Hi,

I start to use lifecycle feature of ROS2. I have a confusion and please help me to clarify it.

The ROS 2 Design Page says,

Lifecycle events

A topic should be provided to broadcast the new life cycle state when it changes. This topic must be latched. The topic must be named lifecycle_state it will carry both the end state and the transition, with result code. It will publish every time that a transition is triggered, whether successful or not.

However, no topic named 'lifecycle_state' is published in demos of lifecyle and I couldn't find any other example which publish such topic. Which can I rely on, design or implementation?

Of course insted of such topic, we can use 'getstate' service and 'transisionevent' topic to know the state transitions. But 'transition_event' topic is not latched, so we have to use the service to know the node state at first time. I feel the latched topic is more handy to know the transtion and current state as in the design document. Could you point me where any discussion on it?

Thanks,