python - ROS 错误。 "Error processing request: signal only works in main thread"

Question

我正在使用机器人操作系统 (ROS) 并尝试制作一个服务器/客户端，服务器将在其中启动由客户端指定的 ROS 节点。为了执行“启动”，我根据此处的建议使用 roslaunch:http://wiki.ros.org/roslaunch/API%20Usage

我可以在一个窗口中运行 roscore，然后我可以运行可以正常启动的服务器。但是，一旦我尝试通过客户端发送我想要启动的节点名称，我就会收到以下错误:

“错误处理请求:信号仅在主线程中有效”

然后它指向我尚未追踪到的各个区域中的一堆文件。

我已经尝试在我为要启动的节点(在本例中为 turtlesim_node 和 turtle_teleop_key)单独制作的每个启动文件上使用简单的 roslaunch 调用，它们可以正常启动并通过运行 roslaunch [package] turtlesim_launch 来工作.launch 等

下面是我的服务器的代码:

#!/usr/bin/env python
#Filename: primary_server.py

import rospy
import roslaunch
from robot_man.srv import *

class StartUpServer(object):
    def __init__(self):
        self._nodes = []


    def handle_startup(self, names):
        self._temp = names.nodes.split(",") #This reades in the
        # information from the srv file sent by the client and
        # separates each node/package pair

        #This loop separates the input from pairs of 2 corresponding
        # to the package and node names the user inputs
        for i in range(len(self._temp)):
            self._nodes.append(self._temp[i].split())

        #This loop will launch each node that the user has specified
        for package, executable in self._nodes:
            print('package is: {0}, executable is: {1}'.format(package, executable))
            node = roslaunch.core.Node(package, executable)
            launch = roslaunch.scriptapi.ROSLaunch()
            launch.start()

            process = launch.launch(node)
            print('running node: %s'%executable)
        return StartUpResponse(self._nodes) #I will change this later


if __name__ == '__main__':
    rospy.init_node('startup_node')
    server = StartUpServer()
    rospy.Service('startup', StartUp, server.handle_startup)
    print('The servers are up and running')
    rospy.spin()

这是我的客户的代码:

#!/usr/bin/env python
#Filename: primary_client_startup.py

import rospy
from robot_man.srv import *

def main(nodes):
    rospy.wait_for_service('startup')
    proxy = rospy.ServiceProxy('startup', StartUp)
    response = proxy(nodes)
    return response

if __name__ == '__main__':
    nodes = input('Please enter the node packages followed by \
    node names separated by spaces. \n To activate multiple nodes \
    separate entries with a comma > ')
    main(nodes)

这是我的 srv 文件:

#This should be a string of space/comma separated values
string nodes
---
#This should return "success" if node/s start up successfully, else "fail"
string status

最后，这是我为启动 turtle 模拟器而制作的两个启动文件:

turtlesim_launch.launch

<launch>
    <node name="turtlesim_node" pkg="turtlesim" type="turtlesim_node" />
</launch>

turtle_teleop_launch.launch

<launch>
    <node name="turtle_teleop_key" pkg="turtlesim" type="turtle_teleop_key" />
</launch>

我做了一些谷歌搜索，没有发现 ROS 有类似的问题(虽然 Django 等有一些类似的错误，但它们不相关)。

感谢您的帮助!

附言值得注意的是，当错误发生时，我到了第34行(process = launch.launch(node))。

Answer 1

其实就是文档里提到的

您没有从 Python 主线程调用 init_node()。 Python 只允许从主线程注册信号。

看这里rospyOverviewInitialization and Shutdown