gRPC错误处理

err := status.Error(codes.NotFound, "id was not found")
return nil, err

st, ok := status.FromError(err)
if !ok {
	//不含状态码的错误处理
}
//使用st.Message()，和st.Code()方法分别读取错误信息和错误码

st := status.New(code.NotFound, "id was not found")
d := &errdetails.LocalizedMessage{
	Locale: "en-US",
	Message: fmt.Sprintf("we couldn't find a user with the email address:  %s", id),
}
var err error
st, err = st.WithDetails(d)
if err != nil {
	panic(fmt.Sprintf("Unexpected error attaching metadata: %v", err))
}
return st.Err()

st := status.Convert(err)
for _, detail := range st.Details() {
    switch t := detail.(type) {
	case *errdetails.LocalizedMessage:
	//将t.Message发送给用户
    }
}

proglog/api/v1/error.go

package log_v1

import (
	"fmt"

	"google.golang.org/genproto/googleapis/rpc/errdetails"
	"google.golang.org/grpc/status"
)

type ErrOutOfRange struct {
	Offset uint64
}

func (e ErrOutOfRange) GRPCStatus() *status.Status {
    st := status.New(
        404,
        fmt.Sprintf("offset out of range: %d", e.Offset),
	)
    msg := fmt.Sprintf("the request offset is outside the log's range: %d", e.Offset)

    d := &errdetails.LocalizedMessage{
	    Locale:  "en-US",
	    Message: msg,
	}
	std, err := st.WithDetails(d)
	if err != nil {
	    return st
	}
    return std
}

func (e ErrOutOfRange) Error() string {
    return e.GRPCStatus().Err().Error()
}

if s == nil || s.nextOffset < off {
    return nil, fmt.Error("offset out of range: "%d", off)
}

将返回错误更新如下：

if s == nil || s.nextOffset < off {
    return nil, api.ErrOutOfRange{Offset: off}
}
return s.Read(off)

func testOutOfRangeErr(t *testing.T, log *Log) {
    read, err := log.Read(1)
    require.Nil(t, read)
    apiError := err.(api.ErrOutOfRange)
    require.Equal(t, uint64(1), apiError.Offset)
}

func (s *grpcServer) ConsumeStream(req *api.ConsumeRequest, stream api.Log_ConsumeStreamServer) error {
    for {
	select {
	case <-stream.Context().Done():
		return nil
	default:
		res, err := s.Consume(stream.Context(), req)
		switch err.(type) {
		case nil:
		case api.ErrOutOfRange:
			continue
		default:
			return err
		}
		if err = stream.Send(res); err != nil {
			return err
		}
		    eq.Offset++
	    }
    }
}