本文使用istio版本：1.4.2

 Istio安装时，第一步就是创建了各种自定义资源类型（CRD），参考istio部署【在kubernetes上部署】，其中最重要的几个CRD包括：Gateway、VirtualService、DestinationRule、ServiceEntry。主要架构如下图：

Gateway充当入口服务，DestinationRule用于定义目标服务，VirtualService定义中间的路由。下面依次介绍。

DestinationRule

DestinationRule用于定义目标服务的访问策略，如在subset定义版本，定义负载均衡策略，熔断，一级TLS等。

基本示例

apiVersion: networking.istio.io/v1alpha3
kind: DestinationRule
metadata:
  name: reviews
spec:
  host: reviews
  subsets:
  - name: v1
    labels:
      version: v1
  - name: v2
    labels:
      version: v2

 定义负载均衡策略

apiVersion: networking.istio.io/v1alpha3
kind: DestinationRule
metadata:
  name: reviews
spec:
  host: reviews
  trafficPolicy:
    loadBalancer:
      simple: RANDOM
  subsets:
  - name: v1
    labels:
      version: v1
  - name: v2
    labels:
      version: v2
    trafficPolicy:
      loadBalancer:
        simple: ROUND_ROBIN

 定义熔断器

参考官网

apiVersion: networking.istio.io/v1alpha3
kind: DestinationRule
metadata:
  name: reviews
spec:
  host: reviews
  subsets:
  - name: v1
    labels:
      version: v1
    trafficPolicy:
      connectionPool:
        tcp:
          maxConnections: 100
      http:
        http1MaxPendingRequests: 100
        maxRequestsPerConnection: 100
    outlierDetection:
      consecutiveErrors: 1
      interval: 1s
      baseEjectionTime: 3m
      maxEjectionPercent: 100

VirtualService

VirtualService是最重要的配置接口，定义服务的所有路由规则，包括条件判断、权重、路径重写等。

定义权重示例

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: reviews
spec:
  hosts:
    - reviews
  http:
  - route:
    - destination:
        host: reviews
        subset: v1
      weight: 90
    - destination:
        host: reviews
        subset: v2
      weight: 10

定义超时和重试策略

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: ratings
spec:
  hosts:
    - ratings
  http:
  - route:
    - destination:
        host: ratings
        subset: v1
    timeout: 10s
    retries:
      attempts: 3
      perTryTimeout: 2s

故障注入：模拟失败的场景

参考Fault Injection

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: ratings
spec:
  hosts:
  - ratings
  http:
  - fault:
      #定义10%请求+5秒延迟， 也可以是percent: 10
      delay:
        percentage:
          value: 10
        fixedDelay: 5s

      #定义10%请求返回400错误， 也可以是percent: 10
      abort:
        percentage:
          value: 10
        httpStatus: 400
    route:
    - destination:
        host: ratings
        subset: v1

条件判断——标签

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: ratings
spec:
  hosts:
  - ratings
  http:
  - match:
    - sourceLabels:
        app: reviews
        version: v2
    ...

条件判断——Header

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: reviews
spec:
  hosts:
  - reviews
  http:
  - match:
    - headers:
        end-user:
          exact: jason
    route:
    - destination:
        host: reviews
        subset: v2

条件判断——URI路径

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: productpage
spec:
  hosts:
    - productpage
  http:
  - match:
    - uri:
        prefix: /api/v1
    ...

多条件判断

如果是嵌套在一个匹配语句中，为AND关系。

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: ratings
spec:
  hosts:
  - ratings
  http:
  - match:
    - sourceLabels:
        app: reviews
        version: v2
      headers:
        end-user:
          exact: jason
    ...

如果是单独的匹配语句，为OR关系。

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: ratings
spec:
  hosts:
  - ratings
  http:
  - match:
    - sourceLabels:
        app: reviews
        version: v2
    - headers:
        end-user:
          exact: jason
    ...

ServiceEntry

将外部服务接入到服务注册表中，让Istio中自动发现的服务能够访问和路由到这些手工加入的服务。与VirtualService或DestinationRule配合使用。

apiVersion: networking.istio.io/v1alpha3
kind: ServiceEntry
metadata:
  name: foo-ext-svc
spec:
  hosts:
  - *.foo.com
  ports:
  - number: 80
    name: http
    protocol: HTTP
  - number: 443
    name: https
    protocol: HTTPS

apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: bar-foo-ext-svc
spec:
  hosts:
    - bar.foo.com
  http:
  - route:
    - destination:
        host: bar.foo.com
    timeout: 10s

Gateway

提供外部服务访问接入，可发布任意内部端口的服务，供外部访问。配合VirtualService使用。

Bookinfo示例

apiVersion: networking.istio.io/v1alpha3
kind: Gateway
metadata:
  name: bookinfo-gateway
spec:
  selector:
    istio: ingressgateway # use istio default controller
  servers:
  - port:
      number: 80
      name: http
      protocol: HTTP
    hosts:
    - "*"
---
apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: bookinfo
spec:
  hosts:
  - "*"
  gateways:
  - bookinfo-gateway
  http:
  - match:
    - uri:
        exact: /productpage
    - uri:
        prefix: /static
    - uri:
        exact: /login
    - uri:
        exact: /logout
    - uri:
        prefix: /api/v1/products
    route:
    - destination:
        host: productpage
        port:
          number: 9080