Istio流量管理--Ingress Gateway

傳統上，Kubernetes使用Ingress控制器來處理從外部進入集羣的流量。使用Istio時，狀況再也不如此。 Istio已用新的Gateway和VirtualServices資源替換了熟悉的Ingress資源。它們協同工做，將流量路由到網格中。在網格內部，不須要Gateway，由於服務能夠經過集羣本地服務名稱相互訪問。

正如我以前文章介紹過的，kubernetes提供的Ingress過於簡單，暴露出來的屬性表達性太弱。固然社區也意識到了這個問題，從kubernetes1.19 版本，在逐步補全功能。Istio解決方案中，本身實現了Istio gateway。在非istio場景外，gloo，ambasaador ，contour等網關 能夠知足咱們生產環境的需求。

部署

咱們看下社區默認的部署。

經過Deployment管理的一組istio-ingressgateway Pod。

IngressGateway，這是Envoy代理的封裝。它的配置方式與服務網格中使用的Sidecar相同。當咱們建立或更改Gateway或VirtualService時，Istio Pilot控制器會檢測到更改，該控制器會將這些信息轉換爲Envoy配置並將其發送到相關代理，包括IngressGateway內部的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

咱們在IngressGateway部署中必須關心的是SSL證書。爲了可以訪問gateway資源中的證書，請確保已正確安裝了證書。

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

因爲istio-ingressgateway 主要處理邊界流量，因此必須建立LoadBalancer類型的service，全部外部流量都經過此雲負載均衡器進入集羣，該負載均衡器將流量路由到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

出於性能考慮，咱們應該講.spec.externalTrafficPolicy設置爲local模式，避免二跳。

其餘包括HPA，PDB以及RBAC等資源。

單集羣多Gateway

有時建立多個ingress gateway也頗有用。例如，在一個很是大的集羣中，有成千上萬的服務，您可能不想經過一個雲負載均衡器和一個部署來驅動全部外部流量，但但願水平分擔負載。

部署多個Gateway，比較簡單，參照上一步部署，注意更改一下命名，複製多個部署便可。

那咱們如何選擇ingress gateway那？經過selector選擇。以下：

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

配置

Ingress Gateway 不包含任何流量路由配置。Ingress 流量的路由使用 Istio 路由規則來配置，和內部服務請求徹底同樣。

讓咱們一塊兒來看如何爲 HTTP 流量在 80 端口上配置 Gateway。

1. 建立 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. 爲經過 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

已爲 httpbin 服務建立了虛擬服務配置，包含兩個路由規則，容許流量流向路徑 /status 和 /delay。

gateways 列表規約了哪些請求容許經過 httpbin-gateway 網關。 全部其餘外部請求均被拒絕並返回 404 響應。

安全性

使用 SDS 爲 Gateway 提供 HTTPS 加密支持

能夠配置 TLS Ingress Gateway ，讓它從 Ingress Gateway 代理經過 SDS 獲取憑據。Ingress Gateway 代理和 Ingress Gateway 在同一個 Pod 中運行，監視 Ingress Gateway 所在命名空間中新建的 Secret。在 Ingress Gateway 中啓用 SDS 具備以下好處：

• Ingress Gateway 無需重啓，就能夠動態的新增、刪除或者更新密鑰/證書對以及根證書。
• 無需加載 Secret 卷。建立了 kubernetes`Secret 以後，這個 Secret` 就會被 Gateway 代理捕獲，並以密鑰/證書對和根證書的形式發送給 Ingress Gateway 。
• Gateway 代理可以監視多個密鑰/證書對。只須要爲每一個主機名建立 Secret 並更新 Gateway 定義就能夠了。

無 TLS 終止的 Ingress Gateway

配置 Ingress Gateway 以執行 SNI 透傳，而不是對傳入請求進行 TLS 終止。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