The fact that it takes so long for a node to go away might be related to the Fast-RTPS settings or perhaps if the node is not terminated cleanly.
@karsten implemented this, so I’ll let him chime in, but we might need to change the implementation of this anyways to address node name uniqueness or the mapping of nodes to participants.
We have the graph API for changes to the graph, but I think it currently does not get notified when new nodes are added or when nodes are removed. I guess @karsten just didn’t implement that part when doing the initial implementation. Again the behavior (or underlying mechanism) may need to change in the future.