gRPC服務健康檢查（一）：Golang項目內建服務健康檢查代碼

gRPC服務健康檢查（Health Checking）

健康檢查用來檢測gRPC服務是否可以處理rpc請求，gRPC官方有專門的健康檢查協定，官方也根據協定實作了相關的邏輯代碼，gRPC項目可以很友善得內建。接下來就講解一下gRPC項目內建健康檢查代碼的方法。

gRPC服務內建健康檢查代碼的方法

首先需要定義健康檢查服務的名稱，因為健康檢查本身也是一個gRPC服務，一般情況下使用grpc.health.v1.Health即可：

const healthCheckService = "grpc.health.v1.Health"           

然後需要導入以下幾個關鍵的包：

import (
    "google.golang.org/grpc"
    "google.golang.org/grpc/health"
    healthpb "google.golang.org/grpc/health/grpc_health_v1"
)           

注冊健康檢查服務：

s := grpc.NewServer()

// 注冊健康檢查server
healthCheckServer := health.NewServer()
healthCheckServer.SetServingStatus(healthCheckService, healthpb.HealthCheckResponse_SERVING)
healthpb.RegisterHealthServer(s, healthCheckServer)           

這樣就完成內建工作了，很簡單吧？

完整代碼如下，以gRPC官方的helloworld服務為例（下面的代碼可以直接運作）：

package main

import (
	"context"
	"flag"
	"fmt"
	"log"
	"net"

	"google.golang.org/grpc"
	pb "google.golang.org/grpc/examples/helloworld/helloworld"
	"google.golang.org/grpc/health"
	healthpb "google.golang.org/grpc/health/grpc_health_v1"
)

var (
	port = flag.Int("port", 50051, "The server port")
)

const healthCheckService = "grpc.health.v1.Health"

// server is used to implement helloworld.GreeterServer.
type server struct {
	pb.UnimplementedGreeterServer
}

// SayHello implements helloworld.GreeterServer
func (s *server) SayHello(ctx context.Context, in *pb.HelloRequest) (*pb.HelloReply, error) {
	log.Printf("Received: %v", in.GetName())
	return &pb.HelloReply{Message: "Hello " + in.GetName()}, nil
}

func main() {
	flag.Parse()
	lis, err := net.Listen("tcp", fmt.Sprintf(":%d", *port))
	if err != nil {
		log.Fatalf("failed to listen: %v", err)
	}
	s := grpc.NewServer()
	// register業務server
	pb.RegisterGreeterServer(s, &server{})
	// register健康檢查server
	// health check server
	healthCheckServer := health.NewServer()
	healthCheckServer.SetServingStatus(healthCheckService, healthpb.HealthCheckResponse_SERVING)
	healthpb.RegisterHealthServer(s, healthCheckServer)

	log.Printf("server listening at %v", lis.Addr())
	if err := s.Serve(lis); err != nil {
		log.Fatalf("failed to serve: %v", err)
	}
}
           

gRPC用戶端內建健康檢查代碼

需要導入以下幾個關鍵的包：

import(
    "google.golang.org/grpc"
    _ "google.golang.org/grpc/health"
)           

grpc.Dial() 方法添加對應參數：

conn, err := grpc.Dial(
		*addr,
		grpc.WithTransportCredentials(insecure.NewCredentials()),
		grpc.WithDefaultServiceConfig(fmt.Sprintf(`{"HealthCheckConfig": {"ServiceName": "%s"}}`, healthCheckService)),
	)           

完整代碼如下，以gRPC官方的helloworld為例（下面的代碼可以直接運作）：

package main

import (
	"context"
	"flag"
	"fmt"
	"log"
	"time"

	"google.golang.org/grpc"
	"google.golang.org/grpc/credentials/insecure"
	pb "google.golang.org/grpc/examples/helloworld/helloworld"
	_ "google.golang.org/grpc/health"
)

const (
	defaultName        = "world"
	healthCheckService = "grpc.health.v1.Health"
)

var (
	addr = flag.String("addr", "localhost:50051", "the address to connect to")
	name = flag.String("name", defaultName, "Name to greet")
)

func main() {
	flag.Parse()
	// Set up a connection to the server.
	conn, err := grpc.Dial(
		*addr,
		grpc.WithTransportCredentials(insecure.NewCredentials()),
		grpc.WithDefaultServiceConfig(fmt.Sprintf(`{"HealthCheckConfig": {"ServiceName": "%s"}}`, healthCheckService)),
	)
	if err != nil {
		log.Fatalf("did not connect: %v", err)
	}
	defer conn.Close()
	c := pb.NewGreeterClient(conn)

	// Contact the server and print out its response.
	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
	defer cancel()
	r, err := c.SayHello(ctx, &pb.HelloRequest{Name: *name})
	if err != nil {
		log.Fatalf("could not greet: %v", err)
	}
	log.Printf("Greeting: %s", r.GetMessage())
}
           

使用grpc-health-probe工具進行健康檢查

安裝grpc-health-probe：

go install github.com/grpc-ecosystem/grpc-health-probe@latest           

安裝完成後，對上面的gRPC服務進行健康檢查：

grpc-health-probe -addr=localhost:50051           

如果是健康的服務，會有如下輸出：

status: SERVING           

如果服務挂掉了，會有如下輸出

timeout: failed to connect service "localhost:50051" within 1s           

或者

failed to connect service at "localhost:50051": context deadline exceeded
exit status 2