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ServiceEntry ​

ServiceEntry는 Istio 서비스 메시에 외부 서비스를 등록하여 메시 내부 서비스처럼 관리할 수 있게 합니다.

목차 ​

  1. Why ServiceEntry?
  2. ServiceEntry 개요
  3. Resolution 모드
  4. Location 설정
  5. 실전 예제
  6. Egress Gateway와 조합
  7. 보안 및 TLS
  8. 모니터링 및 제어
  9. 모범 사례

Why ServiceEntry? ​

외부 서비스 관리의 필요성 ​

Istio 메시는 기본적으로 외부 서비스에 대한 트래픽을 제어하지 않습니다. ServiceEntry를 사용하면:

주요 이점 ​

기능ServiceEntry 없이ServiceEntry 사용
모니터링블랙홀전체 메트릭 수집
트래픽 제어불가능Timeout, Retry, Circuit Breaker
보안제한적mTLS, 인증서 관리
Egress Control모든 외부 트래픽 허용명시적 허용/차단
서비스 디스커버리수동 관리자동 DNS 조회

ServiceEntry 개요 ​

ServiceEntry는 외부 서비스를 Istio 서비스 레지스트리에 추가합니다.

기본 구조 ​

yaml
apiVersion: networking.istio.io/v1
kind: ServiceEntry
metadata:
  name: external-api
spec:
  hosts:                  # 외부 서비스 호스트명
  - api.example.com
  ports:                  # 포트 및 프로토콜
  - number: 443
    name: https
    protocol: HTTPS
  location: MESH_EXTERNAL # 외부/내부 위치
  resolution: DNS         # 주소 해석 방법

Resolution 모드 ​

ServiceEntry는 4가지 주소 해석 모드를 지원합니다.

1. DNS Resolution ​

가장 일반적인 모드로, DNS를 통해 IP 주소를 동적으로 해석합니다.

yaml
apiVersion: networking.istio.io/v1
kind: ServiceEntry
metadata:
  name: external-api-dns
spec:
  hosts:
  - api.example.com
  ports:
  - number: 443
    name: https
    protocol: HTTPS
  location: MESH_EXTERNAL
  resolution: DNS  # DNS 조회

사용 사례:

  • 공개 API (AWS S3, Google Cloud Storage)
  • SaaS 서비스 (Stripe, SendGrid)
  • 클라우드 관리 서비스

2. STATIC Resolution ​

고정 IP 주소를 명시적으로 지정합니다.

yaml
apiVersion: networking.istio.io/v1
kind: ServiceEntry
metadata:
  name: external-api-static
spec:
  hosts:
  - legacy-api.company.internal
  addresses:
  - 10.10.10.10
  - 10.10.10.11
  ports:
  - number: 8080
    name: http
    protocol: HTTP
  location: MESH_EXTERNAL
  resolution: STATIC  # 고정 IP
  endpoints:
  - address: 10.10.10.10
  - address: 10.10.10.11

사용 사례:

  • 레거시 시스템 (DNS 없음)
  • 고정 IP가 필요한 규정 준수
  • 내부 데이터센터 서비스

3. NONE Resolution ​

주소 해석을 수행하지 않고, 클라이언트가 제공한 주소를 그대로 사용합니다.

yaml
apiVersion: networking.istio.io/v1
kind: ServiceEntry
metadata:
  name: wildcard-api
spec:
  hosts:
  - "*.api.example.com"  # 와일드카드
  ports:
  - number: 443
    name: https
    protocol: HTTPS
  location: MESH_EXTERNAL
  resolution: NONE  # 주소 해석 없음

사용 사례:

  • 와일드카드 도메인
  • 클라이언트 측 로드 밸런싱
  • TCP/TLS 프록시

4. DNS_ROUND_ROBIN Resolution (Deprecated) ​

DNS 라운드 로빈을 사용합니다 (현재는 DNS 모드로 통합).

Location 설정 ​

MESH_EXTERNAL (외부 서비스) ​

메시 외부의 서비스를 등록합니다.

yaml
apiVersion: networking.istio.io/v1
kind: ServiceEntry
metadata:
  name: external-service
spec:
  hosts:
  - external-api.com
  ports:
  - number: 443
    name: https
    protocol: HTTPS
  location: MESH_EXTERNAL  # 외부 서비스
  resolution: DNS

특징:

  • mTLS가 적용되지 않음
  • Egress Gateway를 통해 나갈 수 있음
  • 외부 트래픽으로 분류

MESH_INTERNAL (내부 서비스) ​

메시 내부 서비스로 취급합니다 (드물게 사용).

