ISTIO 出口网关流程答案

【问题标题】：ISTIO Egress gateway FlowISTIO 出口网关流程
【发布时间】：2020-10-24 13:10:17
【问题描述】：

我已经使用以下配置安装了 ISTIO

cat << EOF | kubectl apply -f -
apiVersion: install.istio.io/v1alpha1
kind: IstioOperator
metadata:
  namespace: istio-system
  name: istio-control-plane
spec:
  # Use the default profile as the base
  # More details at: https://istio.io/docs/setup/additional-setup/config-profiles/
  profile: default
  # Enable the addons that we will want to use
  addonComponents:
    grafana:
      enabled: true
    prometheus:
      enabled: true
    tracing:
      enabled: true
    kiali:
      enabled: true
  values:
    global:
      # Ensure that the Istio pods are only scheduled to run on Linux nodes
      defaultNodeSelector:
        beta.kubernetes.io/os: linux
    kiali:
      dashboard:
        auth:
          strategy: anonymous
  components:
    egressGateways:
    - name: istio-egressgateway
      enabled: true
  meshConfig:
    accessLogFile: /dev/stdout
    outboundTrafficPolicy:
      mode: REGISTRY_ONLY
EOF

并已配置 Egress Gateway、Destination Rule 和 Virtual Service，如下所示

cat << EOF | kubectl apply -f -
apiVersion: v1
kind: Namespace
metadata:
  name: akv2k8s-test
  labels:
    istio-injection: enabled
    azure-key-vault-env-injection: enabled
---
apiVersion: networking.istio.io/v1alpha3
kind: ServiceEntry
metadata:
  name: cnn
  namespace: akv2k8s-test
spec:
  hosts:
  - edition.cnn.com
  ports:
  - number: 80
    name: http-port
    protocol: HTTP
  - number: 443
    name: https
    protocol: HTTPS
  resolution: DNS
---
apiVersion: networking.istio.io/v1alpha3
kind: Gateway
metadata:
  name: istio-egressgateway
  namespace: akv2k8s-test
spec:
  selector:
    istio: egressgateway
  servers:
  - port:
      number: 80
      name: http
      protocol: HTTP
    hosts:
    - edition.cnn.com
---
apiVersion: networking.istio.io/v1alpha3
kind: DestinationRule
metadata:
  name: egressgateway-for-cnn
  namespace: akv2k8s-test
spec:
  host: istio-egressgateway.istio-system.svc.cluster.local
  subsets:
  - name: cnn
---
apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: direct-cnn-through-egress-gateway
  namespace: akv2k8s-test
spec:
  hosts:
  - edition.cnn.com
  gateways:
  - istio-egressgateway
  - mesh
  http:
  - match:
    - gateways:
      - mesh
      port: 80
    route:
    - destination:
        host: istio-egressgateway.istio-system.svc.cluster.local
        subset: cnn
        port:
          number: 80
      weight: 100
  - match:
    - gateways:
      - istio-egressgateway
      port: 80
    route:
    - destination:
        host: edition.cnn.com
        port:
          number: 80
      weight: 100
EOF

一切正常

kubectl apply -f https://raw.githubusercontent.com/istio/istio/release-1.7/samples/sleep/sleep.yaml -n akv2k8s-test
export SOURCE_POD=$(kubectl get pod -l app=sleep -n akv2k8s-test -o jsonpath={.items..metadata.name})
kubectl exec "$SOURCE_POD" -n akv2k8s-test -c sleep -- curl -sL -o /dev/null -D - http://edition.cnn.com/politics
kubectl logs -l istio=egressgateway -c istio-proxy -n istio-system | tail

但是我无法理解控制流程。例如下图是Ingress Gateway的控制流程

能否告诉我 ISTIO Egress 的控制流程？或者当部署的应用程序尝试访问外部服务时会发生什么？是否遵循流程：POD -> 代理 -> 虚拟服务 -> 目标规则 -> 网关 -> 外部服务？

【问题讨论】：

标签： kubernetes istio istio-sidecar

【解决方案1】：

是的，你的猜测是正确的。

流程是POD > envoy proxy > Gateway > Eternal Service

当流量从应用容器发出时，会被 envoy 代理 sidecar 拦截并应用 envoy 过滤器。

envoy 过滤器链由VirtualService 和DestinationRule 对象生成，可以使用istioctl proxy-config 命令检查。

【讨论】：