From 5bb81a9b4ad8bca009b4b86b24fa08de311e63fa Mon Sep 17 00:00:00 2001
From: gaschler <gaschlera@gmail.com>
Date: Mon, 18 Dec 2017 17:12:29 +0100
Subject: [PATCH] correct MapBuilderStub (#770)

Context: The `::grpc::ClientContext` represents a single RPC on the client side. Therefore it is illegal to share the same context between two different RPC invocations.
---
 cartographer_grpc/mapping/map_builder_stub.cc | 6 ++++--
 cartographer_grpc/mapping/map_builder_stub.h  | 1 -
 2 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/cartographer_grpc/mapping/map_builder_stub.cc b/cartographer_grpc/mapping/map_builder_stub.cc
index 565a64c..46f1dfa 100644
--- a/cartographer_grpc/mapping/map_builder_stub.cc
+++ b/cartographer_grpc/mapping/map_builder_stub.cc
@@ -33,6 +33,7 @@ int MapBuilderStub::AddTrajectoryBuilder(
     const cartographer::mapping::proto::TrajectoryBuilderOptions&
         trajectory_options,
     LocalSlamResultCallback local_slam_result_callback) {
+  grpc::ClientContext client_context;
   proto::AddTrajectoryRequest request;
   proto::AddTrajectoryResponse result;
   *request.mutable_trajectory_builder_options() = trajectory_options;
@@ -40,7 +41,7 @@ int MapBuilderStub::AddTrajectoryBuilder(
     *request.add_expected_sensor_ids() = sensor_id;
   }
   grpc::Status status =
-      service_stub_->AddTrajectory(&client_context_, request, &result);
+      service_stub_->AddTrajectory(&client_context, request, &result);
   CHECK(status.ok());
 
   // Construct trajectory builder stub.
@@ -62,11 +63,12 @@ MapBuilderStub::GetTrajectoryBuilder(int trajectory_id) const {
 }
 
 void MapBuilderStub::FinishTrajectory(int trajectory_id) {
+  grpc::ClientContext client_context;
   proto::FinishTrajectoryRequest request;
   google::protobuf::Empty response;
   request.set_trajectory_id(trajectory_id);
   grpc::Status status =
-      service_stub_->FinishTrajectory(&client_context_, request, &response);
+      service_stub_->FinishTrajectory(&client_context, request, &response);
   CHECK(status.ok());
   trajectory_builder_stubs_.erase(trajectory_id);
 }
diff --git a/cartographer_grpc/mapping/map_builder_stub.h b/cartographer_grpc/mapping/map_builder_stub.h
index 80c7bb8..bdddca8 100644
--- a/cartographer_grpc/mapping/map_builder_stub.h
+++ b/cartographer_grpc/mapping/map_builder_stub.h
@@ -53,7 +53,6 @@ class MapBuilderStub : public cartographer::mapping::MapBuilderInterface {
   cartographer::mapping::PoseGraphInterface* pose_graph() override;
 
  private:
-  grpc::ClientContext client_context_;
   std::shared_ptr<grpc::Channel> client_channel_;
   std::unique_ptr<proto::MapBuilderService::Stub> service_stub_;
   PoseGraphStub pose_graph_stub_;