Executor::spin_some() should check for work only once

[wjwwood]

I believe spin_some behaves contrary to how most people would assume. I believe most people assume that if there are three things to do when you call spin_some() only three things will be done then it would return. Even if new work items come up during that execution.

However, right now spin_some() will check if there is work to do after each work item is completed. This means that if you have more work coming in than you can execute, spin_some() will never exit because there is always something to do.

This could be fixed by "claiming" everything there is to do when spin_some() starts, then executing each of them and then exit. Basically only checking for work one time, at the beginning of the method.

[wjwwood]

This was previous discussed in a related, but ultimately different, issue:

#280 (comment)

[tj10200]

Hey, I'm pretty new to working on github projects. I'd like to take a shot at fixing this issue. Can you give me permission to create branches so I can submit a pull request? Or what is the process there?

[dhood]

Hi @tj10200, rather than giving contributors write access, we ask them to make a pull request from a fork (see https://help.github.com/articles/fork-a-repo/). Let us know if you get stuck at a particular point.

In terms of general contribution workflow, if you'd like to work on this issue you can claim it (as you have done), and comment here for general discussion on the direction of the work, and then once you open a PR we can review the code details.

[tj10200]

Thanks @dhood, I appreciate the help. I submitted a pull request with a minor change on the loop, but maybe I got ahead of myself a bit. Is there a README on how to get the project building. Specifically how to get ament_cmake_ros and ament_cmake projects integrated so the CMakeLists can find them?

[wjwwood]

@tj10200 there are quite a few dependencies for rclcpp, I'd recommend follow our ROS 2 development setup here:

https://github.com/ros2/ros2/wiki/Installation#building-from-source (use one of the ones from the "Building from Source" list)

Then you'll be able to build and test only rclcpp using the --only rclcpp argument to our build tool (ament.py build). There's also these references:

• https://github.com/ros2/ros2/wiki/Ament-Tutorial#run-the-build
• https://github.com/ros2/ros2/wiki/Ament-Tutorial#run-the-tests
• https://github.com/ros2/ros2/wiki/Contributing#contributing-code

[tj10200]

Hi, @wjwwood. I've gone through a few iterations of trying to get the code to build using the guides you provided and keep getting stuck on this compilation error in the rclcpp project:

service.hpp:128:71: error: there are no arguments to ‘rcl_node_get_logger_name’ that depend on a template parameter, so a declaration of ‘rcl_node_get_logger_name’ must be available [-fpermissive]
rclcpp::get_logger(rcl_node_get_logger_name(handle.get())).get_child("rclcpp")

I can't find any definition of rcl_node_get_logger_name so I assume this must be some environmental thing I am missing.

I am on a Ubuntu 16.04 desktop VM. The guide said this was the supported version.
gcc 5.4.0
cmake 3.5.1

Any thoughts?

[mikaelarguedas]

rcl_get_logger_name has been added after the Ardent release, so my guess is that you;re using an old version of the code.

Can you try to build the entire stack from source following these instructions ?
In the step "Get ROS 2.0 code", make sure to get the ros2.repos file from the master branch, i.e:
replace release-latest with masterin the URL.
before: wget https://raw.githubusercontent.com/ros2/ros2/release-latest/ros2.repos
after: wget https://raw.githubusercontent.com/ros2/ros2/master/ros2.repos

HTH

[tj10200]

Thanks all, I got the code building. It was a combination of not using master and the rviz directory not building on my VM which led to missing cmake dependencies when I went back and tried to use --only rclcpp.

[oswinso]

Is this still in progress? I'd like to take this up if nobody is working on this right now.