Multithreaded topics sometimes don't respond #368
Description
Bug report
Required Info:
- Operating System:
Ubuntu 22.04 humble - Installation type:
binaries - Version or commit hash:
Output of git rev-parse HEAD, release version, or repos file - DDS implementation:
rmw_implementation used Fast-RTPS - Client library (if applicable):
rclcpp
Steps to reproduce issue
I change https://github.com/ros2/examples/blob/humble/rclcpp/executors/multithreaded_executor/multithreaded_executor.cpp this demo , stop the timer and build another node to publish , but sometime the Subscription do not work . I do not sure the Subscription not received or some other error
Subscription
#include <chrono>
#include <functional>
#include <memory>
#include <string>
#include <thread>
#include "rclcpp/rclcpp.hpp"
#include "std_msgs/msg/string.hpp"
using namespace std::chrono_literals;
/**
* A small convenience function for converting a thread ID to a string
**/
std::string string_thread_id()
{
auto hashed = std::hash<std::thread::id>()(std::this_thread::get_id());
return std::to_string(hashed);
}
class DualThreadedNode : public rclcpp::Node
{
public:
DualThreadedNode()
: Node("DualThreadedNode")
{
/* These define the callback groups
* They don't really do much on their own, but they have to exist in order to
* assign callbacks to them. They're also what the executor looks for when trying to run multiple threads
*/
callback_group_subscriber1_ = this->create_callback_group(
rclcpp::CallbackGroupType::MutuallyExclusive);
callback_group_subscriber2_ = this->create_callback_group(
rclcpp::CallbackGroupType::MutuallyExclusive);
// Each of these callback groups is basically a thread
// Everything assigned to one of them gets bundled into the same thread
auto sub1_opt = rclcpp::SubscriptionOptions();
sub1_opt.callback_group = callback_group_subscriber1_;
auto sub2_opt = rclcpp::SubscriptionOptions();
sub2_opt.callback_group = callback_group_subscriber2_;
subscription1_ = this->create_subscription<std_msgs::msg::String>(
"topic",
rclcpp::QoS(10),
// std::bind is sort of C++'s way of passing a function
// If you're used to function-passing, skip these comments
std::bind(
&DualThreadedNode::subscriber1_cb, // First parameter is a reference to the function
this, // What the function should be bound to
std::placeholders::_1), // At this point we're not positive of all the
// parameters being passed
// So we just put a generic placeholder
// into the binder
// (since we know we need ONE parameter)
sub1_opt); // This is where we set the callback group.
// This subscription will run with callback group subscriber1
subscription2_ = this->create_subscription<std_msgs::msg::String>(
"topic",
rclcpp::QoS(10),
std::bind(
&DualThreadedNode::subscriber2_cb,
this,
std::placeholders::_1),
sub2_opt);
}
private:
/**
* Simple function for generating a timestamp
* Used for somewhat ineffectually demonstrating that the multithreading doesn't cripple performace
*/
std::string timing_string()
{
rclcpp::Time time = this->now();
return std::to_string(time.nanoseconds());
}
/**
* Every time the Publisher publishes something, all subscribers to the topic get poked
* This function gets called when Subscriber1 is poked (due to the std::bind we used when defining it)
*/
void subscriber1_cb(const std_msgs::msg::String::ConstSharedPtr msg)
{
auto message_received_at = timing_string();
// Extract current thread
RCLCPP_INFO(
this->get_logger(), "THREAD %s => Heard '%s' at %s",
string_thread_id().c_str(), msg->data.c_str(), message_received_at.c_str());
}
/**
* This function gets called when Subscriber2 is poked
* Since it's running on a separate thread than Subscriber 1, it will run at (more-or-less) the same time!
*/
void subscriber2_cb(const std_msgs::msg::String::ConstSharedPtr msg)
{
auto message_received_at = timing_string();
// Prep display message
RCLCPP_INFO(
this->get_logger(), "THREAD %s => Heard '%s' at %s",
string_thread_id().c_str(), msg->data.c_str(), message_received_at.c_str());
}
rclcpp::CallbackGroup::SharedPtr callback_group_subscriber1_;
rclcpp::CallbackGroup::SharedPtr callback_group_subscriber2_;
rclcpp::Subscription<std_msgs::msg::String>::SharedPtr subscription1_;
rclcpp::Subscription<std_msgs::msg::String>::SharedPtr subscription2_;
};
int main(int argc, char * argv[])
{
rclcpp::init(argc, argv);
// You MUST use the MultiThreadedExecutor to use, well, multiple threads
rclcpp::executors::MultiThreadedExecutor executor;
auto subnode = std::make_shared<DualThreadedNode>(); // This contains BOTH subscriber callbacks.
// They will still run on different threads
// One Node. Two callbacks. Two Threads
executor.add_node(subnode);
executor.spin();
rclcpp::shutdown();
return 0;
}
Publisher
// Created by ubuntu on 23-11-28.
//
#include <chrono>
#include <functional>
#include <memory>
#include "rclcpp/rclcpp.hpp"
#include "std_msgs/msg/string.hpp"
#include "std_msgs/msg/bool.hpp"
#include <std_msgs/msg/string.hpp>
using namespace std::chrono_literals;
using std::placeholders::_1;
class ChangeWorkFrame: public rclcpp::Node
{
public:
ChangeWorkFrame();
void change_work_frame_programe();
private:
rclcpp::Publisher<std_msgs::msg::String>::SharedPtr publisher_;
size_t count_;
};
void ChangeWorkFrame::change_work_frame_programe()
{
std_msgs::msg::String change_work_frame;
change_work_frame.data = "sss" + std::to_string(this->count_++);
RCLCPP_INFO(this->get_logger(), " Publishing '%s'", change_work_frame.data.c_str());
this->publisher_->publish(change_work_frame);
}
/***********************************************end**************************************************/
ChangeWorkFrame::ChangeWorkFrame():rclcpp::Node("changeframe")
{
publisher_ = this->create_publisher<std_msgs::msg::String>("topic", 10);
sleep(2);
change_work_frame_programe();
}
/***********************************************end**************************************************/
int main(int argc, char** argv)
{
rclcpp::init(argc, argv);
rclcpp::spin(std::make_shared<ChangeWorkFrame>());
rclcpp::shutdown();
return 0;
}
Expected behavior
When I run the Publisher node the Subscription node will response.
Actual behavior
Sometimes Subscription not response.
Additional information
I want to use the multithreaded_executor in real scene like this response mechanism ，but when I try it have this problem .
Sincere thanks
Kaola