├── CMakeLists.txt ├── LICENSE ├── README.md ├── cyclonedds.xml ├── msg └── ShmTopic.msg ├── package.xml └── src ├── iox_subscriber.cpp ├── listener.cpp └── talker.cpp /CMakeLists.txt: -------------------------------------------------------------------------------- 1 | cmake_minimum_required(VERSION 3.8) 2 | project(ros2_shm_demo) 3 | 4 | if(CMAKE_COMPILER_IS_GNUCXX OR CMAKE_CXX_COMPILER_ID MATCHES "Clang") 5 | add_compile_options(-Wall -Wextra -Wpedantic) 6 | endif() 7 | 8 | # find dependencies 9 | find_package(ament_cmake REQUIRED) 10 | find_package(rosidl_default_generators REQUIRED) 11 | find_package(rclcpp REQUIRED) 12 | 13 | # only needed to build a separate iceoryx subscriber 14 | # which is used to verify Shared Memory communication 15 | find_package(iceoryx_posh CONFIG REQUIRED) 16 | 17 | include_directories(include) 18 | 19 | set(msg_files 20 | "msg/ShmTopic.msg" 21 | ) 22 | 23 | rosidl_generate_interfaces(${PROJECT_NAME} 24 | ${msg_files} 25 | ) 26 | 27 | ament_export_dependencies(rosidl_default_runtime) 28 | 29 | add_executable(talker 30 | src/talker.cpp 31 | ) 32 | 33 | ament_target_dependencies(talker 34 | "rclcpp" 35 | ) 36 | 37 | # we want to use the messages from the same package 38 | # would not be needed if we build the messages in a separate package 39 | rosidl_target_interfaces(talker 40 | ${PROJECT_NAME} "rosidl_typesupport_cpp") 41 | 42 | install(TARGETS talker 43 | DESTINATION lib/${PROJECT_NAME}) 44 | 45 | add_executable(listener 46 | src/listener.cpp 47 | ) 48 | 49 | ament_target_dependencies(listener 50 | "rclcpp" 51 | ) 52 | 53 | rosidl_target_interfaces(listener 54 | ${PROJECT_NAME} "rosidl_typesupport_cpp") 55 | 56 | install(TARGETS listener 57 | DESTINATION lib/${PROJECT_NAME}) 58 | 59 | # we build an iceoryx subscriber app that also listens to the topic 60 | add_executable(iox_subscriber 61 | src/iox_subscriber.cpp 62 | ) 63 | 64 | target_link_libraries(iox_subscriber 65 | iceoryx_posh::iceoryx_posh 66 | ) 67 | 68 | rosidl_target_interfaces(iox_subscriber 69 | ${PROJECT_NAME} "rosidl_typesupport_cpp") 70 | 71 | install(TARGETS iox_subscriber 72 | DESTINATION lib/${PROJECT_NAME}) 73 | 74 | if(BUILD_TESTING) 75 | find_package(ament_lint_auto REQUIRED) 76 | # the following line skips the linter which checks for copyrights 77 | # uncomment the line when a copyright and license is not present in all source files 78 | #set(ament_cmake_copyright_FOUND TRUE) 79 | # the following line skips cpplint (only works in a git repo) 80 | # uncomment the line when this package is not in a git repo 81 | #set(ament_cmake_cpplint_FOUND TRUE) 82 | ament_lint_auto_find_test_dependencies() 83 | endif() 84 | 85 | ament_package() 86 | -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | Apache License 2 | Version 2.0, January 2004 3 | http://www.apache.org/licenses/ 4 | 5 | TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 6 | 7 | 1. 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We also recommend that a 185 | file or class name and description of purpose be included on the 186 | same "printed page" as the copyright notice for easier 187 | identification within third-party archives. 188 | 189 | Copyright [yyyy] [name of copyright owner] 190 | 191 | Licensed under the Apache License, Version 2.0 (the "License"); 192 | you may not use this file except in compliance with the License. 193 | You may obtain a copy of the License at 194 | 195 | http://www.apache.org/licenses/LICENSE-2.0 196 | 197 | Unless required by applicable law or agreed to in writing, software 198 | distributed under the License is distributed on an "AS IS" BASIS, 199 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 200 | See the License for the specific language governing permissions and 201 | limitations under the License. 