Provide multiple implementations of RPC responses on the fetch path.

This CL includes wrapper classes for the protocol buffer messages
`tensorflow::RunStepResponse` and `tensorflow::RunGraphResponse` (to
complement the corresponding request message wrappers that were added recently).

This change makes the backend code deal with abstract
`tensorflow::MutableRunStepResponseWrapper` and
`tensorflow::MutableRunGraphResponseWrapper` interfaces and adds three
concrete implementations of each interface:

* A mutable in-memory wrapper, which maintains the tensor data in
  `tensorflow::Tensor` objects, and provides the most efficient
  implementation when the client and master (or master and worker) or
  in the same address space.

* A mutable, owned protobuf wrapper, which has a similar implementation
  to today's client code.

* A mutable, non-owned protobuf wrapper, which has a similar
  implementation to today's server code (where the protobuf message is
  owned by the RPC subsystem).

This is another improvement for issue #6256.
Change: 144481118

1 files changed, 3 insertions, 3 deletions

diff --git a/tensorflow/core/distributed_runtime/master_session.h b/tensorflow/core/distributed_runtime/master_session.h
index 8ab46539f3..4e78e08559 100644
--- a/tensorflow/core/distributed_runtime/master_session.h
+++ b/tensorflow/core/distributed_runtime/master_session.h
@@ -80,7 +80,7 @@ class MasterSession : public core::RefCounted {
 
   // Run one step.
   Status Run(CallOptions* opts, const RunStepRequestWrapper& req,
-             RunStepResponse* resp);
+             MutableRunStepResponseWrapper* resp);
 
   // Close this session and delete "*this". Returns OK if all known
   // states are cleanup successfully.
@@ -177,9 +177,9 @@ class MasterSession : public core::RefCounted {
                       RCGMap* rcg_map) EXCLUSIVE_LOCKS_REQUIRED(mu_);
   Status DoRunWithLocalExecution(CallOptions* opts,
                                  const RunStepRequestWrapper& req,
-                                 RunStepResponse* resp);
+                                 MutableRunStepResponseWrapper* resp);
   Status DoPartialRun(CallOptions* opts, const RunStepRequestWrapper& req,
-                      RunStepResponse* resp);
+                      MutableRunStepResponseWrapper* resp);
   void UpdateLastAccessTime();
 
   Status BuildAndRegisterPartitions(ReffedClientGraph* rcg);