Kubernetes微服务最佳实践：Podinfo演示插件使用指南

Podinfo是一个轻量级的Go微服务示例，专门设计用于演示Kubernetes最佳实践。下面我将详细介绍如何使用Podinfo以及相关的Golang代码示例。

1. Podinfo概述

Podinfo提供以下功能：

• HTTP和gRPC API端点
• 指标导出(Prometheus格式)
• 就绪/存活探针
• 混沌测试注入
• 配置管理
• 结构化日志记录

2. 部署Podinfo

基本部署YAML

apiVersion: apps/v1
kind: Deployment
metadata:
  name: podinfo
spec:
  replicas: 2
  selector:
    matchLabels:
      app: podinfo
  template:
    metadata:
      labels:
        app: podinfo
      annotations:
        prometheus.io/scrape: "true"
    spec:
      containers:
      - name: podinfo
        image: ghcr.io/stefanprodan/podinfo:latest
        imagePullPolicy: IfNotPresent
        ports:
        - containerPort: 9898
        env:
        - name: PODINFO_UI_COLOR
          value: "#34577c"
        resources:
          limits:
            cpu: 2000m
            memory: 512Mi
          requests:
            cpu: 100m
            memory: 64Mi
        livenessProbe:
          httpGet:
            path: /healthz
            port: 9898
          initialDelaySeconds: 5
          periodSeconds: 10
        readinessProbe:
          httpGet:
            path: /readyz
            port: 9898
          initialDelaySeconds: 5
          periodSeconds: 10

3. Golang客户端示例代码

HTTP客户端示例

package main

import (
	"context"
	"fmt"
	"io"
	"net/http"
	"time"
)

func main() {
	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
	defer cancel()

	req, err := http.NewRequestWithContext(ctx, "GET", "http://podinfo:9898", nil)
	if err != nil {
		panic(err)
	}

	resp, err := http.DefaultClient.Do(req)
	if err != nil {
		panic(err)
	}
	defer resp.Body.Close()

	body, err := io.ReadAll(resp.Body)
	if err != nil {
		panic(err)
	}

	fmt.Printf("Response: %s\n", body)
}

gRPC客户端示例

package main

import (
	"context"
	"log"
	"time"

	pb "github.com/stefanprodan/podinfo/pkg/api/grpc"
	"google.golang.org/grpc"
)

func main() {
	conn, err := grpc.Dial("podinfo:9999", grpc.WithInsecure())
	if err != nil {
		log.Fatalf("did not connect: %v", err)
	}
	defer conn.Close()

	c := pb.NewPodinfoClient(conn)

	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
	defer cancel()

	r, err := c.Status(ctx, &pb.StatusRequest{})
	if err != nil {
		log.Fatalf("could not get status: %v", err)
	}
	log.Printf("Status: %v", r)
}

4. 配置管理

Podinfo支持通过ConfigMap和环境变量配置：

package main

import (
	"log"
	"net/http"
	"os"
)

type Config struct {
	Color       string
	Message     string
	ServiceName string
}

func main() {
	cfg := Config{
		Color:       getEnv("PODINFO_UI_COLOR", "#34577c"),
		Message:     getEnv("PODINFO_UI_MESSAGE", "Welcome to Podinfo"),
		ServiceName: getEnv("PODINFO_SERVICE_NAME", "podinfo"),
	}

	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		w.Write([]byte(cfg.Message))
	})

	log.Fatal(http.ListenAndServe(":9898", nil))
}

func getEnv(key, fallback string) string {
	if value, ok := os.LookupEnv(key); ok {
		return value
	}
	return fallback
}

5. 健康检查实现

Podinfo的健康检查实现示例：

package main

import (
	"net/http"
	"sync/atomic"
)

var readiness int32

func main() {
	http.HandleFunc("/healthz", healthz)
	http.HandleFunc("/readyz", readyz)
	http.ListenAndServe(":9898", nil)
}

func healthz(w http.ResponseWriter, r *http.Request) {
	w.WriteHeader(http.StatusOK)
	w.Write([]byte("OK"))
}

func readyz(w http.ResponseWriter, r *http.Request) {
	if atomic.LoadInt32(&readiness) == 1 {
		w.WriteHeader(http.StatusOK)
		w.Write([]byte("OK"))
	} else {
		w.WriteHeader(http.StatusServiceUnavailable)
	}
}

// 在应用初始化完成后调用
func setReady() {
	atomic.StoreInt32(&readiness, 1)
}

6. 指标监控

使用Prometheus客户端库暴露指标：

package main

import (
	"net/http"

	"github.com/prometheus/client_golang/prometheus"
	"github.com/prometheus/client_golang/prometheus/promhttp"
)

var (
	requestsTotal = prometheus.NewCounterVec(
		prometheus.CounterOpts{
			Name: "http_requests_total",
			Help: "Total number of HTTP requests",
		},
		[]string{"method", "path", "status"},
	)
)

func init() {
	prometheus.MustRegister(requestsTotal)
}

func main() {
	http.Handle("/metrics", promhttp.Handler())
	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
		requestsTotal.WithLabelValues(r.Method, r.URL.Path, "200").Inc()
		w.Write([]byte("Hello World"))
	})
	http.ListenAndServe(":9898", nil)
}

7. 最佳实践总结

1. 资源限制：始终为容器设置资源请求和限制
2. 健康检查：实现存活和就绪探针
3. 配置分离：使用ConfigMap和Secret管理配置
4. 监控：暴露Prometheus格式的指标
5. 优雅终止：处理SIGTERM信号实现优雅关闭
6. 安全：使用非root用户运行容器
7. 日志：输出结构化日志
8. 滚动更新：配置适当的更新策略

Podinfo是一个优秀的Kubernetes微服务示例，展示了这些最佳实践的实际应用。通过研究其源代码和部署方式，可以学习到如何在Golang中构建生产就绪的Kubernetes微服务。