关于istio:Istio流量管理Ingress-Gateway

传统上，Kubernetes 应用 Ingress 控制器来解决从内部进入集群的流量。应用 Istio 时，状况不再如此。Istio 已用新的 Gateway 和VirtualServices资源替换了相熟的 Ingress 资源。它们协同工作，将流量路由到网格中。在网格外部，不须要Gateway，因为服务能够通过集群本地服务名称互相拜访。

正如我之前文章介绍过的，kubernetes 提供的 Ingress 过于简略，裸露进去的属性表白性太弱。当然社区也意识到了这个问题，从 kubernetes1.19 版本，在逐渐补全性能。Istio 解决方案中，本人实现了 Istio gateway。在非 istio 场景外，gloo，ambasaador，contour 等网关 能够满足咱们生产环境的需要。

部署

咱们看下社区默认的部署。

通过 Deployment 治理的一组istio-ingressgateway Pod。

IngressGateway，这是 Envoy 代理的封装。它的配置形式与服务网格中应用的 Sidecar 雷同。当咱们创立或更改 Gateway 或 VirtualService 时，Istio Pilot 控制器会检测到更改，该控制器会将这些信息转换为 Envoy 配置并将其发送到相干代理，包含 IngressGateway 外部的 Envoy。

apiVersion: apps/v1
kind: Deployment
metadata:
  labels:
    app: istio-ingressgateway
    istio: ingressgateway
    release: istio
  name: istio-ingressgateway
  namespace: istio-system
spec:
  selector:
    matchLabels:
      app: istio-ingressgateway
      istio: ingressgateway
  strategy:
    rollingUpdate:
      maxSurge: 100%
      maxUnavailable: 25%
  template:
    metadata:
      annotations:
        prometheus.io/path: /stats/prometheus
        prometheus.io/port: "15090"
        prometheus.io/scrape: "true"
        sidecar.istio.io/inject: "false"
      labels:
        app: istio-ingressgateway
        chart: gateways
        heritage: Tiller
        istio: ingressgateway
        release: istio
        service.istio.io/canonical-name: istio-ingressgateway
        service.istio.io/canonical-revision: latest
    spec:
      affinity:
        nodeAffinity:
          preferredDuringSchedulingIgnoredDuringExecution:
          - preference:
              matchExpressions:
              - key: kubernetes.io/arch
                operator: In
                values:
                - amd64
            weight: 2
          - preference:
              matchExpressions:
              - key: kubernetes.io/arch
                operator: In
                values:
                - ppc64le
            weight: 2
          - preference:
              matchExpressions:
              - key: kubernetes.io/arch
                operator: In
                values:
                - s390x
            weight: 2
          requiredDuringSchedulingIgnoredDuringExecution:
            nodeSelectorTerms:
            - matchExpressions:
              - key: kubernetes.io/arch
                operator: In
                values:
                - amd64
                - ppc64le
                - s390x
      containers:
      - args:
        - proxy
        - router
        - --domain
        - $(POD_NAMESPACE).svc.cluster.local
        - --proxyLogLevel=warning
        - --proxyComponentLogLevel=misc:error
        - --log_output_level=default:info
        - --serviceCluster
        - istio-ingressgateway
        - --trust-domain=cluster.local
        env:
        - name: JWT_POLICY
          value: third-party-jwt
        - name: PILOT_CERT_PROVIDER
          value: istiod
        - name: CA_ADDR
          value: istiod.istio-system.svc:15012
        - name: NODE_NAME
          valueFrom:
            fieldRef:
              apiVersion: v1
              fieldPath: spec.nodeName
        - name: POD_NAME
          valueFrom:
            fieldRef:
              apiVersion: v1
              fieldPath: metadata.name
        - name: POD_NAMESPACE
          valueFrom:
            fieldRef:
              apiVersion: v1
              fieldPath: metadata.namespace
        - name: INSTANCE_IP
          valueFrom:
            fieldRef:
              apiVersion: v1
              fieldPath: status.podIP
        - name: HOST_IP
          valueFrom:
            fieldRef:
              apiVersion: v1
              fieldPath: status.hostIP
        - name: SERVICE_ACCOUNT
          valueFrom:
            fieldRef:
              fieldPath: spec.serviceAccountName
        - name: CANONICAL_SERVICE
          valueFrom:
            fieldRef:
              fieldPath: metadata.labels['service.istio.io/canonical-name']
