Add binary for cartographer_grpc_server. (#747)

[RFC=0002](https://github.com/googlecartographer/rfcs/blob/master/text/0002-cloud-based-mapping-1.md)

CMakeLists.txt

@@ -154,6 +154,13 @@ google_binary(cartographer_compute_relations_metrics
     cartographer/ground_truth/compute_relations_metrics_main.cc
 )
 
+if(${BUILD_GRPC})
+  google_binary(cartographer_grpc_server
+    SRCS
+      cartographer_grpc/map_builder_server_main.cc
+  )
+endif()
+
 foreach(ABS_FIL ${ALL_TESTS})
   file(RELATIVE_PATH REL_FIL ${PROJECT_SOURCE_DIR} ${ABS_FIL})
   get_filename_component(DIR ${REL_FIL} DIRECTORY)
@@ -195,6 +202,9 @@ target_include_directories(${PROJECT_NAME} SYSTEM PUBLIC
 # TODO(hrapp): This should not explicitly list pthread and use
 # PROTOBUF_LIBRARIES, but that failed on first try.
 target_link_libraries(${PROJECT_NAME} PUBLIC ${PROTOBUF_LIBRARY} pthread)
+if(${BUILD_GRPC})
+  target_link_libraries(${PROJECT_NAME} PUBLIC grpc++)
+endif()
 
 # Add the binary directory first, so that port.h is included after it has
 # been generated.

cartographer_grpc/map_builder_server_main.cc

@@ -0,0 +1,58 @@
+/*
+ * Copyright 2017 The Cartographer Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "cartographer_grpc/map_builder_server.h"
+#include "cartographer_grpc/map_builder_server_options.h"
+#include "gflags/gflags.h"
+#include "glog/logging.h"
+
+DEFINE_string(configuration_directory, "",
+              "First directory in which configuration files are searched, "
+              "second is always the Cartographer installation to allow "
+              "including files from there.");
+DEFINE_string(configuration_basename, "",
+              "Basename, i.e. not containing any directory prefix, of the "
+              "configuration file.");
+
+namespace cartographer_grpc {
+
+void Run(const std::string& configuration_directory,
+         const std::string& configuration_basename) {
+  proto::MapBuilderServerOptions map_builder_server_options =
+      LoadMapBuilderServerOptions(configuration_directory,
+                                  configuration_basename);
+  MapBuilderServer map_builder_server(map_builder_server_options);
+  map_builder_server.Start();
+  map_builder_server.WaitForShutdown();
+}
+
+}  // namespace cartographer_grpc
+
+int main(int argc, char** argv) {
+  google::InitGoogleLogging(argv[0]);
+  FLAGS_logtostderr = true;
+  google::SetUsageMessage(
+      "\n\n"
+      "This program offers a MapBuilder service via a gRPC interface.\n");
+  google::ParseCommandLineFlags(&argc, &argv, true);
+  if (FLAGS_configuration_directory.empty() ||
+      FLAGS_configuration_basename.empty()) {
+    google::ShowUsageWithFlagsRestrict(argv[0], "cartographer_grpc_server");
+    return EXIT_FAILURE;
+  }
+  cartographer_grpc::Run(FLAGS_configuration_directory,
+                         FLAGS_configuration_basename);
+}

cartographer_grpc/map_builder_server_options.cc

@@ -30,7 +30,8 @@ proto::MapBuilderServerOptions CreateMapBuilderServerOptions(
   map_builder_server_options.set_num_grpc_threads(
       lua_parameter_dictionary->GetInt("num_grpc_threads"));
   *map_builder_server_options.mutable_map_builder_options() =
-      cartographer::mapping::CreateMapBuilderOptions(lua_parameter_dictionary);
+      cartographer::mapping::CreateMapBuilderOptions(
+          lua_parameter_dictionary->GetDictionary("map_builder").get());
   return map_builder_server_options;
 }
 

configuration_files/map_builder_server.lua

@@ -0,0 +1,23 @@
+-- Copyright 2017 The Cartographer Authors
+--
+-- Licensed under the Apache License, Version 2.0 (the "License");
+-- you may not use this file except in compliance with the License.
+-- You may obtain a copy of the License at
+--
+--      http://www.apache.org/licenses/LICENSE-2.0
+--
+-- Unless required by applicable law or agreed to in writing, software
+-- distributed under the License is distributed on an "AS IS" BASIS,
+-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+-- See the License for the specific language governing permissions and
+-- limitations under the License.
+
+include "map_builder.lua"
+
+options = {
+  server_address = "0.0.0.0:50051",
+  num_grpc_threads = 4,
+  map_builder = MAP_BUILDER,
+}
+
+return options