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Configure action introspection

Goal: Configure action introspection for an action client and an action server.

Tutorial level: Advanced

Time: 15 minutes

Overview 

ROS 2 applications usually consist of actions to execute specific long-running procedures or work in remote nodes. It is possible to introspect action data communication with action introspection.

ROS 2 actions are built on topics and services, so action introspection is based on Service Introspection.

In this demo, we’ll be highlighting how to configure action introspection state for an action client and an action server and monitor action communication with ros2 action echo.

Installing the demo 

See the installation instructions for details on installing ROS 2.

If you’ve installed ROS 2 binary packages, ensure that you have ros-rolling-demo-nodes-cpp and ros-rolling-demo-nodes-py installed. If you downloaded the archive or built ROS 2 from source, it will already be part of the installation.

Introspection Configuration State 

There are three configuration states for action introspection that are the same states as service introspection.

Action Introspection Configuration State
RCL_SERVICE_INTROSPECTION_OFF	Disabled
RCL_SERVICE_INTROSPECTION_METADATA	Only metadata without any user data contents
RCL_SERVICE_INTROSPECTION_CONTENTS	User data contents with metadata

Introspection demo 

This demo shows how to manage action introspection and monitor the action data communication with using ros2 action echo.

Action server

You can find the source code here: fibonacci_action_server.py. FibonacciActionServer has a parameter named action_server_configure_introspection to configure the action introspection state.

class FibonacciActionServer(Node):
...
    def on_post_set_parameters_callback(self, parameter_list):
        for param in parameter_list:
            if param.name != 'action_server_configure_introspection':
                continue

            introspection_state = ServiceIntrospectionState.OFF
            if param.value == 'disabled':
                introspection_state = ServiceIntrospectionState.OFF
            elif param.value == 'metadata':
                introspection_state = ServiceIntrospectionState.METADATA
            elif param.value == 'contents':
                introspection_state = ServiceIntrospectionState.CONTENTS

            self._action_server.configure_introspection(self.get_clock(),
                                                        qos_profile_system_default,
                                                        introspection_state)
            break
...

If you want to try the C++ version, you can find the source code here: fibonacci_action_server.cpp.

Action introspection is disabled by default, so users need to enable it with action_server_configure_introspection parameter when the server starts up. In this demo, FibonacciActionServer enables action introspection when the value of the action_server_configure_introspection parameter is contents.

ros2 run action_tutorials_py fibonacci_action_server --ros-args -p action_server_configure_introspection:=contents

To change action introspection state, we need to set the action_server_configure_introspection parameter as follows.

### User data contents with metadata
$ ros2 param set /fibonacci_action_server action_server_configure_introspection contents
### Or only metadata
$ ros2 param set /fibonacci_action_server action_server_configure_introspection metadata
### To disable
$ ros2 param set /fibonacci_action_server action_server_configure_introspection disabled

Action client

You can find the source code here: fibonacci_action_client.cpp. FibonacciActionClient has a parameter named action_client_configure_introspection to configure the action introspection state.

namespace action_tutorials_cpp
{
class FibonacciActionClient : public rclcpp::Node
...
    auto post_set_parameter_callback =
      [this](const std::vector<rclcpp::Parameter> & parameters) {
        for (const rclcpp::Parameter & param : parameters) {
          if (param.get_name() != "action_client_configure_introspection") {
            continue;
          }

          rcl_service_introspection_state_t introspection_state = RCL_SERVICE_INTROSPECTION_OFF;

          if (param.as_string() == "disabled") {
            introspection_state = RCL_SERVICE_INTROSPECTION_OFF;
          } else if (param.as_string() == "metadata") {
            introspection_state = RCL_SERVICE_INTROSPECTION_METADATA;
          } else if (param.as_string() == "contents") {
            introspection_state = RCL_SERVICE_INTROSPECTION_CONTENTS;
          }

          this->client_ptr_->configure_introspection(
            this->get_clock(), rclcpp::SystemDefaultsQoS(), introspection_state);
          break;
        }
      };
...

If you want to try the Python version, you can find the source code here: fibonacci_action_client.py.

