Split View: 서비스 메시(Service Mesh) 실전 가이드: Istio·Envoy·Linkerd 기반 mTLS·트래픽 관리·가시성 확보

# Benchmark results (at 2000 RPS)
# P99 latency added:
#   No mesh:          baseline
#   Linkerd:          +2.0ms
#   Istio Sidecar:    +5.8ms
#   Istio Ambient:    +2.4ms

# Resource usage (per sidecar):
#   Envoy:            ~50MB RAM, ~0.5 vCPU
#   linkerd2-proxy:   ~20MB RAM, ~0.2 vCPU

# At high load (12800 RPS) benchmarks,
# Istio Ambient recorded the lowest latency
# ~11ms difference at P99 compared to Linkerd

# Install istioctl
curl -L https://istio.io/downloadIstio | sh -
cd istio-1.24.0
export PATH=$PWD/bin:$PATH

# Install with production profile
istioctl install --set profile=default -y

# Enable automatic sidecar injection for namespace
kubectl label namespace default istio-injection=enabled

# Verify installation
istioctl verify-install
kubectl get pods -n istio-system

# VirtualService: define traffic routing rules
apiVersion: networking.istio.io/v1
kind: VirtualService
metadata:
  name: reviews-route
  namespace: default
spec:
  hosts:
    - reviews
  http:
    - match:
        - headers:
            end-user:
              exact: beta-tester
      route:
        - destination:
            host: reviews
            subset: v2
          weight: 100
    - route:
        - destination:
            host: reviews
            subset: v1
          weight: 90
        - destination:
            host: reviews
            subset: v2
          weight: 10
---
# DestinationRule: define service subsets and policies
apiVersion: networking.istio.io/v1
kind: DestinationRule
metadata:
  name: reviews-destination
  namespace: default
spec:
  host: reviews
  trafficPolicy:
    connectionPool:
      tcp:
        maxConnections: 100
      http:
        h2UpgradePolicy: DEFAULT
        http1MaxPendingRequests: 100
        http2MaxRequests: 1000
    loadBalancer:
      simple: ROUND_ROBIN
  subsets:
    - name: v1
      labels:
        version: v1
    - name: v2
      labels:
        version: v2
      trafficPolicy:
        loadBalancer:
          simple: LEAST_REQUEST

# Canary deployment: gradually increase traffic to v2
apiVersion: networking.istio.io/v1
kind: VirtualService
metadata:
  name: my-service-canary
spec:
  hosts:
    - my-service
  http:
    - route:
        - destination:
            host: my-service
            subset: stable
          weight: 95
        - destination:
            host: my-service
            subset: canary
          weight: 5

# Gradual canary traffic increase script
# 5% → 10% → 25% → 50% → 100%
for weight in 10 25 50 100; do
  stable_weight=$((100 - weight))
  kubectl patch virtualservice my-service-canary --type=json \
    -p="[
      {\"op\":\"replace\",\"path\":\"/spec/http/0/route/0/weight\",\"value\":${stable_weight}},
      {\"op\":\"replace\",\"path\":\"/spec/http/0/route/1/weight\",\"value\":${weight}}
    ]"
  echo "Canary weight: ${weight}%, Stable weight: ${stable_weight}%"
  echo "Monitoring for 5 minutes..."
  sleep 300
done

# Circuit breaker via DestinationRule
apiVersion: networking.istio.io/v1
kind: DestinationRule
metadata:
  name: payment-service-cb
spec:
  host: payment-service
  trafficPolicy:
    connectionPool:
      tcp:
        maxConnections: 50
      http:
        http1MaxPendingRequests: 50
        http2MaxRequests: 100
        maxRequestsPerConnection: 10
        maxRetries: 3
    outlierDetection:
      consecutive5xxErrors: 5
      interval: 30s
      baseEjectionTime: 30s
      maxEjectionPercent: 50
      minHealthPercent: 30

# Check circuit breaker status
istioctl proxy-config cluster <pod-name> --fqdn payment-service.default.svc.cluster.local -o json | grep -A 20 "outlierDetection"

# Verify circuit breaker activity in Envoy stats
kubectl exec <pod-name> -c istio-proxy -- pilot-agent request GET stats | grep "circuit_breakers"

