注：以下講述的按理環(huán)境場(chǎng)景是基于Kubernetes環(huán)境基礎(chǔ)上部署的Istio環(huán)境。

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涉及到Envoy概念介紹請(qǐng)參考深度解析Istio系列之流量控制篇。本文重點(diǎn)針對(duì)Envoy初始化場(chǎng)景進(jìn)行拆解。

Istio-proxy（Envoy）作為Istio數(shù)據(jù)平面的重要組件，基于sidecar方式與業(yè)務(wù)應(yīng)用混合部署到同一pod，為應(yīng)用提供代理服務(wù)。Pilot作為控制平面組件，基于元數(shù)據(jù)的抽象層，屏蔽底層具體容器環(huán)境（Kubernetes或者docker），同時(shí)為Envoy的策略執(zhí)行提供有效的數(shù)據(jù)支撐。那么Envoy如何獲取Pilot所在地址的信息呢？

下面通過(guò)官網(wǎng)BookInfo案例中Productpage服務(wù)的配置文件來(lái)說(shuō)明。

Pod容器說(shuō)明

執(zhí)行kubectl get deploy productpage-v1 -o yaml，獲取productpage部署模板，如下所示：

apiVersion: extensions/v1beta1

kind: Deployment

metadata:

  annotations:

    deployment.kubernetes.io/revision: "2"

    kubectl.kubernetes.io/last-applied-configuration: |

{"apiVersion":"extensions/v1beta1","kind":"Deployment","metadata":{"annotations":{},"creationTimestamp":null,"name":"productpage-v1","namespace":"default"},"spec":{"replicas":1,"strategy":{},"template":{"metadata":{"annotations":{"sidecar.istio.io/status":"{\"version\":\"50128f63e7b050c58e1cdce95b577358054109ad2aff4bc4995158c06924a43b\",\"initContainers\":[\"istio-init\"],\"containers\":[\"istio-proxy\"],\"volumes\":[\"istio-envoy\",\"istio-certs\"],\"imagePullSecrets\":null}"},"creationTimestamp":null,"labels":{"app":"productpage","version":"v1"}},"spec":{"containers":[{"image":"istio/examples-bookinfo-productpage-v1:1.8.0","imagePullPolicy":"IfNotPresent","name":"productpage","ports":[{"containerPort":9080}],"resources":{}},{"args":["proxy","sidecar","--configPath","/etc/istio/proxy","--binaryPath","/usr/local/bin/envoy","--serviceCluster","productpage","--drainDuration","45s","--parentShutdownDuration","1m0s","--discoveryAddress","istio-pilot.istio-system:15007","--discoveryRefreshDelay","1s","--zipkinAddress","zipkin.istio-system:9411","--connectTimeout","10s","--proxyAdminPort","15000","--controlPlaneAuthPolicy","NONE"],"env":[{"name":"POD_NAME","valueFrom":{"fieldRef":{"fieldPath":"metadata.name"}}},{"name":"POD_NAMESPACE","valueFrom":{"fieldRef":{"fieldPath":"metadata.namespace"}}},{"name":"INSTANCE_IP","valueFrom":{"fieldRef":{"fieldPath":"status.podIP"}}},{"name":"ISTIO_META_POD_NAME","valueFrom":{"fieldRef":{"fieldPath":"metadata.name"}}},{"name":"ISTIO_META_INTERCEPTION_MODE","value":"REDIRECT"},{"name":"ISTIO_METAJSON_LABELS","value":"{\"app\":\"productpage\",\"version\":\"v1\"}\n"}],"image":"docker.io/istio/proxyv2:1.0.5","imagePullPolicy":"IfNotPresent","name":"istio-proxy","ports":[{"containerPort":15090,"name":"http-envoy-prom","protocol":"TCP"}],"resources":{"requests":{"cpu":"10m"}},"securityContext":{"readOnlyRootFilesystem":true,"runAsUser":1337},"volumeMounts":[{"mountPath":"/etc/istio/proxy","name":"istio-envoy"},{"mountPath":"/etc/certs/","name":"istio-certs","readOnly":true}]}],"initContainers":[{"args":["-p","15001","-u","1337","-m","REDIRECT","-i","*","-x","","-b","9080","-d",""],"image":"docker.io/istio/proxy_init:1.0.5","imagePullPolicy":"IfNotPresent","name":"istio-init","resources":{},"securityContext":{"capabilities":{"add":["NET_ADMIN"]},"privileged":true}}],"volumes":[{"emptyDir":{"medium":"Memory"},"name":"istio-envoy"},{"name":"istio-certs","secret":{"optional":true,"secretName":"istio.default"}}]}}},"status":{}}