And then, we start and configure FibonacciActionClient in the same way.

ros2 run action_tutorials_cpp fibonacci_action_client --ros-args -p action_client_configure_introspection:=contents

To change action introspection state, we need to set the action_client_configure_introspection parameter as follows. Note that FibonacciActionClient only runs in short time, so it is recommended to set the parameter before running the client as above.

### User data contents with metadata
$ ros2 param set /fibonacci_action_client action_client_configure_introspection contents
### Or only metadata
$ ros2 param set /fibonacci_action_client action_client_configure_introspection metadata
### To disable
$ ros2 param set /fibonacci_action_client action_client_configure_introspection disabled

Introspect

In this tutorial, the following is an example output with action introspection state contents on both FibonacciActionServer and FibonacciActionClient. To monitor action communication between FibonacciActionServer and FibonacciActionClient, let’s run it:

$ ros2 action echo /fibonacci example_interfaces/action/Fibonacci --flow-style
interface: GOAL_SERVICE
info:
  event_type: REQUEST_SENT
  stamp:
    sec: 1742070798
    nanosec: 400435819
  client_gid: [1, 15, 165, 231, 194, 197, 167, 157, 0, 0, 0, 0, 0, 0, 20, 4]
  sequence_number: 1
request: [{goal_id: {uuid: [230, 96, 12, 6, 100, 69, 69, 70, 220, 205, 135, 251, 210, 2, 231, 110]}, goal: {order: 10}}]
response: []
---
interface: GOAL_SERVICE
info:
  event_type: REQUEST_RECEIVED
  stamp:
    sec: 1742070798
    nanosec: 400706446
  client_gid: [1, 15, 165, 231, 194, 197, 167, 157, 0, 0, 0, 0, 0, 0, 20, 4]
  sequence_number: 1
request: [{goal_id: {uuid: [230, 96, 12, 6, 100, 69, 69, 70, 220, 205, 135, 251, 210, 2, 231, 110]}, goal: {order: 10}}]
response: []
---
interface: RESULT_SERVICE
info:
  event_type: REQUEST_SENT
  stamp:
    sec: 1742070798
    nanosec: 401486678
  client_gid: [1, 15, 165, 231, 194, 197, 167, 157, 0, 0, 0, 0, 0, 0, 24, 4]
  sequence_number: 1
request: [{goal_id: {uuid: [230, 96, 12, 6, 100, 69, 69, 70, 220, 205, 135, 251, 210, 2, 231, 110]}}]
response: []
---
interface: FEEDBACK_TOPIC
goal_id:
  uuid: [230, 96, 12, 6, 100, 69, 69, 70, 220, 205, 135, 251, 210, 2, 231, 110]
feedback:
  sequence: [0, 1, 1]
---
interface: STATUS_TOPIC
status_list: [{goal_info: {goal_id: {uuid: [230, 96, 12, 6, 100, 69, 69, 70, 220, 205, 135, 251, 210, 2, 231, 110]}, stamp: {sec: 1742070798, nanosec: 401146752}}, status: 2}]
---
interface: GOAL_SERVICE
info:
  event_type: RESPONSE_SENT
  stamp:
    sec: 1742070798
    nanosec: 401109161
  client_gid: [1, 15, 165, 231, 194, 197, 167, 157, 0, 0, 0, 0, 0, 0, 20, 4]
  sequence_number: 1
request: []
response: [{accepted: true, stamp: {sec: 0, nanosec: 0}}]
---
interface: RESULT_SERVICE
info:
  event_type: REQUEST_RECEIVED
  stamp:
    sec: 1742070798
    nanosec: 401579875
  client_gid: [1, 15, 165, 231, 194, 197, 167, 157, 0, 0, 0, 0, 0, 0, 24, 4]
  sequence_number: 1
request: [{goal_id: {uuid: [230, 96, 12, 6, 100, 69, 69, 70, 220, 205, 135, 251, 210, 2, 231, 110]}}]
