# lifecycle_talker

*This file is ai generated. Do not edit this file directly. Instead, edit the node source code and run the generate-node-docs command to update this file.*

## Description

A demonstration lifecycle node that publishes string messages to illustrate ROS 2 lifecycle management in Python. The node implements the managed lifecycle pattern, transitioning through various states (unconfigured, inactive, active, finalized) and only publishing messages when in the active state.

## Publishers

- **`lifecycle_chatter`** ([example_interfaces/msg/String](https://github.com/ros2/example_interfaces/blob/rolling/msg/String.msg))
  - Lifecycle-managed publisher that sends sequential "Lifecycle HelloWorld" messages with an incrementing counter
  - Only publishes when the node is in the active state
  - Publishing rate: 1 Hz

## Services

As a lifecycle node, this node automatically provides the following lifecycle management services:

- **`~/change_state`** ([lifecycle_msgs/srv/ChangeState](https://github.com/ros2/rcl_interfaces/blob/rolling/lifecycle_msgs/srv/ChangeState.srv))
  - Requests a state transition for the lifecycle node
  
- **`~/get_state`** ([lifecycle_msgs/srv/GetState](https://github.com/ros2/rcl_interfaces/blob/rolling/lifecycle_msgs/srv/GetState.srv))
  - Retrieves the current state of the lifecycle node
  
- **`~/get_available_states`** ([lifecycle_msgs/srv/GetAvailableStates](https://github.com/ros2/rcl_interfaces/blob/rolling/lifecycle_msgs/srv/GetAvailableStates.srv))
  - Lists all possible states the lifecycle node can be in
  
- **`~/get_available_transitions`** ([lifecycle_msgs/srv/GetAvailableTransitions](https://github.com/ros2/rcl_interfaces/blob/rolling/lifecycle_msgs/srv/GetAvailableTransitions.srv))
  - Lists all available state transitions from the current state
  
- **`~/get_transition_graph`** ([lifecycle_msgs/srv/GetAvailableTransitions](https://github.com/ros2/rcl_interfaces/blob/rolling/lifecycle_msgs/srv/GetAvailableTransitions.srv))
  - Retrieves the complete state transition graph

## Lifecycle States and Transitions

### Primary States

1. **Unconfigured** - Initial state after node creation
2. **Inactive** - Configured but not yet active
3. **Active** - Fully operational, publishing messages
4. **Finalized** - Terminal state after shutdown

### State Transitions

The node implements the following lifecycle callbacks:

- **`on_configure()`** - Called during transition from unconfigured → inactive
  - Creates the lifecycle publisher on topic `lifecycle_chatter`
  - Creates a 1 Hz timer for publishing messages
  - Returns `SUCCESS` to complete transition to inactive state

- **`on_activate()`** - Called during transition from inactive → active
  - Enables the lifecycle publisher (handled automatically by parent class)
  - Logs activation event
  - Returns `SUCCESS` to complete transition to active state

- **`on_deactivate()`** - Called during transition from active → inactive
  - Disables the lifecycle publisher (handled automatically by parent class)
  - Logs deactivation event
  - Returns `SUCCESS` to complete transition to inactive state

- **`on_cleanup()`** - Called during transition from inactive → unconfigured
  - Destroys the timer
  - Destroys the publisher
  - Returns `SUCCESS` to complete transition to unconfigured state

- **`on_shutdown()`** - Called during transition to finalized state
  - Cleans up timer and publisher resources
  - Can be called from any state
  - Returns `SUCCESS` to complete transition to finalized state

### Transition Commands

The node can be controlled using the lifecycle service client or CLI:

```bash
# Get current state
ros2 lifecycle get /lc_talker

# Configure the node
ros2 lifecycle set /lc_talker configure

# Activate the node
ros2 lifecycle set /lc_talker activate

# Deactivate the node
ros2 lifecycle set /lc_talker deactivate

# Cleanup (go back to unconfigured)
ros2 lifecycle set /lc_talker cleanup

# Shutdown the node
ros2 lifecycle set /lc_talker shutdown
```

## Example Usage

### Running the Node Directly

Start the lifecycle talker node:

```bash
ros2 run lifecycle_py lifecycle_talker
```

The node starts in the **unconfigured** state and will not publish messages until activated.

### Controlling the Node Lifecycle

In separate terminals, control the lifecycle:

```bash
# Terminal 1: Run the node
ros2 run lifecycle_py lifecycle_talker

# Terminal 2: Configure the node
ros2 lifecycle set /lc_talker configure

# Terminal 3: Activate the node (starts publishing)
ros2 lifecycle set /lc_talker activate

# Terminal 4: Monitor the messages
ros2 topic echo /lifecycle_chatter
```

### Using the Launch File

Launch the complete lifecycle demo with talker, listener, and service client:

```bash
ros2 launch lifecycle_py lifecycle_demo_launch.py
```

This launch file starts:
- The lifecycle talker node
- A lifecycle listener node (from the lifecycle package)
- A lifecycle service client (from the lifecycle package) for automated state transitions

### Example Output

When inactive:
```
[INFO] [lc_talker]: Lifecycle publisher is inactive. Messages are not published.
```

When active:
```
[INFO] [lc_talker]: Lifecycle publisher is active. Publishing: [Lifecycle HelloWorld #0]
[INFO] [lc_talker]: Lifecycle publisher is active. Publishing: [Lifecycle HelloWorld #1]
[INFO] [lc_talker]: Lifecycle publisher is active. Publishing: [Lifecycle HelloWorld #2]
```

### Programmatic State Transitions

You can also interact with the lifecycle services programmatically:

```python
from lifecycle_msgs.srv import ChangeState, GetState
from lifecycle_msgs.msg import Transition
import rclpy

# Get current state
get_state_client = node.create_client(GetState, '/lc_talker/get_state')
request = GetState.Request()
future = get_state_client.call_async(request)

# Change state to configure
change_state_client = node.create_client(ChangeState, '/lc_talker/change_state')
request = ChangeState.Request()
request.transition.id = Transition.TRANSITION_CONFIGURE
future = change_state_client.call_async(request)

# Change state to activate
request.transition.id = Transition.TRANSITION_ACTIVATE
future = change_state_client.call_async(request)
```