Open
Description
A number of transport actions are used cross clusters. Today it is challenging to migrate any of them to use a different action because there is no way to determine when we can safely use the new action. For example, RemoteClusterService#collectNodes uses GetClusterState action to retrieve all nodes of remote clusters. But this is both not efficient (because ClusterState could be heavy) and not accurate (because this method is used in scroll search context and only needs nodes related to the scrolls). We’d like to change it to use a different action to improve on both of the issues. But this requires a way to determine when to use the new or the old action and handle BWC accordingly.
Relates: #89456