response: []
---
interface: GOAL_SERVICE
info:
  event_type: RESPONSE_RECEIVED
  stamp:
    sec: 1742070798
    nanosec: 401234269
  client_gid: [1, 15, 165, 231, 194, 197, 167, 157, 0, 0, 0, 0, 0, 0, 20, 4]
  sequence_number: 1
request: []
response: [{accepted: true, stamp: {sec: 0, nanosec: 0}}]
---
interface: FEEDBACK_TOPIC
goal_id:
  uuid: [230, 96, 12, 6, 100, 69, 69, 70, 220, 205, 135, 251, 210, 2, 231, 110]
feedback:
  sequence: [0, 1, 1, 2]
---
interface: FEEDBACK_TOPIC
goal_id:
  uuid: [230, 96, 12, 6, 100, 69, 69, 70, 220, 205, 135, 251, 210, 2, 231, 110]
feedback:
  sequence: [0, 1, 1, 2, 3]
---
interface: FEEDBACK_TOPIC
goal_id:
  uuid: [230, 96, 12, 6, 100, 69, 69, 70, 220, 205, 135, 251, 210, 2, 231, 110]
feedback:
  sequence: [0, 1, 1, 2, 3, 5]
---
interface: FEEDBACK_TOPIC
goal_id:
  uuid: [230, 96, 12, 6, 100, 69, 69, 70, 220, 205, 135, 251, 210, 2, 231, 110]
feedback:
  sequence: [0, 1, 1, 2, 3, 5, 8]
---
interface: FEEDBACK_TOPIC
goal_id:
  uuid: [230, 96, 12, 6, 100, 69, 69, 70, 220, 205, 135, 251, 210, 2, 231, 110]
feedback:
  sequence: [0, 1, 1, 2, 3, 5, 8, 13]
---
interface: FEEDBACK_TOPIC
goal_id:
  uuid: [230, 96, 12, 6, 100, 69, 69, 70, 220, 205, 135, 251, 210, 2, 231, 110]
feedback:
  sequence: [0, 1, 1, 2, 3, 5, 8, 13, 21]
---
interface: FEEDBACK_TOPIC
goal_id:
  uuid: [230, 96, 12, 6, 100, 69, 69, 70, 220, 205, 135, 251, 210, 2, 231, 110]
feedback:
  sequence: [0, 1, 1, 2, 3, 5, 8, 13, 21, 34]
---
interface: FEEDBACK_TOPIC
goal_id:
  uuid: [230, 96, 12, 6, 100, 69, 69, 70, 220, 205, 135, 251, 210, 2, 231, 110]
feedback:
  sequence: [0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55]
---
interface: RESULT_SERVICE
info:
  event_type: RESPONSE_SENT
  stamp:
    sec: 1742070807
    nanosec: 402339670
  client_gid: [1, 15, 165, 231, 194, 197, 167, 157, 0, 0, 0, 0, 0, 0, 24, 4]
  sequence_number: 1
request: []
response: [{status: 4, result: {sequence: [0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55]}}]
---
interface: RESULT_SERVICE
info:
  event_type: RESPONSE_RECEIVED
  stamp:
    sec: 1742070807
    nanosec: 402698784
  client_gid: [1, 15, 165, 231, 194, 197, 167, 157, 0, 0, 0, 0, 0, 0, 24, 4]
  sequence_number: 1
request: []
response: [{status: 4, result: {sequence: [0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55]}}]
---
interface: STATUS_TOPIC
status_list: [{goal_info: {goal_id: {uuid: [230, 96, 12, 6, 100, 69, 69, 70, 220, 205, 135, 251, 210, 2, 231, 110]}, stamp: {sec: 1742070798, nanosec: 401146752}}, status: 4}]
---
...

You can see the interface: GOAL_SERVICE and interface: RESULT_SERVICE, those introspection service events take place in both FibonacciActionServer and FibonacciActionClient. And you can also see interface: FEEDBACK_TOPIC and interface: STATUS_TOPIC data, those topics are published by FibonacciActionServer and subscribed by FibonacciActionClient.

Now you can see the action communication between FibonacciActionServer and FibonacciActionClient with ros2 action echo.

Configure action introspection

Overview

Installing the demo

Introspection Configuration State

Introspection demo