PeerSelection: perhaps extract logic to select peers as a protocol #496
Description
We could do
/// Peer Selection is a common step in various gossip protocols.
///
/// Selecting a peer may be as trivial as randomly selecting one among known actors or nodes,
/// round-robin cycling through peers or a mix thereof in which the order is randomized _but stable_
/// which reduces the risk of gossiping to the same or starving certain peers in situations when many
/// new peers are added to the group.
///
/// // TODO: implement SWIMs selection in terms of this
public protocol PeerSelection {
associatedtype Peer: Hashable
public typealias Peers = [Peer]
associatedtype Payload: Equatable
func onMembershipEvent(event: Cluster.Event)
func select(for payload: Payload?) -> Peers
}if we want to reuse it among other impls.
E.g. SWIM has a pretty good strategy and it might be good to use for our other gossips as well.