ROS2与C++入门教程-Topic Statistics查看话题

说明：

• 介绍如何启用ROS 2 Topic Statistics并查看输出统计数据

步骤：

• 下载示例talker 代码

cd dev_ws/src/cpp_pubsub/src
wget -O member_function_with_topic_statistics.cpp https://raw.githubusercontent.com/ros2/examples/master/rclcpp/topics/minimal_subscriber/member_function_with_topic_statistics.cpp

• 编辑文件member_function_with_topic_statistics.cpp

#include <chrono>
#include <memory>

#include "rclcpp/rclcpp.hpp"
#include "rclcpp/subscription_options.hpp"

#include "std_msgs/msg/string.hpp"

class MinimalSubscriberWithTopicStatistics : public rclcpp::Node
{
public:
  MinimalSubscriberWithTopicStatistics()
  : Node("minimal_subscriber_with_topic_statistics")
  {
    // manually enable topic statistics via options
    auto options = rclcpp::SubscriptionOptions();
    options.topic_stats_options.state = rclcpp::TopicStatisticsState::Enable;

    // configure the collection window and publish period (default 1s)
    options.topic_stats_options.publish_period = std::chrono::seconds(10);

    // configure the topic name (default '/statistics')
    // options.topic_stats_options.publish_topic = "/topic_statistics"

    auto callback = [this](std_msgs::msg::String::SharedPtr msg) {
        this->topic_callback(msg);
      };

    subscription_ = this->create_subscription<std_msgs::msg::String>(
      "topic", 10, callback, options);
  }

private:
  void topic_callback(const std_msgs::msg::String::SharedPtr msg) const
  {
    RCLCPP_INFO(this->get_logger(), "I heard: '%s'", msg->data.c_str());
  }
  rclcpp::Subscription<std_msgs::msg::String>::SharedPtr subscription_;
};

int main(int argc, char * argv[])
{
  rclcpp::init(argc, argv);
  rclcpp::spin(std::make_shared<MinimalSubscriberWithTopicStatistics>());
  rclcpp::shutdown();
  return 0;
}

• 打开CMakeLists.txt文件

add_executable(listener_with_topic_statistics member_function_with_topic_statistics.cpp)
ament_target_dependencies(listener_with_topic_statistics rclcpp std_msgs)

install(TARGETS
  talker
  listener
  listener_with_topic_statistics
  DESTINATION lib/${PROJECT_NAME})

• 使用启用统计信息的节点运行订阅者

ros2 run cpp_pubsub listener_with_topic_statistics

• 运行talker节点

ros2 run cpp_pubsub talker

• 终端应该每 0.5 秒开始发布信息消息，如下所示：

[INFO] [minimal_publisher]: Publishing: "Hello World: 0"
[INFO] [minimal_publisher]: Publishing: "Hello World: 1"
[INFO] [minimal_publisher]: Publishing: "Hello World: 2"
[INFO] [minimal_publisher]: Publishing: "Hello World: 3"
[INFO] [minimal_publisher]: Publishing: "Hello World: 4"

• 侦听器将开始向控制台打印消息，从发布者当时处于的任何消息计数开始，如下所示：

[INFO] [minimal_subscriber_with_topic_statistics]: I heard: "Hello World: 10"
[INFO] [minimal_subscriber_with_topic_statistics]: I heard: "Hello World: 11"
[INFO] [minimal_subscriber_with_topic_statistics]: I heard: "Hello World: 12"
[INFO] [minimal_subscriber_with_topic_statistics]: I heard: "Hello World: 13"
[INFO] [minimal_subscriber_with_topic_statistics]: I heard: "Hello World: 14"

• 查看话题

ros2 topic list

• 打印出以下内容

/parameter_events
/rosout
/statistics
/topic

• 使用RQt将其可视化

• 查看发布话题内容

ros2 topic echo /statistics

---
measurement_source_name: minimal_subscriber_with_topic_statistics
metrics_source: message_age
unit: ms
window_start:
  sec: 1594856666
  nanosec: 931527366
window_stop:
  sec: 1594856676
  nanosec: 930797670
statistics:
- data_type: 1
  data: .nan
- data_type: 3
  data: .nan
- data_type: 2
  data: .nan
- data_type: 5
  data: 0.0
- data_type: 4
  data: .nan
---
measurement_source_name: minimal_subscriber_with_topic_statistics
metrics_source: message_period
unit: ms
window_start:
  sec: 1594856666
  nanosec: 931527366
window_stop:
  sec: 1594856676
  nanosec: 930797670
statistics:
- data_type: 1
  data: 499.2746365105009
- data_type: 3
  data: 500.0
- data_type: 2
  data: 499.0
- data_type: 5
  data: 619.0
- data_type: 4
  data: 0.4463309283488427
---