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Implement node parameters and parameter services #214

Merged
merged 8 commits into from
Aug 16, 2018
Merged

Implement node parameters and parameter services #214

merged 8 commits into from
Aug 16, 2018

Commits on Aug 16, 2018

  1. Implement parameter services. 

    This adds parameter services to rclpy nodes. Like rclcpp nodes, parameter
services are started by default and can be turned off with the
create_node/Node constructor kwarg `start_parameter_services=False`.

Parameters are stored on the Node class via a `_parameters` dict
attribute. The methods following methods have been added to the Node
API.
* `get_parameter(name)`
* `get_parameters(names)`
* `set_parameters(parameters)`
* `set_parameters_atomically(parameters)`

A Parameter class provides a python interface to individual parameters
that is (hopefully) a bit more ergonomic than using the
Parameter-related message types from rcl_interfaces.

Changes forthcoming in later pull requests:
- Add the parameters_changed_callback API
- Take initial parameters from params file argument.
    @nuclearsandwich
    nuclearsandwich committed Aug 16, 2018
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  2. Raise TypeErrors instead of asserting types. 

    When checking for valid arguments in the parameters API raise TypeErrors
rather than asserting on failure.
    @nuclearsandwich
    nuclearsandwich committed Aug 16, 2018
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  3. Enforce parameter types. 

    This commit adds a Parameter.Type.check method which is used to enforce
the declared parameter type at runtime.
    @nuclearsandwich
    nuclearsandwich committed Aug 16, 2018
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  4. Use constants for parameter separator and request depth.

    @nuclearsandwich
    nuclearsandwich committed Aug 16, 2018
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  5. Make a constant for the topic separator and use it.

    @nuclearsandwich
    nuclearsandwich committed Aug 16, 2018
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  6. Use parameters qos profile for parameter services.

    @nuclearsandwich
    nuclearsandwich committed Aug 16, 2018
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  7. Use type_ for Parameter type attribute. 

    Avoids collusion/confusion with type builtin.
    @nuclearsandwich
    nuclearsandwich committed Aug 16, 2018
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  8. Destroy nodes after node creation tests. 

    The test teardown method is calling rclpy.shutdown() before the nodes
created here are destroyed. With the inclusion of parameter services
this is causing the tests to hang after printing the following
exceptions:

    ========================================================================================================================== 7 passed in 0.11 seconds
    Exception ignored in: <bound method Node.__del__ of <rclpy.node.Node object at 0x7fc321e0fd30>>
    Traceback (most recent call last):
      File "/tmp/scree/src/rclpy-mount/rclpy/rclpy/node.py", line 410, in __del__
        self.destroy_node()
      File "/tmp/scree/src/rclpy-mount/rclpy/rclpy/node.py", line 353, in destroy_node
        _rclpy.rclpy_destroy_node_entity(srv.service_handle, self.handle)
    RuntimeError: Failed to fini 'rcl_service_t': rcl node is invalid, rcl instance id does not match, at /tmp/scree/src/ros2/rcl/rcl/src/rcl/node.c:461
    Exception ignored in: <bound method Node.__del__ of <rclpy.node.Node object at 0x7fc320597828>>
    Traceback (most recent call last):
      File "/tmp/scree/src/rclpy-mount/rclpy/rclpy/node.py", line 410, in __del__
        self.destroy_node()
      File "/tmp/scree/src/rclpy-mount/rclpy/rclpy/node.py", line 353, in destroy_node
        _rclpy.rclpy_destroy_node_entity(srv.service_handle, self.handle)
    RuntimeError: Failed to fini 'rcl_service_t': rcl node is invalid, rcl instance id does not match, at /tmp/scree/src/ros2/rcl/rcl/src/rcl/node.c:461
    Exception ignored in: <bound method Node.__del__ of <rclpy.node.Node object at 0x7fc320597b70>>
    Traceback (most recent call last):
      File "/tmp/scree/src/rclpy-mount/rclpy/rclpy/node.py", line 410, in __del__
        self.destroy_node()
      File "/tmp/scree/src/rclpy-mount/rclpy/rclpy/node.py", line 353, in destroy_node
        _rclpy.rclpy_destroy_node_entity(srv.service_handle, self.handle)
    RuntimeError: Failed to fini 'rcl_service_t': rcl node is invalid, rcl instance id does not match, at /tmp/scree/src/ros2/rcl/rcl/src/rcl/node.c:461

Destroying the nodes before the teardown runs resolves both the
indefinite hang and the exceptions.
    @nuclearsandwich
    nuclearsandwich committed Aug 16, 2018
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