# Apply Strict mTLS to entire namespace
apiVersion: security.istio.io/v1
kind: PeerAuthentication
metadata:
  name: default
  namespace: default
spec:
  mtls:
    mode: STRICT
---
# Apply Strict mTLS mesh-wide (create in istio-system namespace)
apiVersion: security.istio.io/v1
kind: PeerAuthentication
metadata:
  name: default
  namespace: istio-system
spec:
  mtls:
    mode: STRICT

# PERMISSIVE mode for specific ports on a service
apiVersion: security.istio.io/v1
kind: PeerAuthentication
metadata:
  name: legacy-integration
  namespace: default
spec:
  selector:
    matchLabels:
      app: legacy-adapter
  mtls:
    mode: STRICT
  portLevelMtls:
    8080:
      mode: PERMISSIVE

# Check current mTLS status
istioctl authn tls-check <pod-name>

# View certificate information
istioctl proxy-config secret <pod-name> -o json

# SPIFFE ID format: spiffe://cluster.local/ns/NAMESPACE/sa/SERVICE_ACCOUNT
# Istio automatically assigns SPIFFE IDs based on Kubernetes service accounts

# Check certificate expiry (default 24h, auto-renewed)
kubectl exec <pod-name> -c istio-proxy -- \
  openssl x509 -noout -dates -in /var/run/secrets/istio/tls/cert-chain.pem

# Force certificate rotation (for debugging)
kubectl delete secret istio-ca-root-cert -n default
# Istiod will automatically issue new certificates

# Allow access only from specific services
apiVersion: security.istio.io/v1
kind: AuthorizationPolicy
metadata:
  name: payment-access
  namespace: default
spec:
  selector:
    matchLabels:
      app: payment-service
  rules:
    - from:
        - source:
            principals:
              - cluster.local/ns/default/sa/order-service
              - cluster.local/ns/default/sa/checkout-service
      to:
        - operation:
            methods: ['POST', 'GET']
            paths: ['/api/v1/payments/*']
---
# Deny all access (default deny policy)
apiVersion: security.istio.io/v1
kind: AuthorizationPolicy
metadata:
  name: deny-all
  namespace: default
spec: {}

# Install Istio with Ambient mode
istioctl install --set profile=ambient -y

# Add namespace to Ambient mesh
kubectl label namespace default istio.io/dataplane-mode=ambient

# Verify ztunnel DaemonSet
kubectl get pods -n istio-system -l app=ztunnel

# Deploy Waypoint proxy for L7 features
istioctl waypoint apply --namespace default --name default-waypoint

# Verify Waypoint proxy
kubectl get pods -n default -l istio.io/gateway-name=default-waypoint

# Sidecar mode:
#   Pros: Full L7 control, mature ecosystem
#   Cons: Per-pod proxy overhead, restart required
#   Resources: ~50MB RAM + ~0.5 vCPU / pod

# Ambient mode:
#   Pros: No pod restart needed, lower resource overhead
#   Cons: L7 requires waypoint, relatively newer technology
#   Resources: ztunnel ~30MB RAM / node + shared waypoint

# Selection criteria:
#   Migrating existing workloads → Consider Ambient first
#   Fine-grained L7 control needed → Keep Sidecar
#   Resource savings priority → Ambient
#   Stability priority → Sidecar (more mature)

# Install Kiali (Istio addon)
kubectl apply -f https://raw.githubusercontent.com/istio/istio/release-1.24/samples/addons/kiali.yaml

# Access Kiali dashboard
istioctl dashboard kiali

# Information Kiali provides:
# - Service-to-service traffic flow graph
# - Request success rate / error rate
# - P50/P90/P99 latency
# - mTLS status (lock icon)
# - Istio configuration validation (error highlighting)

# Install Jaeger
kubectl apply -f https://raw.githubusercontent.com/istio/istio/release-1.24/samples/addons/jaeger.yaml

# Access Jaeger dashboard
istioctl dashboard jaeger

# Applications MUST propagate trace headers upstream
# The following headers must be forwarded:
# x-request-id
# x-b3-traceid
# x-b3-spanid
# x-b3-parentspanid
# x-b3-sampled
# x-b3-flags
# traceparent
# tracestate

# Python Flask trace header propagation example
import requests
from flask import Flask, request

app = Flask(__name__)

TRACE_HEADERS = [
    'x-request-id',
    'x-b3-traceid',
    'x-b3-spanid',
    'x-b3-parentspanid',
    'x-b3-sampled',
    'x-b3-flags',
    'traceparent',
    'tracestate',
]

def propagate_headers():
    headers = {}
    for header in TRACE_HEADERS:
        value = request.headers.get(header)
        if value:
            headers[header] = value
    return headers

