LaunchConfiguration is not read from ComposableNode when included inside a group action

[jacobperron]

Bug report

Required Info:

• Operating System:
  • Ubuntu 18.04
• Installation type:
  • source
• Version or commit hash:
  • c5e2aa2
• DDS implementation:
  • N/A
• Client library (if applicable):
  • N/A

Steps to reproduce issue

Create the following two launch files:

foo.launch.xml

<launch>
  <group>
    <include file='bar.launch.py'>
    </include>
  </group>
</launch>

bar.launch.py

import launch
import launch_ros


def generate_launch_description():
    return launch.LaunchDescription([
        launch.actions.DeclareLaunchArgument(name='bar_arg', default_value='True'),
        launch_ros.actions.ComposableNodeContainer(
            package='rclcpp_components', node_executable='component_container',
            node_name='my_container', node_namespace='',
            composable_node_descriptions=[
                launch_ros.descriptions.ComposableNode(
                    package='demo_nodes_cpp',
                    node_plugin='demo_nodes_cpp::Talker',
                    parameters=[{'use_sim_time': launch.substitutions.LaunchConfiguration('bar_arg')}]
                ),
            ]
        ),
        # launch_ros.actions.Node(
        #     name='talker', package='demo_nodes_cpp', node_executable='talker', output='screen',
        #     parameters=[{'use_sim_time': launch.substitutions.LaunchConfiguration('bar_arg')}]),
    ])

Launch foo.launch.xml:

ros2 launch foo.launch.xml

Expected behavior

No launch errors.

Actual behavior

Launch error:

[INFO] [launch]: All log files can be found below /home/jacob/.ros/log/2020-01-16-13-53-42-380127-warner-9368
[INFO] [launch]: Default logging verbosity is set to INFO
[INFO] [component_container-1]: process started with pid [9379]
[ERROR] [launch]: Caught exception in launch (see debug for traceback): launch configuration 'bar_arg' does not exist
[INFO] [component_container-1]: sending signal 'SIGINT' to process[component_container-1]
[INFO] [component_container-1]: process has finished cleanly [pid 9379]

