SingleThreadedExecutor spin_once_until_future_complete does not spin until future is complete

[ErikOrjehag]

Bug report

Required Info:

• Operating System:
  • Ubuntu 20.04.2 LTS
• Installation type:
  • Binary
• Version or commit hash:
  • Galactic (code looks the same in Rolling)
• DDS implementation:
  • Galactic default
• Client library (if applicable):
  • rclpy

Steps to reproduce issue

Call a service twice from a python node with a SingleThreadedExecutor like this:

future = my_service_client.call_async(req)
executor.spin_once_until_future_complete(future)
res = future.result()

Expected behavior

First time the res.done() == True, the second time res.done() == True.

Actual behavior

First time the res.done() == True, the second time res.done() == False.

Additional information

The implementation here looks strange to me https://github.com/ros2/rclpy/blob/fb1058935f25f20a5ba9552994b9b63a3edd36f9/rclpy/rclpy/executors.py#L727

If I replace:

executor.spin_once_until_future_complete(future)

with

while not future.done():
    executor.spin_once()

my example works as expected. Should there not be a loop that waits to see if the future is complete? What do you think? How come it works the first time I call the service and not the second time I call the service?

[fujitatomoya]

related to https://github.com/ros2/rclpy/issues/989?

[fujitatomoya]

my example works as expected. Should there not be a loop that waits to see if the future is complete?

No i do not think so, that does not seem to be the intention of this method.

[ErikOrjehag]

No i do not think so, that does not seem to be the intention of this method.

But for the MultiThreadedExecutor there is a wait_condition on future.done https://github.com/ros2/rclpy/blob/fb1058935f25f20a5ba9552994b9b63a3edd36f9/rclpy/rclpy/executors.py#L782

[fujitatomoya]

@ErikOrjehag i mean that your expectation is correct, this seems to be a bug for me. sorry for the confusion 😅

[angel-ayala]

Can this be related to the inexistence of the Executor when the Future class is created? Since when I check for future.done() the process freeze up