@app.route('/api/orders')
def get_orders():
    # Propagate trace headers when calling downstream services
    headers = propagate_headers()
    response = requests.get(
        'http://payment-service:8080/api/payments',
        headers=headers
    )
    return response.json()

# Install Prometheus and Grafana
kubectl apply -f https://raw.githubusercontent.com/istio/istio/release-1.24/samples/addons/prometheus.yaml
kubectl apply -f https://raw.githubusercontent.com/istio/istio/release-1.24/samples/addons/grafana.yaml

# Access Grafana dashboard
istioctl dashboard grafana

# Key metrics automatically collected by Istio:
# istio_requests_total          - Total request count
# istio_request_duration_milliseconds - Request latency
# istio_request_bytes           - Request size
# istio_response_bytes          - Response size
# istio_tcp_connections_opened_total - TCP connection count

# Example Prometheus queries
# Error rate by service (5xx)
# rate(istio_requests_total{response_code=~"5.."}[5m])
#   /
# rate(istio_requests_total[5m])

# P99 latency
# histogram_quantile(0.99,
#   sum(rate(istio_request_duration_milliseconds_bucket[5m]))
#   by (le, destination_service_name))

# Symptom: Pod is Running but sidecar (istio-proxy) is missing

# 1. Check namespace labels
kubectl get namespace default --show-labels
# Verify istio-injection=enabled label exists

# 2. Check container list in pod
kubectl get pod <pod-name> -o jsonpath='{.spec.containers[*].name}'
# If istio-proxy is not listed, injection failed

# 3. Diagnose root cause
# a. Missing namespace label
kubectl label namespace default istio-injection=enabled

# b. Pod has injection-disabled annotation
kubectl get pod <pod-name> -o jsonpath='{.metadata.annotations.sidecar\.istio\.io/inject}'
# "false" means injection is disabled

# c. Check webhook configuration
kubectl get mutatingwebhookconfiguration istio-sidecar-injector -o yaml

# 4. Manual injection (emergency)
istioctl kube-inject -f deployment.yaml | kubectl apply -f -

# 5. Restart pods (to apply injection)
kubectl rollout restart deployment <deployment-name>

# Symptom: Service-to-service communication failure, TLS handshake errors

# 1. Check certificate status
istioctl proxy-config secret <pod-name>
# Verify VALID status and expiry time

# 2. Check Istiod logs for certificate errors
kubectl logs -n istio-system deployment/istiod | grep -i "certificate\|cert\|error"

# 3. Verify CA certificate
kubectl get secret istio-ca-secret -n istio-system -o jsonpath='{.data.ca-cert\.pem}' | base64 -d | openssl x509 -noout -dates

# 4. Force certificate renewal
# Restart the pod's istio-proxy
kubectl delete pod <pod-name>

# 5. Restart Istiod (if CA issue)
kubectl rollout restart deployment istiod -n istio-system

# 6. Root CA rotation (planned operation)
# Create new Root CA and gradually transition via intermediate CA
# Refer to official CA rotation guide

# Symptom: istio-proxy container restarting with OOMKilled

# 1. Check current resource usage
kubectl top pod <pod-name> --containers

# 2. Check Envoy statistics
kubectl exec <pod-name> -c istio-proxy -- pilot-agent request GET stats/memory

# 3. Adjust resource limits
kubectl patch deployment <deployment-name> --type=json \
  -p='[{"op":"replace","path":"/spec/template/metadata/annotations/sidecar.istio.io~1proxyMemoryLimit","value":"512Mi"}]'

# 4. Global proxy resource settings (IstioOperator)
# Set in istio-operator.yaml:
# spec:
#   meshConfig:
#     defaultConfig:
#       proxyMetadata: {}
#   values:
#     global:
#       proxy:
#         resources:
#           requests:
#             cpu: 100m
#             memory: 128Mi
#           limits:
#             cpu: 500m
#             memory: 512Mi

# Scale Istiod replicas
kubectl scale deployment istiod -n istio-system --replicas=3

# Configure PDB
kubectl apply -f - <<ENDF
apiVersion: policy/v1
kind: PodDisruptionBudget
metadata:
  name: istiod-pdb
  namespace: istio-system
spec:
  minAvailable: 1
  selector:
    matchLabels:
      app: istiod
ENDF