service client hangs on wait_for_service

[huchhong]

Bug report

Required Info:

• Operating System:
  • ubuntu 18.04
• Installation type:
  • binary release of crystal

Steps to reproduce issue

I wrote a launch script to launch a service client and service server as listed below:

import os
from launch import LaunchDescription
import launch.actions
import launch_ros.actions


def generate_launch_description():
    return LaunchDescription([
        launch_ros.actions.Node(
            package="examples_rclcpp_minimal_service",
            node_executable="service_main",
            node_name="service_main",
            node_namespace="",
            output="screen",
            parameters=[]
        ),
        launch_ros.actions.Node(
            package="examples_rclcpp_minimal_client",
            node_executable="client_main",
            node_name="client_main",
            node_namespace="",
            output="screen",
            parameters=[]
        )
    ])

Then i ran this script again and again. Most of the time, things are right. But, i also noticed that sometimes client and service would just hang there forever and sometimes after service has responded, client don't react. The output is listed below:

both hang:

[INFO] [launch]: process[service_main-1]: started with pid [76346]
[INFO] [launch]: process[client_main-2]: started with pid [76347]




^C[WARNING] [launch.LaunchService]: user interrupted with ctrl-c (SIGINT)
[INFO] [rclcpp]: signal_handler(signal_value=2)
[INFO] [launch]: process[service_main-1]: process has finished cleanly
[ERROR] [launch]: process[client_main-2] process has died [pid 76347, exit code 1, cmd '/opt/ros/crystal/lib/examples_rclcpp_minimal_client/client_main __node:=client_main __ns:=/'].
[INFO] [rclcpp]: signal_handler(signal_value=2)
[ERROR] [client_main]: service call failed :(

client hangs:

[INFO] [launch]: process[service_main-1]: started with pid [87612]
[INFO] [launch]: process[client_main-2]: started with pid [87613]
[INFO] [service_main]: request: 41 + 1
^C[WARNING] [launch.LaunchService]: user interrupted with ctrl-c (SIGINT)
[INFO] [rclcpp]: signal_handler(signal_value=2)
[ERROR] [client_main]: service call failed :(
[INFO] [launch]: process[service_main-1]: process has finished cleanly
[ERROR] [launch]: process[client_main-2] process has died [pid 87613, exit code 1, cmd '/opt/ros/crystal/lib/examples_rclcpp_minimal_client/client_main __node:=client_main __ns:=/'].
[INFO] [rclcpp]: signal_handler(signal_value=2)

Expected behavior

both client and service works fine every time.

[clalancette]

I just tried this out on the latest Rolling, and I can't seem to make the problem happen. We've improved services quite a lot since crystal, so this may just work now.

Given the age of this issue, I'm going to close it out. If you are still having problems with the latest version of ROS 2, please feel free to open a new issue and we can debug it there.