common/prpc, tools/cmd/cproto: prpc client

server/prpc/encoding.go

Index: server/prpc/encoding.go
diff --git a/server/prpc/encoding.go b/server/prpc/encoding.go
index 2788e2e29d1d8b4a2a4b50380368de5e54399482..f02423850fb467447713a5bc75275074a6c63360 100644
--- a/server/prpc/encoding.go
+++ b/server/prpc/encoding.go
@@ -11,6 +11,7 @@ import (
 	"io"
 	"net/http"
 	"sort"
+	"strconv"
 
 	"github.com/golang/protobuf/jsonpb"
 	"github.com/golang/protobuf/proto"
@@ -18,11 +19,14 @@ import (
 	"google.golang.org/grpc"
 	"google.golang.org/grpc/codes"
 
+	"github.com/luci/luci-go/common/errors"
 	"github.com/luci/luci-go/common/logging"
+	"github.com/luci/luci-go/common/prpc"
 )
 
 const (
-	headerAccept = "Accept"
+	headerAccept   = "Accept"
+	headerGRPCCode = "X-Prpc-Grpc-Code"

[dnj, 2016/01/21 07:44:28]

Make this exported and reuse it in client? No point in repeating it.

[nodir, 2016/01/22 00:47:24]

Done, but vice-versa: common cannot import server

 )
 
 // responseFormat returns the format to be used in a response.
@@ -114,30 +118,6 @@ func writeMessage(w http.ResponseWriter, msg proto.Message, format format) error
 	return err
 }
 
-// codeToStatus maps gRPC codes to HTTP statuses.
-// This map may need to be corrected when
-// https://github.com/grpc/grpc-common/issues/210
-// is closed.
-var codeToStatus = map[codes.Code]int{
-	codes.OK:                 http.StatusOK,
-	codes.Canceled:           http.StatusNoContent,
-	codes.Unknown:            http.StatusInternalServerError,
-	codes.InvalidArgument:    http.StatusBadRequest,
-	codes.DeadlineExceeded:   http.StatusServiceUnavailable,
-	codes.NotFound:           http.StatusNotFound,
-	codes.AlreadyExists:      http.StatusConflict,
-	codes.PermissionDenied:   http.StatusForbidden,
-	codes.Unauthenticated:    http.StatusUnauthorized,
-	codes.ResourceExhausted:  http.StatusServiceUnavailable,
-	codes.FailedPrecondition: http.StatusPreconditionFailed,
-	codes.Aborted:            http.StatusInternalServerError,
-	codes.OutOfRange:         http.StatusBadRequest,
-	codes.Unimplemented:      http.StatusNotImplemented,
-	codes.Internal:           http.StatusInternalServerError,
-	codes.Unavailable:        http.StatusServiceUnavailable,
-	codes.DataLoss:           http.StatusInternalServerError,
-}
-
 // ErrorStatus returns HTTP status for an error.
 // In particular, it maps gRPC codes to HTTP statuses.
 // Status of nil is 200.
@@ -148,7 +128,7 @@ func ErrorStatus(err error) int {
 		return err.status
 	}
 
-	status, ok := codeToStatus[grpc.Code(err)]
+	status, ok := prpc.CodeStatus(grpc.Code(err))
 	if !ok {
 		status = http.StatusInternalServerError
 	}
@@ -186,6 +166,7 @@ func writeError(c context.Context, w http.ResponseWriter, err error) {
 		logging.Errorf(c, "HTTP %d: %s", status, ErrorDesc(err))
 	}
 
+	w.Header().Set(headerGRPCCode, strconv.Itoa(int(grpcCode(err))))
 	w.Header().Set(headerContentType, "text/plain")
 	w.WriteHeader(status)
 
@@ -200,6 +181,30 @@ func writeError(c context.Context, w http.ResponseWriter, err error) {
 	}
 }
 
+// returns the most appropriate gRPC code for an error.
+func grpcCode(err error) codes.Code {
+	if err == nil {
+		return codes.OK
+	}
+
+	for ; err != nil; err = errors.Unwrap(err) {
+		if code := grpc.Code(err); code != codes.Unknown {
+			return code
+		}
+
+		switch err {
+
+		case context.Canceled:
+			return codes.Canceled
+
+		case context.DeadlineExceeded:
+			return codes.DeadlineExceeded
+
+		}
+	}
+	return codes.Unknown
+}
+
 func assert(condition bool) {
 	if !condition {
 		panicf("assertion failed")