introspection

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Description

A comprehensive ROS2 demo combining both a service client and server to demonstrate service introspection capabilities. The node shows how to configure and use service introspection to monitor service calls, enabling developers to observe metadata and contents of service requests and responses through the /_service_event topic.

The demo includes two internal nodes:

  • IntrospectionServiceNode: Provides the add_two_ints service

  • IntrospectionClientNode: Periodically calls the service every 500ms

Services

  • Service Server: /add_two_ints

    • Type: example_interfaces/srv/AddTwoInts

    • Description: Adds two integers and returns the sum

  • Service Client: /add_two_ints

    • Type: example_interfaces/srv/AddTwoInts

    • Description: Calls the add_two_ints service every 500ms

Parameters

  • client_configure_introspection (string, default: “disabled”): Controls client introspection

    • Valid values: “disabled”, “metadata”, “contents”

  • service_configure_introspection (string, default: “disabled”): Controls service introspection

    • Valid values: “disabled”, “metadata”, “contents”

Example Usage

# Run with introspection disabled (default)
ros2 run demo_nodes_py introspection

# Run with both client and service introspection enabled (metadata mode)
ros2 run demo_nodes_py introspection \
    --ros-args \
    -p client_configure_introspection:=metadata \
    -p service_configure_introspection:=metadata

# Run with contents introspection
ros2 run demo_nodes_py introspection \
    --ros-args \
    -p client_configure_introspection:=contents \
    -p service_configure_introspection:=contents

To dynamically enable introspection at runtime:

# Terminal 1: Run the node
ros2 run demo_nodes_py introspection

# Terminal 2: Enable client introspection
ros2 param set /introspection_client client_configure_introspection metadata

# Terminal 3: Monitor service events
ros2 topic echo /add_two_ints/_service_event

Expected output:

[INFO] [introspection_client]: Result of add_two_ints: 5
[INFO] [introspection_service]: Incoming request
a: 2 b: 3