202 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # ros2_shm_demo 2 | This example demonstrates how to use zero-copy Shared Memory data transfer in ROS 2. The middleware used is Eclipse CycloneDDS which integrates Eclipse iceoryx for Shared Memory transfer. 3 | 4 | Since it uses char arrays for its payload data, the example can easily be generalized to arbitrary data such as images and point clouds. 5 | 6 | Currently the ROS message types are limited to fixed-size data types and only a subset of [QoS settings](https://github.com/ros2/rmw_cyclonedds/blob/master/shared_memory_support.md#QoS-settings) is supported. 7 | 8 | ## Installation 9 | 10 | Install ROS 2 Galactic from source as described in https://docs.ros.org/en/galactic/Installation.html. 11 | 12 | Clone this repository into the src folder of your ROS 2 workspace and run: 13 | 14 | ```sh 15 | ~ros2_galactic_ws$ colcon build 16 | ``` 17 | 18 | ## Run the example 19 | 20 | In the ROS 2 workspace in all terminals: 21 | 22 | ```sh 23 | ~/ros2_galactic_ws$ source install/setup.bash 24 | ``` 25 | 26 | In different terminals. 27 | 28 | Run the RouDi middleware daemon 29 | 30 | ```sh 31 | ~/ros2_galactic_ws$ iox-roudi 32 | ``` 33 | 34 | Start the talker 35 | 36 | ```sh 37 | ~/ros2_galactic_ws$ export CYCLONEDDS_URI=file://$PWD/src/ros2_shm_demo/cyclonedds.xml 38 | ~/ros2_galactic_ws$ ros2 run ros2_shm_demo talker 39 | ``` 40 | 41 | Start the listener 42 | 43 | ```sh 44 | ~/ros2_galactic_ws$ export CYCLONEDDS_URI=file://$PWD/src/ros2_shm_demo/cyclonedds.xml 45 | ~/ros2_galactic_ws$ ros2 run ros2_shm_demo listener 46 | ``` 47 | 48 | ## Valdiate Shared Memory usage 49 | 50 | ### Using the introspection 51 | 52 | Build the [iceoryx introspection](https://github.com/ros2/rmw_cyclonedds/blob/master/shared_memory_support.md#Using-the-iceoryx-introspection). 53 | 54 | Note that this is only supported unofficially and hence we build it manually without colcon. 55 | 56 | Run the RouDi as in the steps before but do not start the talker and listener yet. 57 | 58 | In another terminal navigate to the folder where the introspection client was build and run 59 | 60 | ```sh 61 | cd src/eclipse-iceoryx/iceoryx/tools/introspection/build 62 | ~/ros2_galactic_ws/src/eclipse-iceoryx/iceoryx/tools/introspection/build$ ./iox-introspection-client --all 63 | ``` 64 | 65 | Now start the talker and listener as in [the example section](#Run-the-example). 66 | 67 | When talker or listener are started the introspection detects new processes and publisher or subscriber ports. 68 | While the talker is running you should see an increase in mempool usage of a specific size up to *PubHistoryCapacity* as defined in the configuration file. This happens because the publisher stores these samples in Shared Memory for late-joining subscribers. 69 | 70 | If the listener is running as well this could increase to *SubQueueCapacity*, but only if the listener would not take the data almost immediately. Since this is what happens with event-driven subscriptions in ROS 2 we will not observe this. 71 | 72 | ### Eavesdropping with an iceoryx subscriber 73 | 74 | Now we can also start a native iceoryx subscriber to verify data is transmitted via Shared Memory. 75 | Such a subscriber is build by this project for verification purposes. Note that it currently has to rely on some implementation details of CycloneDDS and hence may not work if these change. 76 | 77 | The idea is that it is possible to have an iceoryx subscriber to the specific topic name (which we can extract from the introspection) and also receive dthe data send by the talker via this subscriber. 78 | 79 | To interpret the data, it is important to know what exactly is send and how it is serialized. In this case no serialization happens but CycloneDDS adds some header information before the actual data which we need to account for. The talker sends a samples of type ```ros2_shm_demo::msg::ShmTopic``` (the ROS type) with some 56 byte header prefix. We thus can take an offset of 56 bytes from the data we receive and interpret the sample as the ROS type (cf. *iox_subscriber.cpp*). 