Istio1.1.0下的TCP流量控制

2018年10月24日 | 作者 Venil Noronha | 译者 马若飞 | 审校者 宋净超 | 2400字 | 阅读大约需要5分钟
查看原文 | 归档于 translation | 标签 #istio

Istio通过虚拟服务, 目标规则, Gateway等概念提供了复杂的路由机制。Istio 1.0通过加权路由定义启用了HTTP流量转移。我提交的EnvoyIstio的pull request为TCP/TLS服务提供了类似的特性。这一特性已经在Envoy 1.8.0中发布了。Istio中的这一特性也会在即将发布的1.1.0版本中提供使用。

Istio

在本文中,我们将用Go编写的一个简单的TCP Echo服务,用Docker将其容器化并部署到Kubernetes上,并通过练习Istio的加权TCP路由特性来理解其在生产服务中的行为。

TCP Echo服务

在本文中,我们将创建一个简单的监听连接的TCP服务,并在客户端的请求数据加上一个简单的前缀,将其作为响应返回。图示如下:

TCP Client - Server Architecture

让我们看一下TCP Echo服务端的Go代码:

package main

import (
	"bufio"
	"fmt"
	"io"
	"net"
	"os"
)

// main作为程序入口点
func main() {
	// 通过程序入参获得端口和前缀
	port := fmt.Sprintf(":%s", os.Args[1])
	prefix := os.Args[2]

	// 在给定端口上创建tcp监听
	listener, err := net.Listen("tcp", port)
	if err != nil {
		fmt.Println("failed to create listener, err:", err)
		os.Exit(1)
	}
	fmt.Printf("listening on %s, prefix: %s\n", listener.Addr(), prefix)

	// 监听新的连接
	for {
		conn, err := listener.Accept()
		if err != nil {
			fmt.Println("failed to accept connection, err:", err)
			continue
		}

		// 启用goroutine处理连接
		go handleConnection(conn, prefix)
	}
}

// handleConnection 处理连接的生命周期
func handleConnection(conn net.Conn, prefix string) {
	defer conn.Close()
	reader := bufio.NewReader(conn)
	for {
		// 读取客户端请求数据
		bytes, err := reader.ReadBytes(byte('\n'))
		if err != nil {
			if err != io.EOF {
				fmt.Println("failed to read data, err:", err)
			}
			return
		}
		fmt.Printf("request: %s", bytes)

		// 添加前缀作为response返回
		line := fmt.Sprintf("%s %s", prefix, bytes)
		fmt.Printf("response: %s", line)
		conn.Write([]byte(line))
	}
}

要测试这个程序,复制上面代码并命名为main.go,执行命令如下:

$ go run -v main.go 9000 hello
listening on [::]:9000, prefix: hello

我们可以通过 nc (Netcat)在TCP层面上和这段程序交互。要发送请求,可以使用BusyBox容器,如下所示:

$ docker run -it --rm busybox sh -c 'echo world | nc docker.for.mac.localhost 9000'
hello world

就像你看到的,在请求“world”前面加上了“hello”,“hello world”作为响应。注意,正在执行的BusyBox容器基于 Docker for Mac,这就是为什么我访问Echo服务端时用docker.for.mac.localhost代替了localhost

容器化TCP Echo服务

因为我们最终想要在Kubernetes集群上运行TCP Echo服务,现在让我们将它容器化并发布镜像到 Docker Hub

首先,用下面的内容创建Dockerfile

# 使用golang容器构建可执行文件
FROM golang:1.11 as builder
WORKDIR /go/src/github.com/venilnoronha/tcp-echo-server/
COPY main.go .
RUN CGO_ENABLED=0 GOOS=linux go build -a -installsuffix cgo -o main main.go

# 负责bin文件到基于alpine的分离容器
FROM alpine:3.8
RUN apk --no-cache add ca-certificates
WORKDIR /bin/
COPY --from=builder /go/src/github.com/venilnoronha/tcp-echo-server/main .
ENTRYPOINT [ "/bin/main" ]
CMD [ "9000", "hello" ]
EXPOSE 9000

构建容器并发布镜像到Docker Hub:

$ docker build -t vnoronha/tcp-echo-server:latest .
Sending build context to Docker daemon  60.93kB
...
Successfully built d172af115e18
Successfully tagged vnoronha/tcp-echo-server:latest

$ docker push vnoronha/tcp-echo-server:latest
The push refers to repository [docker.io/vnoronha/tcp-echo-server]
b4cc76510de6: Pushed
...
latest: digest: sha256:0a45b5a0d362db6aa9154717ee3f2b... size: 949

部署TCP Echo服务到Kubernetes

服务配置

我们需要部署2个版本的TCP ECHO服务,用不同的前缀展示路由行为。创建service.yaml,用Kubernetes Service 和2个 Deployments 构建2个版本的TCP ECHO服务。

apiVersion: v1
kind: Service
metadata:
  name: tcp-echo-server
  labels:
    app: tcp-echo-server
    istio: ingressgateway # use istio default controller
spec:
  selector:
    app: tcp-echo-server
  ports:
  - port: 9000
    name: tcp
---
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: tcp-echo-server-v1
spec:
  replicas: 1
  template:
    metadata:
      labels:
        app: tcp-echo-server
        version: v1
    spec:
      containers:
      - name: tcp-echo-server
        image: vnoronha/tcp-echo-server:latest
        args: [ "9000", "one" ] # prefix: one
        imagePullPolicy: IfNotPresent
        ports:
        - containerPort: 9000
---
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: tcp-echo-server-v2
spec:
  replicas: 1
  template:
    metadata:
      labels:
        app: tcp-echo-server
        version: v2
    spec:
      containers:
      - name: tcp-echo-server
        image: vnoronha/tcp-echo-server:latest
        args: [ "9000", "two" ] # prefix: two
        imagePullPolicy: IfNotPresent
        ports:
        - containerPort: 9000

部署Minikube

Minikube是Kubernetes本地开发的最佳工具。用下面的命令启动Minikube实例:

$ minikube start --bootstrapper kubeadm       \
                 --memory=8192                \
                 --cpus=4                     \
                 --kubernetes-version=v1.10.0 \
                 --vm-driver=virtualbox
Starting local Kubernetes v1.10.0 cluster...
...
Kubectl is now configured to use the cluster.
Loading cached images from config file.

