async def get_jwks(self):
        """JWKS (JSON Web Key Set) 가져오기 및 캐시"""
        if self._jwks_cache is None:
            async with httpx.AsyncClient() as client:
                response = await client.get(self.jwks_url)
                self._jwks_cache = response.json()
        return self._jwks_cache

    async def verify_token(self, request: Request) -> dict:
        """요청에서 JWT를 추출하고 검증"""
        # 1. Authorization 헤더에서 토큰 추출
        auth_header = request.headers.get("Authorization")
        if not auth_header or not auth_header.startswith("Bearer "):
            raise HTTPException(
                status_code=401,
                detail="Missing or invalid Authorization header"
            )

        token = auth_header.split(" ")[1]

        try:
            # 2. 토큰 헤더에서 kid 추출
            unverified_header = jwt.get_unverified_header(token)
            kid = unverified_header.get("kid")

            # 3. JWKS에서 해당 키 찾기
            jwks = await self.get_jwks()
            key = None
            for jwk in jwks.get("keys", []):
                if jwk["kid"] == kid:
                    key = jwk
                    break

            if key is None:
                # 캐시 갱신 후 재시도
                self._jwks_cache = None
                jwks = await self.get_jwks()
                for jwk in jwks.get("keys", []):
                    if jwk["kid"] == kid:
                        key = jwk
                        break

            if key is None:
                raise HTTPException(status_code=401, detail="Unknown signing key")

            # 4. JWT 검증
            payload = jwt.decode(
                token,
                key,
                algorithms=["RS256"],
                audience=self.audience,
                issuer=self.issuer,
            )

            return payload

        except ExpiredSignatureError:
            raise HTTPException(status_code=401, detail="Token expired")
        except JWTError as e:
            raise HTTPException(status_code=401, detail=f"Invalid token: {str(e)}")

OAuth2 Authorization Code Flow + PKCE:

  [브라우저/앱]                   [API Gateway]       [Auth Server]    [Backend]
       │                              │                    │               │
       │  1. 로그인 요청              │                    │               │
       │─────────────────────────────▶│                    │               │
       │                              │                    │               │
       │  2. Auth Server로 리다이렉트 │                    │               │
       │◀─────────────────────────────│                    │               │
       │                              │                    │               │
       │  3. 인증 (ID/PW 또는 SSO)    │                    │               │
       │──────────────────────────────────────────────────▶│               │
       │                              │                    │               │
       │  4. Authorization Code 반환  │                    │               │
       │◀──────────────────────────────────────────────────│               │
       │                              │                    │               │
       │  5. Code + PKCE verifier     │                    │               │
       │─────────────────────────────▶│                    │               │
       │                              │  6. Code -> Token  │               │
       │                              │───────────────────▶│               │
       │                              │  7. Access Token   │               │
       │                              │◀───────────────────│               │
       │                              │                    │               │
       │  8. Access Token             │                    │               │
       │◀─────────────────────────────│                    │               │
       │                              │                    │               │
       │  9. API 요청 + Bearer Token  │                    │               │
       │─────────────────────────────▶│                    │               │
       │                              │ 10. Token 검증     │               │
       │                              │───────────────────▶│               │
       │                              │ 11. 검증 결과      │               │
       │                              │◀───────────────────│               │
       │                              │ 12. 요청 전달      │               │
       │                              │───────────────────────────────────▶│
       │                              │ 13. 응답           │               │
       │                              │◀───────────────────────────────────│
       │  14. API 응답                │                    │               │
       │◀─────────────────────────────│                    │               │

# API Key 관리 시스템
import hashlib
import secrets
from datetime import datetime, timedelta

class APIKeyManager:
    def __init__(self, db):
        self.db = db

    def generate_key(
        self,
        consumer_id: str,
        plan: str = "free",
        expires_in_days: int = 365
    ) -> dict:
        """새 API Key 생성"""
        # prefix + secret 형식 (sk_live_xxxx)
        prefix = f"sk_{'live' if plan != 'free' else 'test'}"
        raw_key = f"{prefix}_{secrets.token_urlsafe(32)}"