80 | 81 | Note that the size of the header may change and it is not part of the CycloneDDS interface hence the iox_subscriber is tied to the current version of CycloneDDS. Since iceoryx now provides a specific interface for user headers like this, this compsensation for the header will not be necessary in the future. This would also allow to use a typed iceoryx subscriber. 82 | 83 | We can run the example together with the introsepction as before, but now we will also start the iox_subscriber in another terminal. 84 | 85 | ```sh 86 | ~/ros2_galactic_ws$ ros2 run ros2_shm_demo iox_subscriber 87 | ``` 88 | 89 | The iceoryx subscriber receives the same data as the listener, but only if the talker sends it using Shared Memory. 90 | If we start the talker with a Shared Memory configuration, we can observe that the data is actually send with iceoryx Shared Memory. 91 | 92 | Conversely, not activating the configuration with 93 | 94 | ```sh 95 | ~/ros2_galactic_ws$ export CYCLONEDDS_URI=file://$PWD/src/ros2_shm_demo/cyclonedds.xml 96 | ``` 97 | 98 | before starting the talker will lead to sending the data over the network and the iceoryx subscriber will not receive any data. If this is the case, the introspection will not show any iceoryx publisher or subscriber (except for the built-in ones, which are used for the introspection itself). 99 | -------------------------------------------------------------------------------- /cyclonedds.xml: -------------------------------------------------------------------------------- 1 | 2 | 3 | 4 | 5 | true 6 | 256 7 | 16 8 | 16 9 | info 10 | 11 | 12 | -------------------------------------------------------------------------------- /msg/ShmTopic.msg: -------------------------------------------------------------------------------- 1 | # For Shared Memory demonstration 2 | # 3 | # Note that we cannot use unbounded strings like 4 | # string data 5 | # for shared memory transfer 6 | # 7 | # string[256] data 8 | # is possible but the generated type is more cumbersome to use 9 | # 10 | # A generic char array allows passing arbitrary data. 11 | # 12 | char[256] data 13 | uint8 size 14 | uint64 counter 15 | 16 | uint8 MAX_SIZE=255 -------------------------------------------------------------------------------- /package.xml: -------------------------------------------------------------------------------- 1 | 2 | 3 | 4 | ros2_shm_demo 5 | 0.14.3 6 | 7 | Show how to use Shared Memory in ROS 2 with CycloneDDS and iceoryx as middleware. 8 | 9 | Matthias Killat 10 | Apache License 2.0 11 | Matthias Killat 12 | 13 | ament_cmake 14 | rosidl_default_generators 15 | 16 | rclcpp 17 | iceoryx_posh 18 | 19 | rclcpp 20 | rosidl_default_runtime 21 | iceoryx_posh 22 | 23 | ament_lint_auto 24 | ament_lint_common 25 | 26 | rosidl_interface_packages 27 | 28 | 29 | ament_cmake 30 | 31 | 32 | -------------------------------------------------------------------------------- /src/iox_subscriber.cpp: -------------------------------------------------------------------------------- 1 | // Copyright 2021 Apex.AI, Inc. 2 | // 3 | // Licensed under the Apache License, Version 2.0 (the "License"); 4 | // you may not use this file except in compliance with the License. 5 | // You may obtain a copy of the License at 6 | // 7 | // http://www.apache.org/licenses/LICENSE-2.0 8 | // 9 | // Unless required by applicable law or agreed to in writing, software 10 | // distributed under the License is distributed on an "AS IS" BASIS, 11 | // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 | // See the License for the specific language governing permissions and 13 | // limitations under the License. 