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

common/prpc/options.go

Index: common/prpc/options.go
diff --git a/common/prpc/options.go b/common/prpc/options.go
new file mode 100644
index 0000000000000000000000000000000000000000..f9c9fc8032f4b1c291c193abf6cfd567e0f07545
--- /dev/null
+++ b/common/prpc/options.go
@@ -0,0 +1,83 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+package prpc
+
+import (
+	"fmt"
+	"time"
+
+	"google.golang.org/grpc"
+	"google.golang.org/grpc/metadata"
+
+	"github.com/luci/luci-go/common/retry"
+)
+
+// Options controls how RPC requests are sent.
+type Options struct {
+	Retry func() retry.Iterator // RPC retrial.
+
+	// UserAgent is the value of User-Agent HTTP header.
+	// If empty, DefaultUserAgent is used.
+	UserAgent string
+	Insecure  bool // if true, use HTTP instead of HTTPS.
+
+	// the rest can be set only using CallOption.
+
+	resHeaderMetadata  *metadata.MD // destination for response HTTP headers.
+	resTrailerMetadata *metadata.MD // destination for response HTTP trailers.
+}
+
+// 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 {
+		prpcCo, ok := co.(CallOption)
+		if !ok {
+			panic(fmt.Errorf("non-pRPC call option %T is used with pRPC client", co))
+		}
+		prpcCo.apply(o)
+	}
+}
+
+// CallOption mutates Options.
+type CallOption struct {
+	grpc.CallOption
+	// apply mutates options.
+	apply func(*Options)
+}
+
+// Header returns a CallOption that retrieves the header metadata.
+// Can be used instead of with grpc.Header.
+func Header(md *metadata.MD) *CallOption {
+	return &CallOption{
+		grpc.Header(md),
+		func(o *Options) {
+			o.resHeaderMetadata = md
+		},
+	}
+}
+
+// Trailer returns a CallOption that retrieves the trailer metadata.
+// Can be used instead of grpc.Trailer.
+func Trailer(md *metadata.MD) *CallOption {
+	return &CallOption{
+		grpc.Trailer(md),
+		func(o *Options) {
+			o.resTrailerMetadata = md
+		},
+	}
+}