let onNeighborUp (state: State) peer = async { return { state with EagerPushPeers = Set.add peer state.EagerPushPeers } } let onNeighborDown (state: State) peer = async { return { state with // Remove notifications about messages missing from given peer Missing = state.Missing |> Set.filter (fun m -> m.Sender = peer) // Eager & lazy peers need an active connection.