yaml
apiVersion: networking.istio.io/v1
kind: ServiceEntry
metadata:
  name: internal-vm-service
spec:
  hosts:
  - vm-service.internal
  ports:
  - number: 8080
    name: http
    protocol: HTTP
  location: MESH_INTERNAL  # 내부 서비스처럼 취급
  resolution: STATIC
  endpoints:
  - address: 10.0.0.5
    labels:
      app: vm-service

사용 사례:

  • VM 워크로드를 메시에 포함
  • Multi-cluster 환경
  • Hybrid cloud 구성

실전 예제 ​

1. 외부 REST API 등록 ​

시나리오: 결제 게이트웨이 API ​

yaml
apiVersion: networking.istio.io/v1
kind: ServiceEntry
metadata:
  name: payment-gateway-api
  namespace: production
spec:
  hosts:
  - api.payment-gateway.com
  ports:
  - number: 443
    name: https
    protocol: HTTPS
  location: MESH_EXTERNAL
  resolution: DNS
---
# VirtualService: Timeout 및 Retry 설정
apiVersion: networking.istio.io/v1
kind: VirtualService
metadata:
  name: payment-gateway-routing
  namespace: production
spec:
  hosts:
  - api.payment-gateway.com
  http:
  - route:
    - destination:
        host: api.payment-gateway.com
    timeout: 10s
    retries:
      attempts: 3
      perTryTimeout: 3s
      retryOn: 5xx,reset,connect-failure
---
# DestinationRule: Circuit Breaker
apiVersion: networking.istio.io/v1
kind: DestinationRule
metadata:
  name: payment-gateway-circuit-breaker
  namespace: production
spec:
  host: api.payment-gateway.com
  trafficPolicy:
    connectionPool:
      http:
        http1MaxPendingRequests: 10
        maxRequestsPerConnection: 1
    outlierDetection:
      consecutiveErrors: 3
      interval: 30s
      baseEjectionTime: 120s
    tls:
      mode: SIMPLE  # TLS 연결

2. 외부 데이터베이스 등록 ​

시나리오: AWS RDS MySQL ​

yaml
apiVersion: networking.istio.io/v1
kind: ServiceEntry
metadata:
  name: aws-rds-mysql
spec:
  hosts:
  - mydb.abc123.us-west-2.rds.amazonaws.com
  ports:
  - number: 3306
    name: tcp
    protocol: TCP
  location: MESH_EXTERNAL
  resolution: DNS
---
apiVersion: networking.istio.io/v1
kind: DestinationRule
metadata:
  name: aws-rds-mysql-circuit-breaker
spec:
  host: mydb.abc123.us-west-2.rds.amazonaws.com
  trafficPolicy:
    connectionPool:
      tcp:
        maxConnections: 100
        connectTimeout: 5s
    outlierDetection:
      consecutiveErrors: 5
      interval: 60s
      baseEjectionTime: 60s

3. 와일드카드 도메인 등록 ​

시나리오: AWS S3 버킷 접근 ​

yaml
apiVersion: networking.istio.io/v1
kind: ServiceEntry
metadata:
  name: aws-s3-buckets
spec:
  hosts:
  - "*.s3.amazonaws.com"
  - "*.s3.*.amazonaws.com"
  - "*.s3-*.amazonaws.com"
  ports:
  - number: 443
    name: https
    protocol: HTTPS
  location: MESH_EXTERNAL
  resolution: NONE  # 와일드카드는 NONE 사용

4. 여러 엔드포인트가 있는 외부 서비스 ​

시나리오: 멀티 리전 API ​

yaml
apiVersion: networking.istio.io/v1
kind: ServiceEntry
metadata:
  name: multi-region-api
spec:
  hosts:
  - api.global-service.com
  ports:
  - number: 443
    name: https
    protocol: HTTPS
  location: MESH_EXTERNAL
  resolution: DNS
---
apiVersion: networking.istio.io/v1
kind: VirtualService
metadata:
  name: multi-region-routing
spec:
  hosts:
  - api.global-service.com
  http:
  # 지역별 라우팅
  - match:
    - headers:
        x-region:
          exact: "us-west"
    route:
    - destination:
        host: api.global-service.com
      headers:
        request:
          set:
            Host: us-west.api.global-service.com

  - match:
    - headers:
        x-region:
          exact: "eu-central"
    route:
    - destination:
        host: api.global-service.com
      headers:
        request:
          set:
            Host: eu-central.api.global-service.com

