Add WriteStateToFileResponse. (#1428)

Changes the public map builder API, but is required to not break the ROS API.
See also https://github.com/googlecartographer/cartographer_ros/pull/1014 and #1422

cartographer/cloud/client/map_builder_stub.cc

@@ -153,7 +153,7 @@ void MapBuilderStub::SerializeState(bool include_unfinished_submaps,
   }
 }
 
-void MapBuilderStub::SerializeStateToFile(bool include_unfinished_submaps,
+bool MapBuilderStub::SerializeStateToFile(bool include_unfinished_submaps,
                                           const std::string& filename) {
   if (include_unfinished_submaps) {
     LOG(WARNING) << "Serializing unfinished submaps is currently unsupported. "
@@ -164,10 +164,13 @@ void MapBuilderStub::SerializeStateToFile(bool include_unfinished_submaps,
   ::grpc::Status status;
   async_grpc::Client<handlers::WriteStateToFileSignature> client(
       client_channel_);
-  CHECK(client.Write(request, &status))
+  if (!client.Write(request, &status)) {
+    LOG(ERROR) << "WriteStateToFileRequest failed - "
                << "code: " << status.error_code()
                << " reason: " << status.error_message();
   }
+  return client.response().success();
+}
 
 std::map<int, int> MapBuilderStub::LoadState(
     io::ProtoStreamReaderInterface* reader, const bool load_frozen_state) {

cartographer/cloud/client/map_builder_stub.h

@@ -50,7 +50,7 @@ class MapBuilderStub : public mapping::MapBuilderInterface {
       mapping::proto::SubmapQuery::Response* response) override;
   void SerializeState(bool include_unfinished_submaps,
                       io::ProtoStreamWriterInterface* writer) override;
-  void SerializeStateToFile(bool include_unfinished_submaps,
+  bool SerializeStateToFile(bool include_unfinished_submaps,
                             const std::string& filename) override;
   std::map<int, int> LoadState(io::ProtoStreamReaderInterface* reader,
                                bool load_frozen_state) override;

cartographer/cloud/internal/handlers/write_state_to_file_handler.cc

@@ -16,6 +16,7 @@
 
 #include "cartographer/cloud/internal/handlers/write_state_to_file_handler.h"
 
+#include "absl/memory/memory.h"
 #include "async_grpc/rpc_handler.h"
 #include "cartographer/cloud/internal/map_builder_context_interface.h"
 #include "cartographer/cloud/internal/map_builder_server.h"
@@ -32,8 +33,14 @@ void WriteStateToFileHandler::OnRequest(
     Finish(::grpc::Status(::grpc::INVALID_ARGUMENT, "Filename empty."));
     return;
   }
-  GetContext<MapBuilderContextInterface>()->map_builder().SerializeStateToFile(
+  bool success =
+      GetContext<MapBuilderContextInterface>()
+          ->map_builder()
+          .SerializeStateToFile(
               /*include_unfinished_submaps=*/false, request.filename());
+  auto response = absl::make_unique<proto::WriteStateToFileResponse>();
+  response->set_success(success);
+  Send(std::move(response));
 }
 
 }  // namespace handlers

cartographer/cloud/internal/handlers/write_state_to_file_handler.h

@@ -27,7 +27,7 @@ namespace handlers {
 
 DEFINE_HANDLER_SIGNATURE(
     WriteStateToFileSignature, proto::WriteStateToFileRequest,
-    google::protobuf::Empty,
+    proto::WriteStateToFileResponse,
     "/cartographer.cloud.proto.MapBuilderService/WriteStateToFile")
 
 class WriteStateToFileHandler

cartographer/cloud/proto/map_builder_service.proto

@@ -232,6 +232,10 @@ message WriteStateToFileRequest {
   string filename = 1;
 }
 
+message WriteStateToFileResponse {
+  bool success = 1;
+}
+
 message IsTrajectoryFinishedRequest {
   int32 trajectory_id = 1;
 }
@@ -345,5 +349,6 @@ service MapBuilderService {
   rpc WriteState(google.protobuf.Empty) returns (stream WriteStateResponse);
 
   // Writes the serialized SLAM state to the host file system.
-  rpc WriteStateToFile(WriteStateToFileRequest) returns (google.protobuf.Empty);
+  rpc WriteStateToFile(WriteStateToFileRequest)
+      returns (WriteStateToFileResponse);
 }

cartographer/mapping/internal/testing/mock_map_builder.h

@@ -48,7 +48,7 @@ class MockMapBuilder : public mapping::MapBuilderInterface {
                std::string(const mapping::SubmapId &,
                            mapping::proto::SubmapQuery::Response *));
   MOCK_METHOD2(SerializeState, void(bool, io::ProtoStreamWriterInterface *));
-  MOCK_METHOD2(SerializeStateToFile, void(bool, const std::string &));
+  MOCK_METHOD2(SerializeStateToFile, bool(bool, const std::string &));
   MOCK_METHOD2(LoadState,
                std::map<int, int>(io::ProtoStreamReaderInterface *, bool));
   MOCK_METHOD2(LoadStateFromFile,

cartographer/mapping/map_builder.cc

@@ -212,12 +212,12 @@ void MapBuilder::SerializeState(bool include_unfinished_submaps,
                     include_unfinished_submaps);
 }
 
-void MapBuilder::SerializeStateToFile(bool include_unfinished_submaps,
+bool MapBuilder::SerializeStateToFile(bool include_unfinished_submaps,
                                       const std::string& filename) {
   io::ProtoStreamWriter writer(filename);
   io::WritePbStream(*pose_graph_, all_trajectory_builder_options_, &writer,
                     include_unfinished_submaps);
-  writer.Close();
+  return (writer.Close());
 }
 
 std::map<int, int> MapBuilder::LoadState(

cartographer/mapping/map_builder.h

@@ -59,7 +59,7 @@ class MapBuilder : public MapBuilderInterface {
   void SerializeState(bool include_unfinished_submaps,
                       io::ProtoStreamWriterInterface *writer) override;
 
-  void SerializeStateToFile(bool include_unfinished_submaps,
+  bool SerializeStateToFile(bool include_unfinished_submaps,
                             const std::string &filename) override;
 
   std::map<int, int> LoadState(io::ProtoStreamReaderInterface *reader,

cartographer/mapping/map_builder_interface.h

@@ -88,7 +88,8 @@ class MapBuilderInterface {
   // 'include_unfinished_submaps' is set to true, unfinished submaps, i.e.
   // submaps that have not yet received all rangefinder data insertions, will
   // be included in the serialized state.
-  virtual void SerializeStateToFile(bool include_unfinished_submaps,
+  // Returns true if the file was successfully written.
+  virtual bool SerializeStateToFile(bool include_unfinished_submaps,
                                     const std::string& filename) = 0;
 
   // Loads the SLAM state from a proto stream. Returns the remapping of new