        # DB에는 해시만 저장
        key_hash = hashlib.sha256(raw_key.encode()).hexdigest()

        record = {
            "key_hash": key_hash,
            "key_prefix": raw_key[:12],  # 식별용 prefix만 저장
            "consumer_id": consumer_id,
            "plan": plan,
            "rate_limit": self._get_rate_limit(plan),
            "created_at": datetime.utcnow().isoformat(),
            "expires_at": (
                datetime.utcnow() + timedelta(days=expires_in_days)
            ).isoformat(),
            "is_active": True,
        }

        self.db.insert("api_keys", record)

        return {
            "api_key": raw_key,  # 한 번만 반환, 이후 조회 불가
            "prefix": raw_key[:12],
            "plan": plan,
            "expires_at": record["expires_at"],
        }

    def validate_key(self, raw_key: str) -> dict:
        """API Key 검증"""
        key_hash = hashlib.sha256(raw_key.encode()).hexdigest()

        record = self.db.find_one("api_keys", {"key_hash": key_hash})

        if not record:
            return {"valid": False, "error": "Invalid API key"}

        if not record["is_active"]:
            return {"valid": False, "error": "API key is deactivated"}

        if datetime.fromisoformat(record["expires_at"]) < datetime.utcnow():
            return {"valid": False, "error": "API key expired"}

        return {
            "valid": True,
            "consumer_id": record["consumer_id"],
            "plan": record["plan"],
            "rate_limit": record["rate_limit"],
        }

    def _get_rate_limit(self, plan: str) -> dict:
        limits = {
            "free":       {"rpm": 60,    "rpd": 1000},
            "starter":    {"rpm": 300,   "rpd": 10000},
            "pro":        {"rpm": 1000,  "rpd": 100000},
            "enterprise": {"rpm": 10000, "rpd": 1000000},
        }
        return limits.get(plan, limits["free"])

import time
import threading

class TokenBucket:
    """Token Bucket 레이트 리미터

    특징:
    - 일정 속도로 토큰이 버킷에 추가됨
    - 요청 시 토큰 1개 소비
    - 토큰 없으면 요청 거부
    - 버스트 허용 (버킷이 가득 찰 때까지)
    """

    def __init__(self, rate: float, capacity: int):
        self.rate = rate          # 초당 토큰 생성 속도
        self.capacity = capacity  # 버킷 최대 크기 (버스트 허용량)
        self.tokens = capacity    # 현재 토큰 수
        self.last_refill = time.monotonic()
        self.lock = threading.Lock()

    def allow_request(self) -> bool:
        with self.lock:
            now = time.monotonic()
            elapsed = now - self.last_refill

            # 토큰 보충
            self.tokens = min(
                self.capacity,
                self.tokens + elapsed * self.rate
            )
            self.last_refill = now

            if self.tokens >= 1:
                self.tokens -= 1
                return True
            return False

    def get_retry_after(self) -> float:
        """다음 토큰까지 남은 시간 (초)"""
        if self.tokens >= 1:
            return 0
        return (1 - self.tokens) / self.rate


# 사용 예시
limiter = TokenBucket(rate=10, capacity=20)
# rate=10: 초당 10개 토큰 생성
# capacity=20: 최대 20개 토큰 저장 (버스트 20)

for i in range(25):
    if limiter.allow_request():
        print(f"Request {i}: ALLOWED")
    else:
        retry = limiter.get_retry_after()
        print(f"Request {i}: DENIED (retry after {retry:.2f}s)")

import time
from collections import deque
import threading

class SlidingWindowLog:
    """Sliding Window Log 레이트 리미터

    특징:
    - 정확한 윈도우 기반 제한
    - 메모리 사용량이 요청 수에 비례
    - 경계 문제 없음 (Fixed Window 대비 장점)
    """

    def __init__(self, max_requests: int, window_seconds: int):
        self.max_requests = max_requests
        self.window_seconds = window_seconds
        self.requests = deque()  # 타임스탬프 로그
        self.lock = threading.Lock()

    def allow_request(self) -> bool:
        with self.lock:
            now = time.monotonic()
            window_start = now - self.window_seconds

            # 윈도우 밖의 오래된 요청 제거
            while self.requests and self.requests[0] < window_start:
                self.requests.popleft()

            if len(self.requests) < self.max_requests:
                self.requests.append(now)
                return True
            return False

    def get_remaining(self) -> int:
        with self.lock:
            now = time.monotonic()
            window_start = now - self.window_seconds
            while self.requests and self.requests[0] < window_start:
                self.requests.popleft()
            return max(0, self.max_requests - len(self.requests))


