multicall(Nodes, M, F, A, RecvTO, SendTO)
rpc multicall requires that the call be sent concurrently to all nodes & failure on individual node won't affect requests to other nodes.
use async to establish peer gen_rpc_server process and execute M,F,A on each node, so won't block
gather results from nb_yield to filter for Results and Badnodes
If Nodes is [], returns both Results and BadNodes are []
Implementation of
This PR uses async and yield so is related to https://github.com/priestjim/gen_rpc/pull/27