  creationTimestamp: 2018-12-18T01:51:18Z

  generation: 2

  labels:

    app: productpage

    version: v1

  name: productpage-v1

  namespace: default

  resourceVersion: "17402700"

  selfLink: /apis/extensions/v1beta1/namespaces/default/deployments/productpage-v1

  uid: 695ba22c-0267-11e9-8475-0050569c62d0

spec:

  progressDeadlineSeconds: 600

  replicas: 1

  revisionHistoryLimit: 10

  selector:

    matchLabels:

      app: productpage

      version: v1

  strategy:

    rollingUpdate:

      maxSurge: 1

      maxUnavailable: 1

    type: RollingUpdate

  template:

    metadata:

      annotations:

        sidecar.istio.io/status: '{"version":"50128f63e7b050c58e1cdce95b577358054109ad2aff4bc4995158c06924a43b","initContainers":["istio-init"],"containers":["istio-proxy"],"volumes":["istio-envoy","istio-certs"],"imagePullSecrets":null}'

      creationTimestamp: null

      labels:

        app: productpage

        version: v1

    spec:

      containers:

      - image: istio/examples-bookinfo-productpage-v1:1.8.0

        imagePullPolicy: IfNotPresent

        name: productpage

        ports:

        - containerPort: 9080

          protocol: TCP

        resources: {}

        terminationMessagePath: /dev/termination-log

        terminationMessagePolicy: File

      - args:

        - proxy

        - sidecar

        - --configPath

        - /etc/istio/proxy

        - --binaryPath

        - /usr/local/bin/envoy

        - --serviceCluster

        - productpage

        - --drainDuration

        - 45s

        - --parentShutdownDuration

        - 1m0s

        - --discoveryAddress

        - istio-pilot.istio-system:15007

        - --discoveryRefreshDelay

        - 1s

        - --zipkinAddress

        - zipkin.istio-system:9411

        - --connectTimeout

        - 10s

        - --proxyAdminPort

        - "15000"

        - --controlPlaneAuthPolicy

        - NONE

        env:

        - 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: ISTIO_META_POD_NAME

          valueFrom:

            fieldRef:

              apiVersion: v1

              fieldPath: metadata.name

        - name: ISTIO_META_INTERCEPTION_MODE

          value: REDIRECT

        - name: ISTIO_METAJSON_LABELS

          value: |

            {"app":"productpage","version":"v1"}

        image: docker.io/istio/proxyv2:1.0.5

        imagePullPolicy: IfNotPresent

        name: istio-proxy

        ports:

        - containerPort: 15090

          name: http-envoy-prom

          protocol: TCP

        resources:

          requests:

            cpu: 10m

        securityContext:

          readOnlyRootFilesystem: true

          runAsUser: 1337

        terminationMessagePath: /dev/termination-log

        terminationMessagePolicy: File

        volumeMounts:

        - mountPath: /etc/istio/proxy

          name: istio-envoy

        - mountPath: /etc/certs/

          name: istio-certs

          readOnly: true

      DNSPolicy: ClusterFirst

      initContainers:

      - args:

        - -p

        - "15001"

        - -u

        - "1337"

        - -m

        - REDIRECT

        - -i

        - '*'

        - -x

        - ""

        - -b

        - "9080"

        - -d

        - ""

        image: docker.io/istio/proxy_init:1.0.5

        imagePullPolicy: IfNotPresent

        name: istio-init

        resources: {}

        securityContext:

          capabilities:

            add:

            - NET_ADMIN

          privileged: true

        terminationMessagePath: /dev/termination-log

        terminationMessagePolicy: File

      restartPolicy: Always

      schedulerName: default-scheduler

      securityContext: {}

      terminationGracePeriodSeconds: 30

      volumes:

      - emptyDir:

          medium: Memory

        name: istio-envoy

      - name: istio-certs

        secret:

          defaultMode: 420

          optional: true

          secretName: istio.default

status:

  availableReplicas: 1

  conditions:

  - lastTransitionTime: 2018-12-18T01:51:19Z

    lastUpdateTime: 2018-12-18T01:51:19Z

    message: Deployment has minimum availability.

    reason: MinimumReplicasAvailable

    status: "True"

    type: Available

  - lastTransitionTime: 2018-12-18T01:51:18Z

    lastUpdateTime: 2018-12-18T03:48:52Z

    message: ReplicaSet "productpage-v1-7b96bbf89f" has successfully progressed.

    reason: NewReplicaSetAvailable

    status: "True"

    type: Progressing

  observedGeneration: 2

  readyReplicas: 1

  replicas: 1

  updatedReplicas: 1

模板中可見(jiàn)，除業(yè)務(wù)應(yīng)用外，還包括istio-init，istio-proxy兩個(gè)容器。istio-init作為Init Container類型，在應(yīng)用容器啟動(dòng)之前啟動(dòng)，用來(lái)執(zhí)行初始化任務(wù)。Istio-init主要初始化iptables規(guī)則，用于服務(wù)間調(diào)用時(shí)的請(qǐng)求攔截及轉(zhuǎn)發(fā)。Istio-proxy是代理容器（即Envoy），容器中包含兩個(gè)進(jìn)程，分別是Pilot-agent進(jìn)程和Envoy進(jìn)程。前者負(fù)責(zé)生成Envoy啟動(dòng)所需的配置文件，啟動(dòng)Envoy進(jìn)程。后者在服務(wù)調(diào)用發(fā)生時(shí)負(fù)責(zé)具體的策略執(zhí)行。

Envoy配置信息詳解

Envoy啟動(dòng)后，執(zhí)行kubectl exec -it productpage-v1-7b96bbf89f-pj28l -c istio-proxy /bin/sh，進(jìn)入istio-proxy容器內(nèi)部，在/etc/istio/proxy目錄下存在envoy-rev0.json配置文件，如圖2所示：

該文件是Pilot是Pilot-agent進(jìn)程根據(jù)服務(wù)啟動(dòng)參數(shù)以及Kubernetes Server API的信息生成，配置文件框架如圖3所示：

Node包含的信息如圖4所示：

這里重點(diǎn)說(shuō)明cluster屬性，該屬性值為productpage，說(shuō)明當(dāng)前的istio-proxy服務(wù)為productpage應(yīng)用的代理服務(wù)，iptables將調(diào)用productpage服務(wù)請(qǐng)求攔截后，直接轉(zhuǎn)發(fā)到該istio-proxy進(jìn)行處理。

stats_config包含的信息如圖5所示：

static_config重點(diǎn)設(shè)定部分屬性的命名規(guī)則。

admin包含的信息如圖6所示：

admin類似Envoy內(nèi)部的一個(gè)管理器，暴露出的15000端口只能在容器內(nèi)部被訪問(wèn)。

通過(guò)curl http://127.0.0.1:15000/help訪問(wèn)能獲取其他接口信息，如下圖7所示：

dynamic_resources包含的信息如圖8所示：

dynamic_resources中記錄pilot調(diào)取XDS接口采用ADS聚合發(fā)現(xiàn)服務(wù)，這種方式能更好的保證從pilot上獲取到的數(shù)據(jù)的一致性。

static_resources包含的部分信息如圖9所示：

static_resources name屬性值為xds-grpc，與上述dynamic_resources模塊的信息里cluster_name的值一致。同時(shí)xds-grpc對(duì)象信息中包括pilot組件的服務(wù)地址“istio-pilot.istio-system:15010”，即為istio-proxy從pilot獲取動(dòng)態(tài)信息的服務(wù)地址。Istio-proxy（Envoy）通過(guò)該地址調(diào)取XDS接口，獲取服務(wù)信息。除此之外，static_resources中提供zipkin服務(wù)的地址，zipkin是用于服務(wù)分布式跟蹤。

綜上可知Envoy啟動(dòng)時(shí)，pilot-agent進(jìn)程生成Envoy啟動(dòng)所需的配置文件，Envoy基于配置文件中攜帶的pilot地址信息動(dòng)態(tài)獲取服務(wù)信息，并且基于pilot提供的XDS接口，動(dòng)態(tài)獲取服務(wù)的listener，cluster，endpoint和route信息。