The BondClient class manages the lifecycle of a bond between the Fabric node and the capabilities server. Bonds are used to monitor the connection and ensure both sides are alive and responsive during plan execution.

Purpose

Establishes a heartbeat connection (bond) with the capabilities server for a specific plan execution (identified by a bond ID).
Monitors the bond state to detect if the connection is formed or broken.
Cleans up the bond when execution is complete or the client is destroyed.

Main Methods

Method	Purpose
`BondClient(node, bond_id)`	Constructor. Initializes the bond client with the node and bond ID. Retrieves the bond topic from parameters.
`start()`	Starts the bond, sets heartbeat period and timeout, and logs the event.
`stop()`	Stops and cleans up the bond, logging the event.
`~BondClient()`	Destructor. Ensures the bond is stopped and cleaned up.

Callbacks

on_formed(): Called when the bond is successfully established. Logs the event.
on_broken(): Called when the bond is broken (e.g., server disconnects or crashes). Logs the event.

Usage in Fabric

Each plan execution is associated with a unique bond ID.
The Fabric server creates a BondClient for each new plan, starts the bond, and monitors its state.
When the plan is complete or needs to be stopped, the bond is stopped and cleaned up.
If the bond is broken unexpectedly, the system can take recovery actions or log the failure.

Parameters

capability_client.bond_topic: The ROS parameter specifying the bond topic (default: /capabilities/bond).

Runtime Behavior

start() creates a bond::Bond, sets a 0.10 s heartbeat period, sets a 10.0 s timeout, and starts the heartbeat.
stop() destroys the bond client instance if one exists.

Example Flow

Initialization: BondClient is constructed with the node and bond ID.
Start: start() is called to begin the bond heartbeat.
Monitor: The bond state is monitored via on_formed() and on_broken() callbacks.
Stop: stop() is called when the plan is done or the client is destroyed.

The BondClient ensures robust monitoring of the connection between Fabric and the capabilities server, enabling reliable plan execution and graceful handling of disconnections or failures.