Debug output

[DEBUG] [launch.launch_context]: emitting event synchronously: 'launch.events.IncludeLaunchDescription'
[DEBUG] [launch.launch_context]: emitting event synchronously: 'launch.events.IncludeLaunchDescription'
[INFO] [launch]: All log files can be found below /home/jacob/.ros/log/2020-01-16-13-54-08-734132-warner-9451
[INFO] [launch]: Default logging verbosity is set to DEBUG
[DEBUG] [launch]: processing event: ''
[DEBUG] [launch]: processing event: '' ✓ ''
[DEBUG] [launch]: processing event: ''
[DEBUG] [launch]: processing event: '' ✓ ''
[INFO] [component_container-1]: process started with pid [9462]
[DEBUG] [launch.launch_context]: emitting event: 'launch.events.process.ProcessStarted'
[DEBUG] [launch]: processing event: ''
[DEBUG] [launch]: processing event: '' ✓ ''
Executing () created at /usr/lib/python3.6/asyncio/queues.py:74> took 0.252 seconds
[DEBUG] [launch]: Traceback (most recent call last):
  File "/opt/ros/eloquent/lib/python3.6/site-packages/launch/launch_service.py", line 381, in run_async
    await process_one_event_task
  File "/usr/lib/python3.6/asyncio/coroutines.py", line 126, in send
    return self.gen.send(value)
  File "/opt/ros/eloquent/lib/python3.6/site-packages/launch/launch_service.py", line 291, in _process_one_event
    await self.__process_event(next_event)
  File "/usr/lib/python3.6/asyncio/coroutines.py", line 110, in __next__
    return self.gen.send(None)
  File "/opt/ros/eloquent/lib/python3.6/site-packages/launch/launch_service.py", line 311, in __process_event
    visit_all_entities_and_collect_futures(entity, self.__context))
  File "/opt/ros/eloquent/lib/python3.6/site-packages/launch/utilities/visit_all_entities_and_collect_futures_impl.py", line 38, in visit_all_entities_and_collect_futures
    sub_entities = entity.visit(context)
  File "/opt/ros/eloquent/lib/python3.6/site-packages/launch/action.py", line 108, in visit
    return self.execute(context)
  File "/opt/ros/eloquent/lib/python3.6/site-packages/launch_ros/actions/load_composable_nodes.py", line 171, in execute
    self._load_in_sequence(self.__composable_node_descriptions, context)
  File "/opt/ros/eloquent/lib/python3.6/site-packages/launch_ros/actions/load_composable_nodes.py", line 151, in _load_in_sequence
    self._load_node(next_composable_node_description, context)
  File "/opt/ros/eloquent/lib/python3.6/site-packages/launch_ros/actions/load_composable_nodes.py", line 114, in _load_node
    context, composable_node_description.parameters
  File "/opt/ros/eloquent/lib/python3.6/site-packages/launch_ros/utilities/evaluate_parameters.py", line 145, in evaluate_parameters
    output_params.append(evaluate_parameter_dict(context, param))
  File "/opt/ros/eloquent/lib/python3.6/site-packages/launch_ros/utilities/evaluate_parameters.py", line 69, in evaluate_parameter_dict
    evaluated_value = perform_substitutions(context, list(value))
  File "/opt/ros/eloquent/lib/python3.6/site-packages/launch/utilities/perform_substitutions_impl.py", line 26, in perform_substitutions
    return ''.join([context.perform_substitution(sub) for sub in subs])
  File "/opt/ros/eloquent/lib/python3.6/site-packages/launch/utilities/perform_substitutions_impl.py", line 26, in 
    return ''.join([context.perform_substitution(sub) for sub in subs])
  File "/opt/ros/eloquent/lib/python3.6/site-packages/launch/launch_context.py", line 184, in perform_substitution
    return substitution.perform(self)
  File "/opt/ros/eloquent/lib/python3.6/site-packages/launch/substitutions/launch_configuration.py", line 99, in perform
    "launch configuration '{}' does not exist".format(expanded_variable_name))
launch.substitutions.substitution_failure.SubstitutionFailure: launch configuration 'bar_arg' does not exist
[ERROR] [launch]: Caught exception in launch (see debug for traceback): launch configuration 'bar_arg' does not exist

[DEBUG] [launch.launch_context]: emitting event: 'launch.events.Shutdown'

[DEBUG] [launch]: processing event: '<launch.events.shutdown.Shutdown object at 0x7fb51d289c88>'

[DEBUG] [launch]: processing event: '<launch.events.shutdown.Shutdown object at 0x7fb51d289c88>' ✓ '<launch.event_handlers.on_shutdown.OnShutdown object at 0x7fb51d2965f8>'

[DEBUG] [launch.launch_context]: emitting event synchronously: 'launch.events.process.SignalProcess'

[DEBUG] [launch]: processing event: '<launch.events.shutdown.Shutdown object at 0x7fb51d289c88>' ✓ '<launch.event_handlers.on_shutdown.OnShutdown object at 0x7fb5204265c0>'

[DEBUG] [launch]: processing event: '<launch.events.shutdown.Shutdown object at 0x7fb51d289c88>' ✓ '<launch.event_handlers.on_shutdown.OnShutdown object at 0x7fb52dde0e10>'

Executing <Task finished coro=<LaunchService._process_one_event() done, defined at /opt/ros/eloquent/lib/python3.6/site-packages/launch/launch_service.py:289> result=None created at /opt/ros/eloquent/lib/python3.6/site-packages/launch/launch_service.py:359> took 0.743 seconds

[DEBUG] [launch]: processing event: '<launch.events.process.signal_process.SignalProcess object at 0x7fb51d343748>'

[DEBUG] [launch]: processing event: '<launch.events.process.signal_process.SignalProcess object at 0x7fb51d343748>' ✓ '<launch.event_handler.EventHandler object at 0x7fb51d296908>'

[INFO] [component_container-1]: sending signal 'SIGINT' to process[component_container-1]

[DEBUG] [launch.launch_context]: emitting event synchronously: 'launch.events.process.ProcessStdout'