安装 Istio

在撰写本文时,Istio 1.1.0还没有发布。因此我使用了Istio的 Daily Pre-Release来演示这个新特性。请参考Istio文档学习下载和配置Istio。

一旦配置完成,这里有一个完全部署Istio组件的简单方法:

$ kubectl apply -f install/kubernetes/helm/istio/templates/crds.yaml
customresourcedefinition.apiextensions.k8s.io/virtualservices.networking.istio.io created
...
customresourcedefinition.apiextensions.k8s.io/templates.config.istio.io created
customresourcedefinition.apiextensions.k8s.io/handlers.config.istio.io created

$ kubectl apply -f install/kubernetes/istio-demo.yaml
namespace/istio-system created
...
destinationrule.networking.istio.io/istio-policy created
destinationrule.networking.istio.io/istio-telemetry created 

使用Istio代理部署TCP Echo服务

为了演示Istio的路由机制,我们以sidecar模式部署tcp-echo-server

$ kubectl apply -f <(istioctl kube-inject -f service.yaml)
service/tcp-echo-server created
deployment.extensions/tcp-echo-server-v1 created
deployment.extensions/tcp-echo-server-v2 created

通过下面的命令来验证服务运行:

$ kubectl get pods
NAME                                  READY     STATUS    RESTARTS   AGE
tcp-echo-server-v1-78684f5697-sv5r5   2/2       Running   0          56s
tcp-echo-server-v2-74bf9999c8-hhhf9   2/2       Running   0          56s

$ kubectl logs tcp-echo-server-v1-78684f5697-sv5r5 tcp-echo-server
listening on [::]:9000, prefix: one

$ kubectl logs tcp-echo-server-v2-74bf9999c8-hhhf9 tcp-echo-server
listening on [::]:9000, prefix: two

Istio加权TCP路由

这是本练习的最后一部分,定义VirtualServiceDestinationRule和带有权重路由的 Gateway,并验证系统行为。

路由配置

创建带有两个subsetDestinationRule来代表两个版本的 TCP Echo服务。Gateway 容许流量通过端口31400访问服务。最后,VirtualService限定了80%的流量必须被路由到TCP Echo服务的v1版本,20%被路由到v2版本。

apiVersion: networking.istio.io/v1alpha3
kind: DestinationRule
metadata:
  name: destination
spec:
  host: tcp-echo-server
  subsets:
  - name: v1
    labels:
      version: v1
  - name: v2
    labels:
      version: v2
---
apiVersion: networking.istio.io/v1alpha3
kind: Gateway
metadata:
  name: gateway
spec:
  selector:
    istio: ingressgateway
  servers:
  - port:
      number: 31400
      name: tcp
      protocol: TCP
    hosts:
    - "*"
---
apiVersion: networking.istio.io/v1alpha3
kind: VirtualService
metadata:
  name: route
spec:
  hosts:
  - "*"
  gateways:
  - gateway
  tcp:
  - match:
    - port: 31400
    route:
    - destination:
        host: tcp-echo-server
        port:
          number: 9000
        subset: v1
      weight: 80
    - destination:
        host: tcp-echo-server
        port:
          number: 9000
        subset: v2
      weight: 20

部署路由配置

为了让配置生效,复制上面的配置内容并创建文件route-config.yaml,用下面的命令进行安装:

kubectl apply -f route-config.yaml
destinationrule.networking.istio.io/destination created
gateway.networking.istio.io/gateway created
virtualservice.networking.istio.io/route created

验证Istio的TCP路由行为

先来确定一下Ingress的IP

$ minikube ip
192.168.99.100

现在可以通过Ingress发送一些请求到加权负载均衡的TCP Echo服务:

$ for i in {1..10}; do
for> docker run -it --rm busybox sh -c '(date; sleep 1) | nc 192.168.99.100 31400'
for> done
one Sat Oct 20 04:38:05 UTC 2018
two Sat Oct 20 04:38:07 UTC 2018
two Sat Oct 20 04:38:09 UTC 2018
one Sat Oct 20 04:38:12 UTC 2018
one Sat Oct 20 04:38:14 UTC 2018
one Sat Oct 20 04:38:17 UTC 2018
one Sat Oct 20 04:38:19 UTC 2018
one Sat Oct 20 04:38:22 UTC 2018
one Sat Oct 20 04:38:24 UTC 2018
two Sat Oct 20 04:38:27 UTC 2018

如你所见,大约80%的请求带有“one”前缀,剩下20%带有“two”前缀。这证明了加权TCP路由器确实生效了。

下图能让你很好地了解这个示范的情景:

Architecture

清理

只需要像下面一样删除Minikube的部署:

$ minikube stop && minikube delete
Stopping local Kubernetes cluster...
Machine stopped.
Deleting local Kubernetes cluster...
Machine deleted.

总结

如本文所示,即将发布的Istio 1.1.0版本配置加权TCP路由非常容易。本文提供了构建一个加权TCP路由的思路,让你学会如何从头开始控制TCP流量。