From 58ba322bb45d99659e3944bad05a389a49da5e5e Mon Sep 17 00:00:00 2001
From: Gyuho Lee <leegyuho@amazon.com>
Date: Mon, 9 Mar 2020 14:46:28 -0700
Subject: [PATCH] clientv3: embed API version

Signed-off-by: Gyuho Lee <leegyuho@amazon.com>
---
 clientv3/ctx.go                     | 13 +++++++++++++
 clientv3/ctx_test.go                | 20 ++++++++++++++++++--
 clientv3/retry_interceptor.go       |  2 ++
 etcdserver/api/v3rpc/rpctypes/md.go |  2 ++
 4 files changed, 35 insertions(+), 2 deletions(-)

diff --git a/clientv3/ctx.go b/clientv3/ctx.go
index c1e8be6fe..869b0fa69 100644
--- a/clientv3/ctx.go
+++ b/clientv3/ctx.go
@@ -18,6 +18,7 @@ import (
 	"context"
 
 	"go.etcd.io/etcd/etcdserver/api/v3rpc/rpctypes"
+	"go.etcd.io/etcd/version"
 	"google.golang.org/grpc/metadata"
 )
 
@@ -33,3 +34,15 @@ func WithRequireLeader(ctx context.Context) context.Context {
 	md.Set(rpctypes.MetadataRequireLeaderKey, rpctypes.MetadataHasLeader)
 	return metadata.NewOutgoingContext(ctx, md)
 }
+
+// embeds client version
+func withVersion(ctx context.Context) context.Context {
+	md, ok := metadata.FromOutgoingContext(ctx)
+	if !ok { // no outgoing metadata ctx key, create one
+		md = metadata.Pairs(rpctypes.MetadataClientAPIVersionKey, version.APIVersion)
+		return metadata.NewOutgoingContext(ctx, md)
+	}
+	// overwrite/add version key/value
+	md.Set(rpctypes.MetadataClientAPIVersionKey, version.APIVersion)
+	return metadata.NewOutgoingContext(ctx, md)
+}
diff --git a/clientv3/ctx_test.go b/clientv3/ctx_test.go
index d87728a98..89d966643 100644
--- a/clientv3/ctx_test.go
+++ b/clientv3/ctx_test.go
@@ -20,6 +20,7 @@ import (
 	"testing"
 
 	"go.etcd.io/etcd/etcdserver/api/v3rpc/rpctypes"
+	"go.etcd.io/etcd/version"
 	"google.golang.org/grpc/metadata"
 )
 
@@ -42,10 +43,25 @@ func TestMetadataWithRequireLeader(t *testing.T) {
 	if !ok {
 		t.Fatal("expected outgoing metadata ctx key")
 	}
-	if ss := md.Get("hasleader"); !reflect.DeepEqual(ss, []string{"true"}) {
-		t.Fatalf("unexpected metadata for 'hasleader' %v", ss)
+	if ss := md.Get(rpctypes.MetadataRequireLeaderKey); !reflect.DeepEqual(ss, []string{rpctypes.MetadataHasLeader}) {
+		t.Fatalf("unexpected metadata for %q %v", rpctypes.MetadataRequireLeaderKey, ss)
 	}
 	if ss := md.Get("hello"); !reflect.DeepEqual(ss, []string{"1", "2"}) {
 		t.Fatalf("unexpected metadata for 'hello' %v", ss)
 	}
 }
+
+func TestMetadataWithClientAPIVersion(t *testing.T) {
+	ctx := withVersion(WithRequireLeader(context.TODO()))
+
+	md, ok := metadata.FromOutgoingContext(ctx)
+	if !ok {
+		t.Fatal("expected outgoing metadata ctx key")
+	}
+	if ss := md.Get(rpctypes.MetadataRequireLeaderKey); !reflect.DeepEqual(ss, []string{rpctypes.MetadataHasLeader}) {
+		t.Fatalf("unexpected metadata for %q %v", rpctypes.MetadataRequireLeaderKey, ss)
+	}
+	if ss := md.Get(rpctypes.MetadataClientAPIVersionKey); !reflect.DeepEqual(ss, []string{version.APIVersion}) {
+		t.Fatalf("unexpected metadata for %q %v", rpctypes.MetadataClientAPIVersionKey, ss)
+	}
+}
diff --git a/clientv3/retry_interceptor.go b/clientv3/retry_interceptor.go
index aac679ecc..2c266e55b 100644
--- a/clientv3/retry_interceptor.go
+++ b/clientv3/retry_interceptor.go
@@ -38,6 +38,7 @@ import (
 func (c *Client) unaryClientInterceptor(logger *zap.Logger, optFuncs ...retryOption) grpc.UnaryClientInterceptor {
 	intOpts := reuseOrNewWithCallOptions(defaultOptions, optFuncs)
 	return func(ctx context.Context, method string, req, reply interface{}, cc *grpc.ClientConn, invoker grpc.UnaryInvoker, opts ...grpc.CallOption) error {
+		ctx = withVersion(ctx)
 		grpcOpts, retryOpts := filterCallOptions(opts)
 		callOpts := reuseOrNewWithCallOptions(intOpts, retryOpts)
 		// short circuit for simplicity, and avoiding allocations.
@@ -103,6 +104,7 @@ func (c *Client) unaryClientInterceptor(logger *zap.Logger, optFuncs ...retryOpt
 func (c *Client) streamClientInterceptor(logger *zap.Logger, optFuncs ...retryOption) grpc.StreamClientInterceptor {
 	intOpts := reuseOrNewWithCallOptions(defaultOptions, optFuncs)
 	return func(ctx context.Context, desc *grpc.StreamDesc, cc *grpc.ClientConn, method string, streamer grpc.Streamer, opts ...grpc.CallOption) (grpc.ClientStream, error) {
+		ctx = withVersion(ctx)
 		grpcOpts, retryOpts := filterCallOptions(opts)
 		callOpts := reuseOrNewWithCallOptions(intOpts, retryOpts)
 		// short circuit for simplicity, and avoiding allocations.
diff --git a/etcdserver/api/v3rpc/rpctypes/md.go b/etcdserver/api/v3rpc/rpctypes/md.go
index 5c590e1ae..90b8b835b 100644
--- a/etcdserver/api/v3rpc/rpctypes/md.go
+++ b/etcdserver/api/v3rpc/rpctypes/md.go
@@ -17,4 +17,6 @@ package rpctypes
 var (
 	MetadataRequireLeaderKey = "hasleader"
 	MetadataHasLeader        = "true"
+
+	MetadataClientAPIVersionKey = "client-api-version"
 )