14 | 15 | #include "ros2_shm_demo/msg/shm_topic.hpp" 16 | 17 | #include "iceoryx_posh/popo/untyped_subscriber.hpp" 18 | #include "iceoryx_posh/runtime/posh_runtime.hpp" 19 | #include "iceoryx_utils/posix_wrapper/signal_handler.hpp" 20 | 21 | #include 22 | 23 | // Internally CycloneDDS prefixes the data with a header and we have to 24 | // account for this. 25 | // We do not want dependencies to DDS here, hence it is hard-coded 26 | // This is only for demo purposes and should not be done in production code! 27 | // In the future CycloneDDS will use the new user header provided by iceoryx 28 | // instead. 29 | constexpr uint32_t DDS_IOX_HEADER_SIZE = 56; 30 | using ROSTopic = ros2_shm_demo::msg::ShmTopic; 31 | 32 | bool shutdown = false; 33 | constexpr char APP_NAME[] = "iox-ros2-subscriber"; 34 | 35 | static void sigHandler(int) { 36 | // caught SIGINT or SIGTERM, now exit gracefully 37 | shutdown = true; 38 | } 39 | 40 | int main() { 41 | // register sigHandler 42 | auto signalIntGuard = 43 | iox::posix::registerSignalHandler(iox::posix::Signal::INT, sigHandler); 44 | auto signalTermGuard = 45 | iox::posix::registerSignalHandler(iox::posix::Signal::TERM, sigHandler); 46 | 47 | // initialize runtime 48 | iox::runtime::PoshRuntime::initRuntime(APP_NAME); 49 | 50 | // initialize subscriber 51 | // we know how the services are mapped to dds 52 | // note that we can use the introspection to get this info 53 | // Note: If not for the internal header C(payload) + DDS_IOX_HEADER_SIZE; 73 | 74 | // we account for the header CycloneDDS currently prepends before the 75 | // actual ROS sample 76 | const ROSTopic *sample = 77 | reinterpret_cast(payloadWithoutDDSHeader); 78 | auto data = reinterpret_cast(sample->data.data()); 79 | 80 | std::cout << "iox subscriber: Received " << data << " " 81 | << sample->counter << std::endl; 82 | 83 | subscriber.release(payload); 84 | }) 85 | .or_else([](auto &result) { 86 | // only has to be called if the alternative is of 87 | // interest, i.e. if nothing has to happen when no data 88 | // is received and a possible error alternative is not 89 | // checked or_else is not needed 90 | if (result != iox::popo::ChunkReceiveResult::NO_CHUNK_AVAILABLE) { 91 | std::cout << "Error receiving chunk." << std::endl; 92 | } 93 | }); 94 | 95 | // use polling for simplicity 96 | std::this_thread::sleep_for(std::chrono::milliseconds(100)); 97 | } 98 | 99 | return (EXIT_SUCCESS); 100 | } -------------------------------------------------------------------------------- /src/listener.cpp: -------------------------------------------------------------------------------- 1 | // Copyright 2021 Apex.AI, Inc. 2 | // 3 | // Licensed under the Apache License, Version 2.0 (the "License"); 4 | // you may not use this file except in compliance with the License. 5 | // You may obtain a copy of the License at 6 | // 7 | // http://www.apache.org/licenses/LICENSE-2.0 8 | // 9 | // Unless required by applicable law or agreed to in writing, software 10 | // distributed under the License is distributed on an "AS IS" BASIS, 11 | // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 | // See the License for the specific language governing permissions and 13 | // limitations under the License. 14 | 15 | #include 16 | #include 17 | 18 | #include "rclcpp/rclcpp.hpp" 19 | 20 | #include "ros2_shm_demo/msg/shm_topic.hpp" 21 | 22 | class Listener : public rclcpp::Node { 23 | private: 24 | using Topic = ros2_shm_demo::msg::ShmTopic; 25 | 26 | public: 27 | explicit Listener(const rclcpp::NodeOptions &options) 28 | : Node("shm_demo_listener", options) { 29 | 30 | // subscription callback to process arriving data 31 | auto callback = [this](const Topic::SharedPtr msg) -> void { 32 | // Read the message and perform operations accordingly. 