[DEBUG] [launch]: processing event: '<launch.events.process.process_stdout.ProcessStdout object at 0x7fb52041cf28>'

[DEBUG] [launch]: processing event: '<launch.events.process.process_stdout.ProcessStdout object at 0x7fb52041cf28>' ✓ '<launch.event_handlers.on_process_io.OnProcessIO object at 0x7fb51d2965c0>'

[INFO] [component_container-1]: process has finished cleanly [pid 9462]

[DEBUG] [launch.launch_context]: emitting event: 'launch.events.process.ProcessExited'

[DEBUG] [launch]: processing event: '<launch.events.process.process_exited.ProcessExited object at 0x7fb52041cdd8>'

[DEBUG] [launch]: processing event: '<launch.events.process.process_exited.ProcessExited object at 0x7fb52041cdd8>' ✓ '<launch.event_handlers.on_process_exit.OnProcessExit object at 0x7fb51d296518>'

[DEBUG] [launch]: processing event: '<launch.events.process.process_exited.ProcessExited object at 0x7fb52041cdd8>' ✓ '<launch.event_handlers.on_process_exit.OnProcessExit object at 0x7fb51d296630>'

Additional information

If we remove the <group> tag in foo.launch.xml, then there is no issue.

If we use a Node action instead of a composable node, then there is no issue.

[wjwwood]

Maybe you need to use the scoped argument for the GroupAction? I need to look in more detail at why you are using the group, but I guess the scope option needs to be flipped or the scope mechanism has a bug in it or something.

[wjwwood]

Maybe it has to do with the delayed evaluation of the substitution? I'm not sure...

[wjwwood]

I think since the load of the composable nodes is done asynchronously (with an event handler) the group has already ended and undone the scope:

launch_ros/launch_ros/launch_ros/actions/composable_node_container.py

Line 73 in c5e2aa2

composable_node_descriptions=self.__composable_node_descriptions,

I'm not sure how to fix this, a few options:

• perform the substitutions in ComposableNodeContainer::execute() before registering the event
• change how the containers are loaded to avoid the delay in evaluating the substitutions (i.e. do not use an event)
• store the launch config state and make sure it is used for the evaluation in the event handler (sort of like lambda capture or something)

[jrgnicho]

Also experiencing the same issue with ComposableNodeContainer where my python launch file looks like this

def generate_launch_description():
   
    container =  ComposableNodeContainer(
            node_name= 'perception',
            node_namespace= launch.substitutions.LaunchConfiguration('global_ns'),
            package= 'rclcpp_components',
            node_executable = 'component_container',
            composable_node_descriptions = [
                ComposableNode(
                package='crs_perception',
                node_plugin='crs_perception::LocalizeToPart',
                node_name='part_localization',
                node_namespace = launch.substitutions.LaunchConfiguration('global_ns')),
                ],
            output = 'screen'
        )    
    
    return launch.LaunchDescription([
        launch.actions.DeclareLaunchArgument('global_ns', default_value = ['/my_ns']),
        container])

It runs fine when I call it from the command line
but when I call it from an xml launch file

	    <include file="$(find-pkg-share crs_application)/launch/perception.launch.py">
	    	<arg name="global_ns" value="$(var group_ns)"/>
	    </include>

It errors out saying that the launch configuration 'global_ns' does not exist. Removing the argument has no effect either

[jacobperron]

I did some investigation and I can confirm the launch configuration dropped by the event handler:

launch_ros/launch_ros/launch_ros/actions/composable_node_container.py

Lines 95 to 105 in 8c05ebb

	RegisterEventHandler(
	event_handler=OnProcessStart(
	target_action=self,
	on_start=[
	LoadComposableNodes(
	composable_node_descriptions=self.__composable_node_descriptions,
	target_container=self
	)
	]
	)
	)

Looking through the commit history, the whole event handler strategy for loading seems vestigial; it was originally used in the LoadComposableNodes action, but since moved to the container action (see #16). I don't think it is necessary to use an event and we can simply return the load node action. See #170 for proposed fix.