        - name: CANONICAL_REVISION
          valueFrom:
            fieldRef:
              fieldPath: metadata.labels['service.istio.io/canonical-revision']
        - name: ISTIO_META_WORKLOAD_NAME
          value: istio-ingressgateway
        - name: ISTIO_META_OWNER
          value: kubernetes://apis/apps/v1/namespaces/istio-system/deployments/istio-ingressgateway
        - name: ISTIO_META_MESH_ID
          value: cluster.local
        - name: ISTIO_META_ROUTER_MODE
          value: sni-dnat
        - name: ISTIO_META_CLUSTER_ID
          value: Kubernetes
        image: docker.io/istio/proxyv2:1.7.3
        name: istio-proxy
        ports:
        - containerPort: 15021
        - containerPort: 8080
        - containerPort: 8443
        - containerPort: 15443
        - containerPort: 15090
          name: http-envoy-prom
          protocol: TCP
        readinessProbe:
          failureThreshold: 30
          httpGet:
            path: /healthz/ready
            port: 15021
            scheme: HTTP
          initialDelaySeconds: 1
          periodSeconds: 2
          successThreshold: 1
          timeoutSeconds: 1
        resources:
          limits:
            cpu: 2000m
            memory: 1024Mi
          requests:
            cpu: 100m
            memory: 128Mi
        securityContext:
          allowPrivilegeEscalation: false
          capabilities:
            drop:
            - ALL
          privileged: false
          readOnlyRootFilesystem: true
        volumeMounts:
        - mountPath: /etc/istio/proxy
          name: istio-envoy
        - mountPath: /etc/istio/config
          name: config-volume
        - mountPath: /var/run/secrets/istio
          name: istiod-ca-cert
        - mountPath: /var/run/secrets/tokens
          name: istio-token
          readOnly: true
        - mountPath: /var/run/ingress_gateway
          name: gatewaysdsudspath
        - mountPath: /etc/istio/pod
          name: podinfo
        - mountPath: /etc/istio/ingressgateway-certs
          name: ingressgateway-certs
          readOnly: true
        - mountPath: /etc/istio/ingressgateway-ca-certs
          name: ingressgateway-ca-certs
          readOnly: true
      securityContext:
        fsGroup: 1337
        runAsGroup: 1337
        runAsNonRoot: true
        runAsUser: 1337
      serviceAccountName: istio-ingressgateway-service-account
      volumes:
      - configMap:
          name: istio-ca-root-cert
        name: istiod-ca-cert
      - downwardAPI:
          items:
          - fieldRef:
              fieldPath: metadata.labels
            path: labels
          - fieldRef:
              fieldPath: metadata.annotations
            path: annotations
        name: podinfo
      - emptyDir: {}
        name: istio-envoy
      - emptyDir: {}
        name: gatewaysdsudspath
      - name: istio-token
        projected:
          sources:
          - serviceAccountToken:
              audience: istio-ca
              expirationSeconds: 43200
              path: istio-token
      - configMap:
          name: istio
          optional: true
        name: config-volume
      - name: ingressgateway-certs
        secret:
          optional: true
          secretName: istio-ingressgateway-certs
      - name: ingressgateway-ca-certs
        secret:
          optional: true
          secretName: istio-ingressgateway-ca-certs

咱们在 IngressGateway 部署中必须关怀的是 SSL 证书。为了可能拜访 gateway 资源中的证书，请确保已正确装置了证书。

 volumeMounts:
        - mountPath: /etc/istio/ingressgateway-certs
          name: ingressgateway-certs
          readOnly: true
        - mountPath: /etc/istio/ingressgateway-ca-certs
          name: ingressgateway-ca-certs
          readOnly: true
     
      volumes:
      - name: ingressgateway-certs
        secret:
          optional: true
          secretName: istio-ingressgateway-certs
      - name: ingressgateway-ca-certs
        secret:
          optional: true
          secretName: istio-ingressgateway-ca-certs 