  # 기본 라우팅
  - route:
    - destination:
        host: api.global-service.com

5. TCP 서비스 등록 ​

시나리오: 외부 Redis 클러스터 ​

yaml
apiVersion: networking.istio.io/v1
kind: ServiceEntry
metadata:
  name: external-redis
spec:
  hosts:
  - redis.external-cluster.com
  addresses:
  - 203.0.113.10
  - 203.0.113.11
  ports:
  - number: 6379
    name: tcp
    protocol: TCP
  location: MESH_EXTERNAL
  resolution: STATIC
  endpoints:
  - address: 203.0.113.10
    labels:
      instance: primary
  - address: 203.0.113.11
    labels:
      instance: replica
---
apiVersion: networking.istio.io/v1
kind: DestinationRule
metadata:
  name: external-redis-lb
spec:
  host: redis.external-cluster.com
  trafficPolicy:
    loadBalancer:
      simple: ROUND_ROBIN
    connectionPool:
      tcp:
        maxConnections: 50
        connectTimeout: 3s

Egress Gateway와 조합 ​

Egress Gateway를 통해 외부 트래픽을 중앙에서 제어합니다.

기본 Egress Gateway 설정 ​

yaml
# ServiceEntry: 외부 서비스 등록
apiVersion: networking.istio.io/v1
kind: ServiceEntry
metadata:
  name: external-api
spec:
  hosts:
  - api.example.com
  ports:
  - number: 443
    name: https
    protocol: HTTPS
  location: MESH_EXTERNAL
  resolution: DNS
---
# Gateway: Egress Gateway 설정
apiVersion: networking.istio.io/v1
kind: Gateway
metadata:
  name: egress-gateway
spec:
  selector:
    istio: egressgateway
  servers:
  - port:
      number: 443
      name: https
      protocol: HTTPS
    hosts:
    - api.example.com
    tls:
      mode: PASSTHROUGH
---
# VirtualService: 메시 내부 → Egress Gateway
apiVersion: networking.istio.io/v1
kind: VirtualService
metadata:
  name: direct-api-through-egress
spec:
  hosts:
  - api.example.com
  gateways:
  - mesh
  - egress-gateway
  http:
  - match:
    - gateways:
      - mesh
      port: 443
    route:
    - destination:
        host: istio-egressgateway.istio-system.svc.cluster.local
        port:
          number: 443
  - match:
    - gateways:
      - egress-gateway
      port: 443
    route:
    - destination:
        host: api.example.com
        port:
          number: 443

TLS Origination (메시 내부는 HTTP, 외부는 HTTPS) ​

yaml
apiVersion: networking.istio.io/v1
kind: ServiceEntry
metadata:
  name: external-http-to-https
spec:
  hosts:
  - api.secure-service.com
  ports:
  - number: 80
    name: http
    protocol: HTTP
  - number: 443
    name: https
    protocol: HTTPS
  location: MESH_EXTERNAL
  resolution: DNS
---
apiVersion: networking.istio.io/v1
kind: DestinationRule
metadata:
  name: originate-tls
spec:
  host: api.secure-service.com
  trafficPolicy:
    portLevelSettings:
    - port:
        number: 80
      tls:
        mode: SIMPLE  # HTTP → HTTPS 변환

보안 및 TLS ​

mTLS to External Service ​

yaml
apiVersion: networking.istio.io/v1
kind: ServiceEntry
metadata:
  name: mtls-external-service
spec:
  hosts:
  - mtls-api.example.com
  ports:
  - number: 443
    name: https
    protocol: HTTPS
  location: MESH_EXTERNAL
  resolution: DNS
---
apiVersion: networking.istio.io/v1
kind: DestinationRule
metadata:
  name: mtls-external-tls
spec:
  host: mtls-api.example.com
  trafficPolicy:
    tls:
      mode: MUTUAL
      clientCertificate: /etc/certs/client-cert.pem
      privateKey: /etc/certs/client-key.pem
      caCertificates: /etc/certs/ca-cert.pem

SNI Routing ​

yaml
apiVersion: networking.istio.io/v1
kind: Gateway
metadata:
  name: egress-sni-gateway
spec:
  selector:
    istio: egressgateway
  servers:
  - port:
      number: 443
      name: tls
      protocol: TLS
    hosts:
    - api.example.com
    - api2.example.com
    tls:
      mode: PASSTHROUGH
---
apiVersion: networking.istio.io/v1
kind: VirtualService
metadata:
  name: sni-routing
spec:
  hosts:
  - api.example.com
  - api2.example.com
  gateways:
  - mesh
  - egress-sni-gateway
  tls:
  - match:
    - gateways:
      - mesh
      port: 443
      sniHosts:
      - api.example.com
    route:
    - destination:
        host: istio-egressgateway.istio-system.svc.cluster.local
        port:
          number: 443
  - match:
    - gateways:
      - egress-sni-gateway
      port: 443
      sniHosts:
      - api.example.com
    route:
    - destination:
        host: api.example.com
        port:
          number: 443

