镜像

此任务演示了 Istio 的流量镜像功能。

流量镜像，也称为影子，是一个强大的概念，它允许功能团队以尽可能低的风险将更改引入生产环境。镜像会将实时流量的副本发送到镜像服务。镜像流量发生在主服务的关键请求路径之外。

在此任务中，您将首先强制所有流量到测试服务的 v1。然后，您将应用一个规则将部分流量镜像到 v2。

开始之前

1. 按照安装指南设置 Istio。

2. 首先部署两个启用了访问日志记录的httpbin服务版本。

   1. 部署httpbin-v1

      $ kubectl create -f - <<EOF
      apiVersion: apps/v1
      kind: Deployment
      metadata:
        name: httpbin-v1
      spec:
        replicas: 1
        selector:
          matchLabels:
            app: httpbin
            version: v1
        template:
          metadata:
            labels:
              app: httpbin
              version: v1
          spec:
            containers:
            - image: docker.io/kennethreitz/httpbin
              imagePullPolicy: IfNotPresent
              name: httpbin
              command: ["gunicorn", "--access-logfile", "-", "-b", "0.0.0.0:80", "httpbin:app"]
              ports:
              - containerPort: 80
      EOF
      

   2. 部署httpbin-v2

      $ kubectl create -f - <<EOF
      apiVersion: apps/v1
      kind: Deployment
      metadata:
        name: httpbin-v2
      spec:
        replicas: 1
        selector:
          matchLabels:
            app: httpbin
            version: v2
        template:
          metadata:
            labels:
              app: httpbin
              version: v2
          spec:
            containers:
            - image: docker.io/kennethreitz/httpbin
              imagePullPolicy: IfNotPresent
              name: httpbin
              command: ["gunicorn", "--access-logfile", "-", "-b", "0.0.0.0:80", "httpbin:app"]
              ports:
              - containerPort: 80
      EOF
      

   3. 部署httpbin Kubernetes 服务

      $ kubectl create -f - <<EOF
      apiVersion: v1
      kind: Service
      metadata:
        name: httpbin
        labels:
          app: httpbin
      spec:
        ports:
        - name: http
          port: 8000
          targetPort: 80
        selector:
          app: httpbin
      EOF
      

3. 部署您将用于向httpbin服务发送请求的curl工作负载。

   $ cat <<EOF | kubectl create -f -
   apiVersion: apps/v1
   kind: Deployment
   metadata:
     name: curl
   spec:
     replicas: 1
     selector:
       matchLabels:
         app: curl
     template:
       metadata:
         labels:
           app: curl
       spec:
         containers:
         - name: curl
           image: curlimages/curl
           command: ["/bin/sleep","3650d"]
           imagePullPolicy: IfNotPresent
   EOF
   

创建默认路由策略

默认情况下，Kubernetes 会在两个版本的httpbin服务之间进行负载均衡。在此步骤中，您将更改此行为，以便所有流量都转到v1。

1. 创建一个默认路由规则，将所有流量路由到服务的v1。

   Istio API Gateway API

   $ kubectl apply -f - <<EOF
   apiVersion: networking.istio.io/v1
   kind: VirtualService
   metadata:
     name: httpbin
   spec:
     hosts:
   - httpbin
     http:
     - route:
   - destination:
       host: httpbin
       subset: v1
     weight: 100
   ---
   apiVersion: networking.istio.io/v1
   kind: DestinationRule
   metadata:
     name: httpbin
   spec:
     host: httpbin
     subsets:
     - name: v1
   labels:
     version: v1
     - name: v2
   labels:
     version: v2
   EOF
   

2. 现在，所有流量都定向到httpbin:v1，向该服务发送请求。

   $ kubectl exec deploy/curl -c curl -- curl -sS http://httpbin:8000/headers
   {
     "headers": {
       "Accept": "*/*",
       "Content-Length": "0",
       "Host": "httpbin:8000",
       "User-Agent": "curl/7.35.0",
       "X-B3-Parentspanid": "57784f8bff90ae0b",
       "X-B3-Sampled": "1",
       "X-B3-Spanid": "3289ae7257c3f159",
       "X-B3-Traceid": "b56eebd279a76f0b57784f8bff90ae0b",
       "X-Envoy-Attempt-Count": "1",
       "X-Forwarded-Client-Cert": "By=spiffe://cluster.local/ns/default/sa/default;Hash=20afebed6da091c850264cc751b8c9306abac02993f80bdb76282237422bd098;Subject=\"\";URI=spiffe://cluster.local/ns/default/sa/default"
     }
   }
   

3. 检查来自httpbin-v1和httpbin-v2 Pod 的日志。您应该看到v1的访问日志条目，而v2没有。

   $ kubectl logs deploy/httpbin-v1 -c httpbin
   127.0.0.1 - - [07/Mar/2018:19:02:43 +0000] "GET /headers HTTP/1.1" 200 321 "-" "curl/7.35.0"
   

   $ kubectl logs deploy/httpbin-v2 -c httpbin
   <none>
   

将流量镜像到 httpbin-v2

1. 更改路由规则以将流量镜像到httpbin-v2。

   Istio API Gateway API

   $ kubectl apply -f - <<EOF
   apiVersion: networking.istio.io/v1
   kind: VirtualService
   metadata:
     name: httpbin
   spec:
     hosts:
   - httpbin
     http:
     - route:
   - destination:
       host: httpbin
       subset: v1
     weight: 100
   mirror:
     host: httpbin
     subset: v2
   mirrorPercentage:
     value: 100.0
   EOF
   

   此路由规则将 100% 的流量发送到v1。最后一段指定您希望镜像（即，也发送）100% 的相同流量到httpbin:v2服务。当流量被镜像时，请求将发送到镜像服务，其 Host/Authority 标头附加了-shadow。例如，cluster-1将变为cluster-1-shadow。

   此外，重要的是要注意，这些请求被镜像为“即发即弃”，这意味着响应会被丢弃。

   您可以使用mirrorPercentage字段下的value字段来镜像一部分流量，而不是镜像所有请求。如果此字段不存在，则会镜像所有流量。

2. 发送流量

   $ kubectl exec deploy/curl -c curl -- curl -sS http://httpbin:8000/headers
   

   现在，您应该看到v1和v2的访问日志。在v2中创建的访问日志实际上是发送到v1的镜像请求。

   $ kubectl logs deploy/httpbin-v1 -c httpbin
   127.0.0.1 - - [07/Mar/2018:19:02:43 +0000] "GET /headers HTTP/1.1" 200 321 "-" "curl/7.35.0"
   127.0.0.1 - - [07/Mar/2018:19:26:44 +0000] "GET /headers HTTP/1.1" 200 321 "-" "curl/7.35.0"
   

   $ kubectl logs deploy/httpbin-v2 -c httpbin
   127.0.0.1 - - [07/Mar/2018:19:26:44 +0000] "GET /headers HTTP/1.1" 200 361 "-" "curl/7.35.0"
   

清理

1. 删除规则

   Istio API Gateway API

   $ kubectl delete virtualservice httpbin
   $ kubectl delete destinationrule httpbin
   

2. 删除httpbin和curl部署以及httpbin服务

   $ kubectl delete deploy httpbin-v1 httpbin-v2 curl
   $ kubectl delete svc httpbin