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// Copyright 2016 The LUCI Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package prpc
// This file implements encoding of RPC results to HTTP responses.
import (
"bytes"
"context"
"encoding/base64"
"fmt"
"io"
"net/http"
"sort"
"strconv"
"github.com/golang/protobuf/jsonpb"
"github.com/golang/protobuf/proto"
anypb "github.com/golang/protobuf/ptypes/any"
"google.golang.org/grpc/codes"
"google.golang.org/grpc/status"
"go.chromium.org/luci/common/errors"
"go.chromium.org/luci/common/logging"
"go.chromium.org/luci/grpc/grpcutil"
)
const (
headerAccept = "Accept"
)
// responseFormat returns the format to be used in a response.
// Can return only FormatBinary (preferred), FormatJSONPB or FormatText.
// In case of an error, format is undefined.
func responseFormat(acceptHeader string) (Format, *protocolError) {
if acceptHeader == "" {
return FormatBinary, nil
}
parsed, err := parseAccept(acceptHeader)
if err != nil {
return FormatBinary, errorf(http.StatusBadRequest, "Accept header: %s", err)
}
formats := make(acceptFormatSlice, 0, len(parsed))
for _, at := range parsed {
f, err := FormatFromMediaType(at.MediaType, at.MediaTypeParams)
if err != nil {
// Ignore invalid format. Check further.
continue
}
formats = append(formats, acceptFormat{f, at.QualityFactor})
}
if len(formats) == 0 {
return FormatBinary, errorf(
http.StatusNotAcceptable,
"Accept header: specified media types are not not supported. Supported types: %q, %q, %q, %q.",
FormatBinary.MediaType(),
FormatJSONPB.MediaType(),
FormatText.MediaType(),
ContentTypeJSON,
)
}
sort.Sort(formats) // order by quality factor and format preference.
return formats[0].Format, nil
}
// marshalMessage marshals msg in the given format.
//
// If wrap is true and format is JSON, then prepends JSONPBPrefix and appends
// \n.
func marshalMessage(msg proto.Message, format Format, wrap bool) ([]byte, error) {
if msg == nil {
panic("msg is nil")
}
var buf bytes.Buffer
switch format {
case FormatBinary:
return proto.Marshal(msg)
case FormatJSONPB:
if wrap {
buf.WriteString(JSONPBPrefix)
}
m := jsonpb.Marshaler{}
if err := m.Marshal(&buf, msg); err != nil {
return nil, err
}
if wrap {
buf.WriteRune('\n')
}
return buf.Bytes(), nil
case FormatText:
if err := proto.MarshalText(&buf, msg); err != nil {
return nil, err
}
return buf.Bytes(), nil
default:
panic(fmt.Errorf("impossible: invalid format %d", format))
}
}
// writeMessage writes msg to w in the specified format.
// c is used to log errors.
// panics if msg is nil.
func writeMessage(c context.Context, w http.ResponseWriter, msg proto.Message, format Format) {
if msg == nil {
panic("msg is nil")
}
body, err := marshalMessage(msg, format, true)
if err != nil {
writeError(c, w, withCode(err, codes.Internal), format)
return
}
w.Header().Set(HeaderGRPCCode, strconv.Itoa(int(codes.OK)))
w.Header().Set(headerContentType, format.MediaType())
if _, err := w.Write(body); err != nil {
logging.WithError(err).Errorf(c, "prpc: failed to write response body")
}
}
func errorStatus(err error) (st *status.Status, httpStatus int) {
if err == nil {
panic("err is nil")
}
if perr, ok := err.(*protocolError); ok {
st = status.New(codes.InvalidArgument, perr.err.Error())
httpStatus = perr.status
return
}
err = errors.Unwrap(err)
st, ok := status.FromError(err)
switch {
case ok:
// great.
case err == context.Canceled:
st = status.New(codes.Canceled, "canceled")
case err == context.DeadlineExceeded:
st = status.New(codes.DeadlineExceeded, "deadline exceeded")
default:
// st is non-nil because err is non-nil.
}
httpStatus = grpcutil.CodeStatus(st.Code())
return
}
func statusDetailsToHeaderValues(details []*anypb.Any, format Format) ([]string, error) {
ret := make([]string, len(details))
for i, det := range details {
msgBytes, err := marshalMessage(det, format, false)
if err != nil {
return nil, err
}
ret[i] = base64.StdEncoding.EncodeToString(msgBytes)
}
return ret, nil
}
// writeError writes err to w and logs it.
func writeError(c context.Context, w http.ResponseWriter, err error, format Format) {
st, httpStatus := errorStatus(err)
// use st.Proto instead of st.Details to avoid unnecessary unmarshaling of
// google.protobuf.Any underlying messages. We need Any protos themselves.
detailHeader, err := statusDetailsToHeaderValues(st.Proto().Details, format)
if err != nil {
st = status.New(codes.Internal, "prpc: failed to write status details")
httpStatus = http.StatusInternalServerError
} else {
w.Header()[HeaderStatusDetail] = detailHeader
}
body := st.Message()
if httpStatus < 500 {
logging.Warningf(c, "prpc: responding with %s error: %s", st.Code(), st.Message())
} else {
// Hide potential implementation details from the user.
body = http.StatusText(httpStatus)
// Log everything about the error.
logging.Errorf(c, "prpc: responding with %s error: %s", st.Code(), st.Message())
errors.Log(c, err)
}
w.Header().Set(HeaderGRPCCode, strconv.Itoa(int(st.Code())))
w.Header().Set(headerContentType, "text/plain")
w.WriteHeader(httpStatus)
if _, err := io.WriteString(w, body); err != nil {
logging.WithError(err).Errorf(c, "prpc: failed to write response body")
// The header is already written. There is nothing more we can do.
return
}
io.WriteString(w, "\n")
}
func withCode(err error, c codes.Code) error {
return status.Error(c, err.Error())
}