因为 istio-ingressgateway 次要解决边界流量，所以必须创立 LoadBalancer 类型的 service，所有内部流量都通过此云负载均衡器进入集群，该负载均衡器将流量路由到istio-ingressgateway 的 envoy 容器。

apiVersion: v1
kind: Service
metadata:
  labels:
    app: istio-ingressgateway
    istio: ingressgateway
    release: istio
  name: istio-ingressgateway
  namespace: istio-system
spec:
  ports:
  - name: status-port
    port: 15021
    targetPort: 15021
  - name: http2
    port: 80
    targetPort: 8080
  - name: https
    port: 443
    targetPort: 8443
  - name: tls
    port: 15443
    targetPort: 15443
  selector:
    app: istio-ingressgateway
    istio: ingressgateway
  type: LoadBalancer

出于性能思考，咱们应该讲.spec.externalTrafficPolicy 设置为 local 模式，防止二跳。

其余包含 HPA，PDB 以及 RBAC 等资源。

单集群多 Gateway

有时创立多个 ingress gateway 也很有用。例如，在一个十分大的集群中，有成千上万的服务，您可能不想通过一个云负载均衡器和一个部署来驱动所有内部流量，但心愿程度分担负载。

部署多个 Gateway，比较简单，参照上一步部署，留神更改一下命名，复制多个部署即可。

那咱们如何抉择 ingress gateway 那？通过 selector 抉择。如下：

metadata:
  name: gateway
spec:
  selector:
    istio: second-istio-ingressgateway

配置

Ingress Gateway 不蕴含任何流量路由配置。Ingress 流量的路由应用 Istio 路由规定来配置，和外部服务申请齐全一样。

让咱们一起来看如何为 HTTP 流量在 80 端口上配置 Gateway。

1. 创立 Istio Gateway：

$ kubectl apply -f - <<EOF
apiVersion: networking.istio.io/v1alpha3
kind: Gateway
metadata:
  name: httpbin-gateway
spec:
  selector:
    istio: ingressgateway # use Istio default gateway implementation
  servers:
  - port:
      number: 80
      name: http
      protocol: HTTP
    hosts:
    - "httpbin.example.com"
EOF

1. 为通过 Gateway 的入口流量配置路由：

$ kubectl apply -f - <<EOF
apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: httpbin
spec:
  hosts:
  - "httpbin.example.com"
  gateways:
  - httpbin-gateway
  http:
  - match:
    - uri:
        prefix: /status
    - uri:
        prefix: /delay
    route:
    - destination:
        port:
          number: 8000
        host: httpbin
EOF

已为 httpbin 服务创立了虚构服务配置，蕴含两个路由规定，容许流量流向门路 /status 和 /delay。

gateways 列表规约了哪些申请容许通过 httpbin-gateway 网关。所有其余内部申请均被回绝并返回 404 响应。

安全性

应用 SDS 为 Gateway 提供 HTTPS 加密反对

能够配置 TLS Ingress Gateway，让它从 Ingress Gateway 代理通过 SDS 获取凭据。Ingress Gateway 代理和 Ingress Gateway 在同一个 Pod 中运行，监督 Ingress Gateway 所在命名空间中新建的 Secret。在 Ingress Gateway 中启用 SDS 具备如下益处：

• Ingress Gateway 无需重启，就能够动静的新增、删除或者更新密钥 / 证书对以及根证书。
• 无需加载 Secret 卷。创立了 kubernetes`Secret 之后，这个 Secret` 就会被 Gateway 代理捕捉，并以密钥 / 证书对和根证书的模式发送给 Ingress Gateway。
• Gateway 代理可能监督多个密钥 / 证书对。只须要为每个主机名创立 Secret 并更新 Gateway 定义就能够了。

无 TLS 终止的 Ingress Gateway

配置 Ingress Gateway 以执行 SNI 透传，而不是对传入申请进行 TLS 终止。例如：

apiVersion: networking.istio.io/v1alpha3
kind: Gateway
metadata:
  name: mygateway
spec:
  selector:
    istio: ingressgateway # use istio default ingress gateway
  servers:
  - port:
      number: 443
      name: https
      protocol: HTTPS
    tls:
      mode: PASSTHROUGH
    hosts:
    - nginx.example.com