33 | // Here we copy the data and display it. 34 | 35 | std::memcpy(m_lastData, msg->data.data(), msg->size); 36 | m_lastData[Topic::MAX_SIZE] = 37 | '\0'; // in case there was no zero termination 38 | 39 | RCLCPP_INFO(this->get_logger(), "Received %s %lu", m_lastData, 40 | msg->counter); 41 | }; 42 | 43 | rclcpp::QoS qos(rclcpp::KeepLast(10)); 44 | m_subscription = create_subscription("chatter", qos, callback); 45 | } 46 | 47 | private: 48 | rclcpp::Subscription::SharedPtr m_subscription; 49 | 50 | char m_lastData[256]; 51 | }; 52 | 53 | int main(int argc, char *argv[]) { 54 | rclcpp::init(argc, argv); 55 | rclcpp::NodeOptions options; 56 | rclcpp::spin(std::make_shared(options)); 57 | rclcpp::shutdown(); 58 | 59 | return 0; 60 | } -------------------------------------------------------------------------------- /src/talker.cpp: -------------------------------------------------------------------------------- 1 | // Copyright 2021 Apex.AI, Inc. 2 | // 3 | // Licensed under the Apache License, Version 2.0 (the "License"); 4 | // you may not use this file except in compliance with the License. 5 | // You may obtain a copy of the License at 6 | // 7 | // http://www.apache.org/licenses/LICENSE-2.0 8 | // 9 | // Unless required by applicable law or agreed to in writing, software 10 | // distributed under the License is distributed on an "AS IS" BASIS, 11 | // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 | // See the License for the specific language governing permissions and 13 | // limitations under the License. 14 | 15 | #include 16 | #include 17 | #include 18 | #include 19 | #include 20 | 21 | #include "rclcpp/rclcpp.hpp" 22 | 23 | #include "ros2_shm_demo/msg/shm_topic.hpp" 24 | 25 | using namespace std::chrono_literals; 26 | 27 | class Talker : public rclcpp::Node { 28 | private: 29 | using Topic = ros2_shm_demo::msg::ShmTopic; 30 | 31 | public: 32 | explicit Talker(const rclcpp::NodeOptions &options) 33 | : Node("shm_demo_talker", options) { 34 | 35 | auto publishMessage = [this]() -> void { 36 | auto loanedMsg = m_publisher->borrow_loaned_message(); 37 | 38 | populateLoanedMessage(loanedMsg); 39 | 40 | m_publisher->publish(std::move(loanedMsg)); 41 | // We gave up ownership and loanedMsg is not supposed to be accessed 42 | // anymore 43 | 44 | m_count++; 45 | }; 46 | 47 | rclcpp::QoS qos(rclcpp::KeepLast(10)); 48 | m_publisher = this->create_publisher("chatter", qos); 49 | 50 | // Use a timer to schedule periodic message publishing. 51 | m_timer = this->create_wall_timer(1s, publishMessage); 52 | } 53 | 54 | private: 55 | uint64_t m_count = 1; 56 | rclcpp::Publisher::SharedPtr m_publisher; 57 | rclcpp::TimerBase::SharedPtr m_timer; 58 | 59 | void populateLoanedMessage(rclcpp::LoanedMessage &loanedMsg) { 60 | Topic &msg = loanedMsg.get(); 61 | 62 | // Create the data. 63 | // In general this will not be constant. 64 | // Ideally we would create it in place but the ROS API does not allow 65 | // that. Therefore we need to copy it to the loaned message. 66 | 67 | std::string payload{"Hello World"}; 68 | 69 | // We can track a quasi dynamic (bounded) size like this to avoid 70 | // copying more data than needed. 71 | msg.size = (uint8_t)std::min(payload.size(), (size_t)Topic::MAX_SIZE); 72 | msg.counter = m_count; 73 | 74 | // Note that msg.data is a std::array generated by the IDL compiler 75 | std::memcpy(msg.data.data(), payload.data(), msg.size); 76 | 77 | RCLCPP_INFO(this->get_logger(), "Publishing %s %lu", payload.c_str(), 78 | msg.counter); 79 | } 80 | }; 81 | 82 | int main(int argc, char *argv[]) { 83 | rclcpp::init(argc, argv); 84 | rclcpp::NodeOptions options; 85 | rclcpp::spin(std::make_shared(options)); 86 | rclcpp::shutdown(); 87 | 88 | return 0; 89 | } --------------------------------------------------------------------------------