# 사용 예시
limiter = SlidingWindowLog(max_requests=100, window_seconds=60)
# 60초 동안 최대 100개 요청

import time
import threading
from collections import defaultdict

class FixedWindowCounter:
    """Fixed Window Counter 레이트 리미터

    특징:
    - 메모리 효율적 (카운터만 저장)
    - 윈도우 경계에서 2배 버스트 가능 (단점)
    - 구현이 단순함
    """

    def __init__(self, max_requests: int, window_seconds: int):
        self.max_requests = max_requests
        self.window_seconds = window_seconds
        self.counters = defaultdict(int)
        self.lock = threading.Lock()

    def _get_window_key(self) -> int:
        return int(time.time() // self.window_seconds)

    def allow_request(self, client_id: str = "global") -> bool:
        with self.lock:
            window = self._get_window_key()
            key = f"{client_id}:{window}"

            # 이전 윈도우 정리
            old_keys = [
                k for k in self.counters
                if not k.endswith(f":{window}")
            ]
            for k in old_keys:
                del self.counters[k]

            if self.counters[key] < self.max_requests:
                self.counters[key] += 1
                return True
            return False

import redis
import time

class DistributedRateLimiter:
    """Redis 기반 분산 레이트 리미터 (Sliding Window Counter)"""

    def __init__(self, redis_client: redis.Redis, prefix: str = "rl"):
        self.redis = redis_client
        self.prefix = prefix

    def is_allowed(
        self,
        key: str,
        max_requests: int,
        window_seconds: int
    ) -> dict:
        """
        Sliding Window Counter (Redis Sorted Set 사용)
        """
        now = time.time()
        window_start = now - window_seconds
        redis_key = f"{self.prefix}:{key}"

        pipe = self.redis.pipeline()

        # 1. 윈도우 밖의 오래된 항목 제거
        pipe.zremrangebyscore(redis_key, 0, window_start)

        # 2. 현재 윈도우의 요청 수 조회
        pipe.zcard(redis_key)

        # 3. 현재 요청 추가
        pipe.zadd(redis_key, {f"{now}:{id(object())}": now})

        # 4. TTL 설정 (윈도우 크기 + 여유)
        pipe.expire(redis_key, window_seconds + 1)

        results = pipe.execute()
        current_count = results[1]

        if current_count < max_requests:
            remaining = max_requests - current_count - 1
            return {
                "allowed": True,
                "remaining": max(0, remaining),
                "reset_at": int(now + window_seconds),
                "limit": max_requests,
            }
        else:
            # 방금 추가한 요청 제거
            self.redis.zrem(redis_key, f"{now}:{id(object())}")
            return {
                "allowed": False,
                "remaining": 0,
                "reset_at": int(now + window_seconds),
                "limit": max_requests,
                "retry_after": window_seconds,
            }

# Kong Request Transformer 예시
plugins:
  - name: request-transformer
    config:
      add:
        headers:
          - "X-Gateway-Version:2.0"
          - "X-Request-Start:$(now)"
        querystring:
          - "format:json"
      rename:
        headers:
          - "X-Old-Header:X-New-Header"
      remove:
        headers:
          - "X-Internal-Debug"
      replace:
        headers:
          - "Host:internal-api.company.com"

  - name: response-transformer
    config:
      add:
        headers:
          - "X-Response-Time:$(latency)"
          - "X-RateLimit-Remaining:$(rate_limit_remaining)"
      remove:
        headers:
          - "Server"
          - "X-Powered-By"
          - "X-Backend-Server"
      replace:
        headers:
          - "Content-Security-Policy:default-src 'self'"

API Gateway 캐싱 전략:

1. Response Cache (응답 캐싱)
   ┌──────────┐     ┌──────────┐     ┌──────────┐
   │ 클라이언트│────▶│  Gateway │────▶│  Backend │
   │          │     │  Cache   │     │          │
   │          │◀────│  (Hit!)  │     │          │
   └──────────┘     └──────────┘     └──────────┘

   Cache Key = Method + Path + Query + Selected Headers
   TTL: GET /products → 5분, GET /products/123 → 1분

2. 캐시 무효화 전략:
   - TTL 기반: 시간이 지나면 자동 만료
   - Event 기반: 데이터 변경 시 캐시 퍼지
   - Stale-While-Revalidate: 만료 후에도 캐시 반환, 백그라운드 갱신

3. Cache-Control 헤더:
   Cache-Control: public, max-age=300, s-maxage=600
   ETag: "v1-product-123-hash"
   Vary: Accept, Authorization

# Kong Proxy Cache 설정
plugins:
  - name: proxy-cache
    config:
      strategy: memory
      memory:
        dictionary_name: cache_dict
      response_code:
        - 200
        - 301
      request_method:
        - GET
        - HEAD
      content_type:
        - "application/json"
        - "text/html"
      cache_ttl: 300
      vary_headers:
        - Accept
        - Accept-Encoding
      vary_query_params:
        - page
        - limit
        - sort
      cache_control: true
      storage_ttl: 600

