istio 访问网格内的服务(路由管理)

本文实验访问网络内的应用，并根据路由规则访问不同版本。
访问链路：istio-springboot-demo-a > istio-springboot-demo-b

一、应用准备

istio-springboot-demo-a 的代码如下：

@RestController
@RequestMapping("/test")
public class TestEndpoint {

    private RestTemplate restTemplate = new RestTemplate();

    @GetMapping("/request-b")
    public String requestb(@RequestParam("a") String a, @RequestParam(value = "forward", required = false) String forward) {
        String result = restTemplate.getForObject("http://" + forward + "/test/get?a=" + a, String.class);
        return PREFIX + " demo-a request " + forward + ": parameter a:" + a + "\n demo-b response:" + result;
    }
}
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istio-springboot-demo-b 分v1版本和latest版本，代码分别如下。
istio-springboot-demo-b:v1

@RestController
@RequestMapping("/test")
public class TestEndpoint {
    private static final String PREFIX = "Latest";

    @GetMapping("/get")
    public String get(@RequestParam("a") String a) {
        return PREFIX + " demo-b: test get and the parameter a is : " + a;
    }
}
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istio-springboot-demo-b:latest

@RestController
@RequestMapping("/test")
public class TestEndpoint {
    private static final String PREFIX = "V";

    @GetMapping("/get")
    public String get(@RequestParam("a") String a) {
        return PREFIX + " demo-b: test get and the parameter a is : " + a;
    }
}
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打包成镜像，具体方法参考：Java应用打包成Docker镜像

二、通过kubernetes Service访问

istio-springboot-demo-a 的部署过程参考 istio gateway入口流量路由管控

部署 istio-springbbot-demo-b

关于istio-springbbot-demo-b的部署过程也是类似的，创建部署istio-springbbot-demo-b需要的yaml文件，内含Service和Deployment。

demo-b-vault.yaml:

apiVersion: v1
kind: Service
metadata:
  name: istio-springboot-demo-b
  labels:
    app: istio-springboot-demo-b
    service: istio-springboot-demo-b
spec:
  ports:
  - name: http
    port: 80
    targetPort: 8081
  selector:
    app: istio-springboot-demo-b
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: istio-springboot-demo-b-v1
spec:
  replicas: 1
  selector:
    matchLabels:
      app: istio-springboot-demo-b
      version: v1
  template:
    metadata:
      labels:
        app: istio-springboot-demo-b
        version: v1
    spec:
      serviceAccountName: istio-demo    
      containers:
      - image: demo-istio-springboot-demo-b:1.0-SNAPSHOT
        imagePullPolicy: IfNotPresent
        name: istio-springboot-demo-b
        ports:
        - containerPort: 8081

---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: istio-springboot-demo-b-latest
spec:
  replicas: 1
  selector:
    matchLabels:
      app: istio-springboot-demo-b
      version: latest
  template:
    metadata:
      labels:
        app: istio-springboot-demo-b
        version: latest
    spec:
      serviceAccountName: istio-demo    
      containers:
      - image: demo-istio-springboot-demo-b:latest
        imagePullPolicy: IfNotPresent
        name: istio-springboot-demo-b
        ports:
        - containerPort: 8081
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执行kubectl 命令进行部署

kubectl apply -f demo-b-vault.yaml -n istio-demos
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访问 istio-springbbot-demo-b

本次实验通过istio-springboot-demo-a 访问网格内的istio-springboot-demo-b，没有配置istio的VirtualService，所以istio-springboot-demo-a 在访问istio-springboot-demo-b时，是随机路由istio-springboot-demo-b的两个版本。

访问url： http://demoa.istiodemos.com/test/request-b?forward=istio-springboot-demo-b.istio-demos.svc.cluster.local&a=av356

istio-springboot-demo-a和istio-springboot-demo-b是在同一个集群同一个namespace中，以下两个url也是一样可以访问的:

http://demoa.istiodemos.com/test/request-b?forward=istio-springboot-demo-b.istio-demos&a=av356

http://demoa.istiodemos.com/test/request-b?forward=istio-springboot-demo-b&a=av356
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三、制定路由规则

创建VirtualService，管理istio-springboot-demo-b的路由规则

istio的VirtualService是在kubernetes 的Service 之上新增的一层，主要负责路由、流控、降级等。

demo-b-route-virtualservice.yaml 的配置如下 :

apiVersion: networking.istio.io/v1alpha3
kind: DestinationRule
metadata:
  name: istio-springboot-demo-b-dr
spec:
  host: istio-springboot-demo-b
  trafficPolicy:
    loadBalancer:
        simple: LEAST_CONN
  subsets:
  - name: v1
    labels:
      version: v1
    trafficPolicy:
      loadBalancer:
        simple: ROUND_ROBIN
  - name: latest
    labels: 
      version: latest
---
apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: istio-springboot-demo-b-vs
spec:
  hosts:
  - "istio-springboot-demo-b"
  - "istio-springboot-demo-b.istio-demos"
  - "istio-springboot-demo-b.istio-demos.svc.cluster.local"
  http:
  - match:
    - queryParams:
        a:
          # exact: ad
          regex: ae\d+$
    route:
    - destination:
        host: istio-springboot-demo-b
        subset: v1
  - route:
    - destination:
        host: istio-springboot-demo-b
        subset: latest
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路由规则定义如下：

当queryString a 以ae加数字结尾(例如:ae32, fade32)时,路由到v1版本
否则都路由到latest版本
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执行kubectl 命令在kubernetes集群内创建VirtualService。

kubectl apply -f demo-b-route-virtualservice.yaml -n istio-demos
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访问 istio-springboot-demo-b 的不同版本

根据上面对istio-springboot-demo-b的路由规则定义：

当queryString a 以ae加数字结尾(例如:ae32, fade32)时,路由到v1版本
否则都路由到latest版本
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请求URL : http://demoa.istiodemos.com/test/request-b?forward=istio-springboot-demo-b&a=ae356 必定会被路由到istio-springboot-demo-b的v1版本。

请求URL : http://demoa.istiodemos.com/test/request-b?forward=istio-springboot-demo-b&a=ae356f 必定会被路由到istio-springboot-demo-b的latest版本。

接下来的实验也确实如下
http://demoa.istiodemos.com/test/request-b?forward=istio-springboot-demo-b&a=ae356:

http://demoa.istiodemos.com/test/request-b?forward=istio-springboot-demo-b&a=ae356f: