Go の gRPC で Redis のデータを更新 (Update)

設定ファイル、サーバープログラム、クライアントプログラムの３つが必要です。

```text
$ tree
.
├── redis_update
│   └── redis_update.proto
├── redis_update_client
│   └── main.go
└── redis_update_server
    └── main.go
```

設定ファイル
>redis_update/redis_update.proto
こちらと同じ
[Python の gRPC で Redis のデータを更新 (Update)](https://qiita.com/ekzemplaro/items/1e94293e0471504b0663)

サーバープログラム

```go:redis_update_server/main.go
// ---------------------------------------------------------------
//
//	redis_update_server/main.go
//
//					Feb/11/2020	
// ---------------------------------------------------------------
package main

import (
	"context"
	"log"
	"net"
	"fmt"
	"os"
	"encoding/json"
	"time"
	"strconv"
	"strings"

	"google.golang.org/grpc"
	pb "../redis_update"
)

const (
	port = ":50051"
)

type server struct {
	pb.UnimplementedGreeterServer
}

// ---------------------------------------------------------------
func get_current_date_proc () string {
	now := time.Now ()
	fmt.Printf ("%s\t" ,now)
	fmt.Printf ("%d-%d-%d\n" ,now.Year (),now.Month(),now.Day())
	today := strconv.Itoa (now.Year()) + "-" +
		fmt.Sprintf ("%d",now.Month()) + "-" +
		strconv.Itoa (now.Day())

	return	today
}

// ---------------------------------------------------------------
func json_update_proc (json_str string,population_in int) string {

	var unit_aa map[string]interface{}
	json.Unmarshal ([]byte(json_str), &unit_aa)
	fmt.Printf ("%s\t",unit_aa["name"])
	fmt.Printf ("%f\t",unit_aa["population"])
	fmt.Printf ("%s\n",unit_aa["date_mod"])

	unit_aa["population"] = population_in
	unit_aa["date_mod"] = get_current_date_proc ()

	output, _ := json.Marshal(unit_aa)

	json_str = string(output)

	return	json_str
}

// ---------------------------------------------------------------
func redis_socket_write_proc (conn net.Conn,key_in string,json_str string) {
	fmt.Println (key_in)
	fmt.Println (json_str)

	comm_aa := "set " + key_in + " '" + json_str + "'\r\n"
	conn.Write([]byte(comm_aa))


	buf := make ([]byte,1024)
	conn.Read (buf[:])

	fmt.Println (string(buf[0:10]))
}

// ---------------------------------------------------------------
func socket_read_proc (conn net.Conn,key_in string) string {
	str_received := ""
	_, err := conn.Write([]byte("get " + key_in + "\r\n"))
	if err != nil {
		fmt.Println(err)
		return str_received
		}

	buf := make([]byte, 1024)
	nn, err := conn.Read(buf[:])
	if err != nil {
		fmt.Println(err)
		return str_received
		}

	str_received = string(buf[0:nn])

	return	str_received
}

// ---------------------------------------------------------------
func redis_socket_read_proc (conn net.Conn,key_in string) string {
	json_str := ""
	str_received := socket_read_proc (conn,key_in)

	lines := strings.Split(str_received,"\n")

	if (! strings.Contains(lines[0],"END")) {
		json_str = lines[1]
		}

	return	json_str
}

// ---------------------------------------------------------------
func redis_update_proc (key_in string,population int32) string {
	str_json := ""

	hostname := "localhost"
	port := "6379"

	conn, err := net.Dial ("tcp", hostname + ":" + port)
	if err != nil {
		fmt.Println(err)
		return str_json
		}

	str_json = redis_socket_read_proc (conn,key_in)

	fmt.Fprintf (os.Stderr,"str_json = " + str_json + "\n")
	str_json_new := json_update_proc (str_json,int(population))
	fmt.Println (str_json_new)
	redis_socket_write_proc (conn,key_in,str_json_new)

	return key_in
}
// ---------------------------------------------------------------
func (s *server) RedisUpdate(ctx context.Context, in *pb.RedisRequest) (*pb.RedisReply, error) {
//	log.Printf("SayHello Received: %v", in.GetName())
	fmt.Fprintf (os.Stderr,"*** check aaa ***\n")
	key := in.GetKey()
	population := in.GetPopulation()
	fmt.Fprintf (os.Stderr,"key = " + key + "\n")
	fmt.Fprintf (os.Stderr,"population = %d\n" , population)
	rkey := redis_update_proc (key,population)
	return &pb.RedisReply{Key: rkey }, nil
}

// ---------------------------------------------------------------
func main() {
	lis, err := net.Listen("tcp", port)
	if err != nil {
		log.Fatalf("failed to listen: %v", err)
	}
	s := grpc.NewServer()
	pb.RegisterGreeterServer(s, &server{})
	if err := s.Serve(lis); err != nil {
		log.Fatalf("failed to serve: %v", err)
	}
}

// ---------------------------------------------------------------
```

クライアントプログラム

```go:redis_update_client/main.go
// ---------------------------------------------------------------
//
//	redis_update_client/main.go
//
//					Feb/11/2020
//
// ---------------------------------------------------------------
package main

import (
	"context"
	"fmt"
	"log"
	"os"
	"strconv"
	"time"

	"google.golang.org/grpc"
	pb "../redis_update"
)

const (
	address     = "localhost:50051"
	defaultKey = "t0001"
	defaultPopulation = int32(12345)
)

// ---------------------------------------------------------------
func main() {
	// Set up a connection to the server.
	conn, err := grpc.Dial(address, grpc.WithInsecure(), grpc.WithBlock())
	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.
	key := defaultKey
	population := defaultPopulation
	if len(os.Args) > 1 {
		key = os.Args[1]
		ppt,_ := strconv.Atoi (os.Args[2])
		population = int32(ppt)
	}
	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
	defer cancel()
	r, err := c.RedisUpdate(ctx, &pb.RedisRequest{Key: key,Population: population})
	if err != nil {
		log.Fatalf("could not greet: %v", err)
	}

	rvalue := r.GetKey()

	fmt.Printf ("%s\n",rvalue)
}

// ---------------------------------------------------------------
```

gRPC のコードを作成します。

スクリプト

```bash
protoc -I redis_update redis_update/redis_update.proto --go_out=plugins=grpc:redis_update
```


サーバープログラムの起動

```bash
go run redis_update_server/main.go
```

クライアントプログラムの実行

```text
$ go run redis_update_client/main.go t1858 3298700
t1858
```