C++ API for write-through

include/grpc++/impl/codegen/call.h

@@ -169,6 +169,15 @@ class WriteOptions {
     return *this;
   }
 
+  /// Guarantee that all bytes have been written to the wire before completing
+  /// this write (usually writes are completed when they pass flow control)
+  inline WriteOptions& set_write_through() {
+    SetBit(GRPC_WRITE_THROUGH);
+    return *this;
+  }
+
+  inline bool is_write_through() const { return GetBit(GRPC_WRITE_THROUGH); }
+
   /// Get value for the flag indicating that this is the last message, and
   /// should be coalesced with trailing metadata.
   ///

test/cpp/end2end/end2end_test.cc

@@ -731,6 +731,22 @@ TEST_P(End2endTest, RequestStreamTwoRequests) {
   EXPECT_TRUE(s.ok());
 }
 
+TEST_P(End2endTest, RequestStreamTwoRequestsWithWriteThrough) {
+  ResetStub();
+  EchoRequest request;
+  EchoResponse response;
+  ClientContext context;
+
+  auto stream = stub_->RequestStream(&context, &response);
+  request.set_message("hello");
+  EXPECT_TRUE(stream->Write(request, WriteOptions().set_write_through()));
+  EXPECT_TRUE(stream->Write(request, WriteOptions().set_write_through()));
+  stream->WritesDone();
+  Status s = stream->Finish();
+  EXPECT_EQ(response.message(), "hellohello");
+  EXPECT_TRUE(s.ok());
+}
+
 TEST_P(End2endTest, RequestStreamTwoRequestsWithCoalescingApi) {
   ResetStub();
   EchoRequest request;