Go : grpc下载文件+Status+Code


简介

在使用grpc的过程中， 有错误的情况下不管是服务器端还是客户端， 直接返回错误之后在另外一端出现了 rpc error: code = Unknown desc = xxxxxx, 所以, 不好进行判断， 下面就使用grpc包内的status 和 codes包, 使返回值方便解析和更好复用grpc错误, 顺道将一些技巧顺带使用

代码

download.proto

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syntax = "proto3";

//package download;

//option csharp_namespace = "Google.Protobuf.WellKnownTypes";
option go_package = "../proto";
//option java_package = "com.google.protobuf";
//option java_outer_classname = "AnyProto";
//option java_multiple_files = true;
option objc_class_prefix = "GPB";

service DownloadService{
    rpc Download(DownloadRequest) returns (stream DownloadResponse) {};
}

message DownloadRequest {
    string FilePath = 1;
    int32  MaxSize = 2; // 每一次下载的最大大小 单位MB
}

message DownloadResponse {
    string Name = 1;
    bytes  Buffer = 2;
    bool   IsDir = 3;

}

指令生成 download.pb.go

protoc -I ./ --go_out=plugins=grpc:. ./download.proto

server.go

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package main

import (
    pb "download/proto"
    "google.golang.org/grpc/codes"
    "google.golang.org/grpc/status"
)

var gDownloader = &Downloader{}

type DownloadServer struct {

}

func (d *DownloadServer) Download(in *pb.DownloadRequest, stream pb.DownloadService_DownloadServer) error {
    err := gDownloader.Download(in.FilePath, func (buffer []byte) error{
        return stream.Send(&pb.DownloadResponse{
            Buffer: buffer,
        })
    })

    if EndOfError == err {
        return status.Error(codes.Code(EOF), CodeToStr(EOF))
    }

    if NormallyCloseError == err {
        return status.Error(codes.Code(NORMALLY_EXIST), CodeToStr(NORMALLY_EXIST))
    }

    return err
}

client.go

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package main

import (
    "context"
    pb "download/proto"
    "fmt"
    "google.golang.org/grpc"
    "google.golang.org/grpc/status"
    "log"
)

func download(client pb.DownloadServiceClient, r *pb.DownloadRequest) error {
    stream, err := client.Download(context.Background(), r)
    if err != nil {
        return err
    }
    for {
        resp, err := stream.Recv()
        status := status.Convert(err)

        if status.Code() == EOF {
            fmt.Println("文件正常结束...")
            break
        }
        if err != nil {
            return err
        }
        fmt.Println("返回值:", resp)
    }

    return nil
}

func Download(host string) error {
    var (
        conn       *grpc.ClientConn
        err        error
        grpcClient pb.DownloadServiceClient
    )
    conn, err = grpc.Dial(host, grpc.WithInsecure())
    if err != nil {
        log.Fatalf("grpc.Dial err: %v", err)
        return err
    }
    defer conn.Close()

    grpcClient = pb.NewDownloadServiceClient(conn)

    return download(grpcClient, &pb.DownloadRequest{FilePath: string("D:\\Softwares\\360\\360Safe\\360Base.dll")})
}

service.go

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package main

import (
    pb "download/proto"
    "google.golang.org/grpc"
    "log"
    "net"
)

func RunDownloadService(network, host string) error {
    server := grpc.NewServer()
    pb.RegisterDownloadServiceServer(server, &DownloadServer{})

    lis, err := net.Listen(network, host)
    if err != nil {
        log.Fatalf("net.Listen err: %v", err)
        return err
    }

    err = server.Serve(lis)
    if err != nil {
        log.Fatalf("net.Listen err: %v", err)
    }
    return err
}

codes.go

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package main

import "io"

const (
    EOF = 1024 + iota
    NORMALLY_EXIST
)

var codeToStr = map[int] string {
    EOF: io.EOF.Error(),
    NORMALLY_EXIST: "normally close",
}

func CodeToStr(code int) string {
    v, _ := codeToStr[code]
    return v
}

downloader.go

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package main

import (
    "errors"
    "io"
    "os"
    "sync"
)

var NormallyCloseError = errors.New(CodeToStr(NORMALLY_EXIST))
var EndOfError = errors.New(CodeToStr(EOF))

type Downloader struct {
    waiter sync.WaitGroup
    mu sync.Mutex

    exitChans []chan int
}

func (d *Downloader) WaitForDone() {
    d.waiter.Wait()
}

func (d *Downloader) CacelAllAndWaitForDone() {
    d.mu.Lock()
    defer d.mu.Unlock()

    d.SendToExitChans()

    d.waiter.Wait()

    d.freeAllExitChan()
}

func (d *Downloader) NewExitChan() chan int {
    d.mu.Lock()
    defer d.mu.Unlock()

    return d.newExitChan()
}

func (d *Downloader) FreeExitChan(c chan int) {
    d.mu.Lock()
    defer d.mu.Unlock()

    d.freeExitChan(c)
}

func (d *Downloader) FreeAllExitChan() {
    d.mu.Lock()
    defer d.mu.Unlock()

    d.freeAllExitChan()
}

func (d *Downloader) SendToExitChans() {
    d.mu.Lock()
    defer d.mu.Unlock()

    for i, _ := range d.exitChans {
        go func() {
            d.exitChans[i] <- 1
        } ()
    }
}

func (d *Downloader) newExitChan() chan int {
    if nil == d.exitChans { d.exitChans = make([]chan int, 0) }

    var chn = make(chan int, 1)

    d.exitChans = append(d.exitChans, chn)

    return chn
}

func (d *Downloader) freeExitChan(c chan int) {
    for i, chn := range d.exitChans {
        if chn == c {
            d.exitChans[i] = nil
            d.exitChans = append(d.exitChans[:i], d.exitChans[i+1:]...)
            break
        }
    }
}

func (d *Downloader) freeAllExitChan() {
    for i, _ := range d.exitChans {
        d.exitChans[i] = nil
    }
    d.exitChans = nil
}

func (d *Downloader) Download(dst string, f func (buffer []byte) error) error {
    d.waiter.Add(1)
    defer d.waiter.Done()

    exitChan := d.NewExitChan()
    defer func() {
        d.FreeExitChan(exitChan)
    } ()

    var file, err = os.Open(dst)
    if nil != err { return err }
    defer file.Close()
    var maxSize = 1024
    var buffer = make([]byte, maxSize)
    var n int

    for {
        select {
        case <-exitChan:
            return NormallyCloseError
        default:
            n, err = file.Read(buffer)
            if nil != err {
                if io.EOF != err {
                    return err
                }
            }
            if 0 < n {
                err = f(buffer[:n])
                if nil != err { return nil }
            }
        }
        if n < maxSize { return EndOfError }
    }
}

资源

代码 - https://download.csdn.net/download/halo_hsuh/12547363