Circuit Breaker 상태:

  ┌──────────┐    실패율 초과     ┌──────────┐
  │  CLOSED  │──────────────────▶│   OPEN   │
  │ (정상)   │                   │ (차단)   │
  └──────────┘                   └────┬─────┘
       ▲                              │
       │                    타임아웃 후 │
       │      성공          ┌─────────┴──┐
       └────────────────────│ HALF-OPEN  │
                            │ (테스트)   │
                            └────────────┘
                              │
                         실패 시 → 다시 OPEN

# Envoy Circuit Breaker 설정
clusters:
  - name: order_service
    circuit_breakers:
      thresholds:
        - priority: DEFAULT
          max_connections: 1024         # 최대 동시 연결
          max_pending_requests: 512     # 대기 중 최대 요청
          max_requests: 2048            # 최대 동시 요청
          max_retries: 3                # 최대 재시도
          track_remaining: true
    outlier_detection:
      consecutive_5xx: 5              # 연속 5xx 5회 시 제거
      interval: 10s                   # 분석 주기
      base_ejection_time: 30s         # 기본 제거 시간
      max_ejection_percent: 50        # 최대 제거 비율
      success_rate_minimum_hosts: 3   # 통계에 필요한 최소 호스트
      success_rate_request_volume: 100 # 통계에 필요한 최소 요청
      success_rate_stdev_factor: 1900  # 표준편차 기반 제거

# Envoy Weighted Routing (카나리 배포)
route_config:
  virtual_hosts:
    - name: api
      domains: ["api.company.com"]
      routes:
        - match:
            prefix: "/api/v1/products"
          route:
            weighted_clusters:
              clusters:
                - name: product_v1
                  weight: 90
                - name: product_v2
                  weight: 10
            retry_policy:
              retry_on: "5xx"
              num_retries: 2

        # Header 기반 A/B 라우팅
        - match:
            prefix: "/api/v1/checkout"
            headers:
              - name: "X-Feature-Flag"
                exact_match: "new-checkout"
          route:
            cluster: checkout_v2
        - match:
            prefix: "/api/v1/checkout"
          route:
            cluster: checkout_v1

# Kong Canary Release 플러그인
plugins:
  - name: canary
    config:
      start: 0           # 시작 비율 (%)
      target: 100         # 목표 비율 (%)
      steps: 10           # 단계 수
      duration: 3600      # 전환 시간 (초)
      upstream_host: "product-v2:8080"
      upstream_port: 8080
      hash: "consumer"    # consumer/ip/header 기반 일관된 라우팅

GraphQL Federation Architecture:

  [클라이언트]
       │
  ┌────┴────────────────────────┐
  │     Apollo Router           │
  │     (Supergraph Gateway)    │
  │                             │
  │  ┌───────────────────────┐  │
  │  │  Query Planner        │  │
  │  │  → 어떤 서브그래프에   │  │
  │  │    어떤 쿼리를 보낼지  │  │
  │  │    최적 계획 수립      │  │
  │  └───────────────────────┘  │
  └──────┬──────┬──────┬────────┘
         │      │      │
    ┌────┴──┐ ┌┴────┐ ┌┴────────┐
    │ User  │ │Order│ │ Product  │
    │Subgraph│ │Sub- │ │Subgraph  │
    │       │ │graph│ │          │
    └───────┘ └─────┘ └──────────┘

# User Subgraph Schema
type User @key(fields: "id") {
  id: ID!
  name: String!
  email: String!
  orders: [Order]
}

type Query {
  user(id: ID!): User
  users(limit: Int, offset: Int): [User]
}

# Apollo Router 설정
# router.yaml
supergraph:
  listen: 0.0.0.0:4000

headers:
  all:
    request:
      - propagate:
          named: "Authorization"
      - propagate:
          named: "X-Request-ID"

traffic_shaping:
  all:
    timeout: 30s
  subgraphs:
    users:
      timeout: 10s
    orders:
      timeout: 15s

limits:
  max_depth: 15
  max_height: 200
  max_aliases: 30
  max_root_fields: 20

telemetry:
  exporters:
    metrics:
      prometheus:
        enabled: true
        listen: 0.0.0.0:9090
        path: /metrics
    tracing:
      otlp:
        enabled: true
        endpoint: http://otel-collector:4317

cors:
  origins:
    - https://app.company.com
  methods:
    - GET
    - POST
  allow_headers:
    - Authorization
    - Content-Type

ratelimit:
  global:
    capacity: 1000
    interval: 1m

3가지 API 버저닝 전략:

1. URL Path Versioning
   GET /api/v1/users
   GET /api/v2/users
   → 가장 직관적, 널리 사용
   → 캐싱 친화적
   → URL이 바뀜 (Breaking)

2. Header Versioning
   GET /api/users
   Accept: application/vnd.company.v2+json
   → URL 깔끔
   → 브라우저에서 테스트 어려움

3. Query Parameter Versioning
   GET /api/users?version=2
   → 간단
   → 캐싱 복잡
   → 쿼리 파라미터 오염

# Kong Route 기반 버저닝
services:
  - name: user-service-v1
    url: http://user-service-v1:8080
    routes:
      - name: users-v1
        paths:
          - /api/v1/users
        strip_path: false

  - name: user-service-v2
    url: http://user-service-v2:8080
    routes:
      - name: users-v2
        paths:
          - /api/v2/users
        strip_path: false

  # Header 기반 버저닝
  - name: user-service-v2-header
    url: http://user-service-v2:8080
    routes:
      - name: users-v2-header
        paths:
          - /api/users
        headers:
          X-API-Version:
            - "2"
        strip_path: false

  # 디폴트 (최신 안정 버전)
  - name: user-service-stable
    url: http://user-service-v1:8080
    routes:
      - name: users-default
        paths:
          - /api/users
        strip_path: false

# API Gateway 핵심 메트릭

# 1. 4 Golden Signals
golden_signals:
  latency:
    - histogram: api_request_duration_seconds
      labels: [method, route, status_code]
      buckets: [0.01, 0.05, 0.1, 0.25, 0.5, 1, 2.5, 5, 10]

  traffic:
    - counter: api_requests_total
      labels: [method, route, status_code, consumer]

  errors:
    - counter: api_errors_total
      labels: [method, route, error_type]

  saturation:
    - gauge: api_active_connections
    - gauge: api_rate_limit_remaining
    - gauge: api_circuit_breaker_state

# 2. 레이트 리밋 메트릭
rate_limiting:
  - counter: api_rate_limit_hits_total
    labels: [consumer, plan, route]
  - gauge: api_rate_limit_remaining
    labels: [consumer, route]

# 3. 캐시 메트릭
caching:
  - counter: api_cache_hits_total
  - counter: api_cache_misses_total
  - gauge: api_cache_size_bytes

# 4. 업스트림 메트릭
upstream:
  - histogram: api_upstream_latency_seconds
    labels: [service, status]
  - counter: api_upstream_errors_total
    labels: [service, error_type]
  - gauge: api_upstream_healthy_count
    labels: [service]

# Grafana 대시보드 쿼리 예시
panels:
  - title: "Request Rate (RPS)"
    query: |
      sum(rate(api_requests_total[5m])) by (route)

  - title: "P99 Latency"
    query: |
      histogram_quantile(0.99,
        sum(rate(api_request_duration_seconds_bucket[5m])) by (le, route)
      )

  - title: "Error Rate"
    query: |
      sum(rate(api_requests_total{status_code=~"5.."}[5m]))
      /
      sum(rate(api_requests_total[5m]))
      * 100

  - title: "Rate Limit Hits"
    query: |
      sum(rate(api_rate_limit_hits_total[5m])) by (consumer)

  - title: "Circuit Breaker Status"
    query: |
      api_circuit_breaker_state

API Gateway 분산 트레이싱 흐름:

  Request ID: abc-123-def

  [Client] ─────────── [API Gateway] ──────── [User Service] ──── [DB]
      │                     │                       │               │
      │ Span: client-req   │ Span: gateway         │ Span: user-svc│ Span: db-query
      │ trace_id: abc123   │ trace_id: abc123      │ trace_id: abc123
      │ span_id: span-1    │ span_id: span-2       │ span_id: span-3
      │ parent: none       │ parent: span-1        │ parent: span-2
      │ duration: 250ms    │ duration: 200ms       │ duration: 150ms
      │                    │                        │
      │ Tags:              │ Tags:                  │ Tags:
      │  http.method: GET  │  gateway.auth: jwt     │  db.type: postgres
      │  http.url: /users  │  gateway.cache: miss   │  db.statement: SELECT
      │  http.status: 200  │  consumer: user-123    │  db.duration: 50ms