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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
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License.
package prpc
import (
// Options controls how RPC requests are sent.
type Options struct {
// Retry controls a strategy for retrying transient RPC errors and deadlines.
// Each call to this factory should return a new retry.Iterator to use for
// controlling retry loop of a single RPC call.
Retry retry.Factory
// UserAgent is the value of User-Agent HTTP header.
// If empty, DefaultUserAgent is used.
UserAgent string
// Insecure can be set to true to use HTTP instead of HTTPS.
// Useful for local tests.
Insecure bool
// PerRPCTimeout, if > 0, is a timeout that is applied to each call attempt.
// If the context passed to the call has a shorter deadline, this timeout will
// not be applied. Otherwise, if this timeout is hit, the RPC call attempt
// will be considered as failed transiently and it may be retried just like
// any other transient error per Retry policy.
PerRPCTimeout time.Duration
// AcceptContentSubtype defines acceptable Content-Type of responses.
// Valid values are "binary" and "json". Empty value defaults to "binary".
// It can be overridden on per-call basis via CallAcceptContentSubtype().
AcceptContentSubtype string
// Debug is a flag indicate if we want to print more logs for debug purpose.
// Right now we use this option to print the raw requests when certain
// failures occur.
Debug bool
// These can be set only using *prpc.CallOption or some grpc.CallOption.
resHeaderMetadata *metadata.MD // destination for response HTTP headers.
resTrailerMetadata *metadata.MD // destination for response HTTP trailers.
expectedCodes []codes.Code // list of non-OK grpc codes NOT to log
// These are used internally.
host string // a hostname of a service being called
serviceName string // a service being called
methodName string // a method being called
inFormat Format // encoding of the request
outFormat Format // encoding of the response
// DefaultOptions are used if no options are specified in Client.
func DefaultOptions() *Options {
return &Options{
Retry: func() retry.Iterator {
return &retry.ExponentialBackoff{
Limited: retry.Limited{
Delay: time.Second,
Retries: 5,
func (o *Options) apply(callOptions []grpc.CallOption) {
for _, co := range callOptions {
switch val := co.(type) {
case grpc.HeaderCallOption:
o.resHeaderMetadata = val.HeaderAddr
case grpc.TrailerCallOption:
o.resTrailerMetadata = val.TrailerAddr
case *CallOption:
panic(fmt.Sprintf("unsupported call option %T is used with pRPC client", co))
func (o *Options) resetResponseMetadata() {
if o.resHeaderMetadata != nil {
*o.resHeaderMetadata = nil
if o.resTrailerMetadata != nil {
*o.resTrailerMetadata = nil
// CallOption mutates Options.
type CallOption struct {
// apply mutates options.
apply func(*Options)
// ExpectedCode can be used to indicate that given non-OK codes may appear
// during normal successful call flow, and thus they must not be logged as
// erroneous.
// Only affects local logging, nothing else.
func ExpectedCode(codes *CallOption {
return &CallOption{
func(o *Options) {
o.expectedCodes = append(o.expectedCodes, codes...)
// CallAcceptContentSubtype returns a CallOption that sets Content-Type.
// For example, if content-subtype is "json", the Content-Type over the wire
// will be "application/json".
// Unlike that of the grpc.CallContentSubtype, sets Content-Type only for
// response, not for the request.
func CallAcceptContentSubtype(contentSubtype string) *CallOption {
return &CallOption{
func(o *Options) {
o.AcceptContentSubtype = strings.ToLower(contentSubtype)