모니터링 및 제어 ​

메트릭 수집 ​

bash
# ServiceEntry 트래픽 확인
kubectl exec -it <pod-name> -c istio-proxy -- \
  curl localhost:15000/stats/prometheus | grep "api.example.com"

# Egress 트래픽 메트릭
istio_requests_total{destination_service_name="api.example.com"}

Prometheus 쿼리 ​

yaml
# 외부 서비스 요청 수
sum(rate(istio_requests_total{destination_service_namespace="",destination_service_name="api.example.com"}[5m]))

# 외부 서비스 에러율
sum(rate(istio_requests_total{destination_service_name="api.example.com",response_code=~"5.."}[5m])) /
sum(rate(istio_requests_total{destination_service_name="api.example.com"}[5m]))

# 외부 서비스 응답 시간
histogram_quantile(0.95,
  sum(rate(istio_request_duration_milliseconds_bucket{destination_service_name="api.example.com"}[5m])) by (le)
)

Egress 트래픽 차단 ​

yaml
# 기본적으로 모든 Egress 차단
apiVersion: networking.istio.io/v1
kind: Sidecar
metadata:
  name: default
  namespace: default
spec:
  egress:
  - hosts:
    - "./*"  # 같은 네임스페이스만 허용
    - "istio-system/*"  # istio-system 허용
  outboundTrafficPolicy:
    mode: REGISTRY_ONLY  # ServiceEntry에 등록된 것만 허용

모범 사례 ​

1. 명시적 ServiceEntry 등록 ​

yaml
# ✅ 좋은 예: 명시적 등록
apiVersion: networking.istio.io/v1
kind: ServiceEntry
metadata:
  name: payment-api
  namespace: production
  annotations:
    description: "Payment gateway API"
    owner: "payments-team"
    sla: "99.9%"
spec:
  hosts:
  - api.payment.com
  ports:
  - number: 443
    name: https
    protocol: HTTPS
  location: MESH_EXTERNAL
  resolution: DNS

2. Circuit Breaker 필수 적용 ​

yaml
# 외부 서비스는 항상 Circuit Breaker 적용
apiVersion: networking.istio.io/v1
kind: DestinationRule
metadata:
  name: external-api-protection
spec:
  host: api.example.com
  trafficPolicy:
    connectionPool:
      http:
        http1MaxPendingRequests: 10
        maxRequestsPerConnection: 1
    outlierDetection:
      consecutiveErrors: 3
      interval: 30s
      baseEjectionTime: 120s

3. Timeout 설정 ​

yaml
# 외부 서비스는 명시적 Timeout 설정
apiVersion: networking.istio.io/v1
kind: VirtualService
metadata:
  name: external-api-timeout
spec:
  hosts:
  - api.example.com
  http:
  - route:
    - destination:
        host: api.example.com
    timeout: 10s  # 명시적 Timeout
    retries:
      attempts: 2
      perTryTimeout: 5s

4. Egress Gateway 사용 (프로덕션) ​

yaml
# 프로덕션에서는 Egress Gateway를 통해 외부 트래픽 제어
# - 중앙 집중식 모니터링
# - IP 화이트리스트 관리 용이
# - 보안 정책 일관성

5. 네임스페이스별 격리 ​

yaml
# 네임스페이스별로 ServiceEntry 격리
apiVersion: networking.istio.io/v1
kind: Sidecar
metadata:
  name: default
  namespace: team-a
spec:
  egress:
  - hosts:
    - "team-a/*"  # 자신의 네임스페이스만
    - "istio-system/*"
    - "external/*"  # 공유 외부 서비스
  outboundTrafficPolicy:
    mode: REGISTRY_ONLY

6. 문서화 템플릿 ​

yaml
apiVersion: networking.istio.io/v1
kind: ServiceEntry
metadata:
  name: external-service
  annotations:
    # 서비스 정보
    service-description: "Third-party payment API"
    service-owner: "payments-team@company.com"
    service-documentation: "https://wiki.company.com/payment-api"

    # SLA 정보
    sla-availability: "99.9%"
    sla-latency-p95: "500ms"
    rate-limit: "1000 req/min"

    # 비용 정보
    cost-per-request: "$0.01"
    monthly-budget: "$10000"

    # 장애 대응
    oncall: "payments-oncall"
    escalation: "CTO"
    fallback-strategy: "Use cached data"

참고 자료 ​