i found rpc:call from erlang to ergo is not work

[xiaodoudou12]

my OTP version is Erlang/OTP 24 [erts-12.1.5] [source] [64-bit] [smp:4:4] [ds:4:4:10] [async-threads:1] [jit].
golang version is go1.18.ergo version is v1.999.211.
i use https://github.com/ergo-services/ergo/blob/v1.999.211/examples/genserver/server.go this to test.
gen_server:cast and gen_server:call is ok,but rpc:call failed.
https://github.com/ergo-services/ergo/blob/v1.999.211/proto/dist/proto.go in this file

			case distProtoSPAWN_REQUEST:
				// {29, ReqId, From, GroupLeader, {Module, Function, Arity}, OptList}
				lib.Log("[%s] CONTROL SPAWN_REQUEST [from %s]: %#v", dc.nodename, dc.peername, message.control)
				if message.proxy != nil && message.proxy.session.NodeFlags.EnableRemoteSpawn == false {
					// we didn't allow this feature. proxy session will be closed due to
					// this violation of the contract
					return node.ErrPeerUnsupported
				}
				registerName := ""
				for _, option := range t.Element(6).(etf.List) {
					name, ok := option.(etf.Tuple)
					if !ok || len(name) != 2 {
						return fmt.Errorf("malformed spawn request")
					}
					switch name.Element(1) {
					case etf.Atom("name"):
						registerName = string(name.Element(2).(etf.Atom))
					}
				}

				from := t.Element(3).(etf.Pid)
				ref := t.Element(2).(etf.Ref)

				mfa := t.Element(5).(etf.Tuple)
				module := mfa.Element(1).(etf.Atom)
				function := mfa.Element(2).(etf.Atom)
				var args etf.List
				if str, ok := message.payload.(string); !ok {
					args, _ = message.payload.(etf.List)
				} else {
					// stupid Erlang's strings :). [1,2,3,4,5] sends as a string.
					// args can't be anything but etf.List.
					for i := range []byte(str) {
						args = append(args, str[i])
					}
				}

the message value is

&dist.distMessage{
control:etf.Tuple{29, etf.Ref{Node:"[email protected]", Creation:0x636ca74d, ID:[5]uint32{0x143cd, 0x843c0001, 0x9a32d1ab, 0x0, 0x0}}, etf.Pid{Node:"[email protected]", ID:0x55, Creation:0x636ca74d}, etf.Pid{Node:"[email protected]", ID:0x47, Creation:0x636ca74d}, etf.Tuple{"erpc", "execute_call", 4}, etf.List{"monitor"}}, payload:etf.List{etf.Ref{Node:"[email protected]", Creation:0x636ca74d, ID:[5]uint32{0x143cb, 0x843c0001, 0x9a32d1ab, 0x0, 0x0}}, "rpc", "request", etf.List{"hello", 3.14}}, proxy:(*dist.proxySession)(nil)}

t.Element(6). is etf.List{"monitor"}, and len(name) != 2, so it failed
i found registerName should be erpc, i don't know is conrrect.

and node/core.go in function func (c *core) RouteSpawnRequest

		// spawn new process
		process_opts := processOptions{}
		process_opts.Env = map[gen.EnvKey]interface{}{EnvKeyRemoteSpawn: request.Options}
		process, err_spawn := c.spawn(request.Options.Name, process_opts, b.Behavior, args...)

process_opts.Env show init add "ergo:RemoteSpawnRequest" like this

process_opts.Env = map[gen.EnvKey]interface{}{EnvKeyRemoteSpawn: request.Options, "ergo:RemoteSpawnRequest":request}

because in erlang/rex.go in func (e *erpc) HandleCast will need process.Env("ergo:RemoteSpawnRequest")

func (e *erpc) HandleCast(process *gen.ServerProcess, message etf.Term) gen.ServerStatus {
	lib.Log("ERPC [%v]: HandleCast: %#v", process.Self(), message)
	mfa := message.(erpcMFA)
	rsr := process.Env("ergo:RemoteSpawnRequest").(gen.RemoteSpawnRequest)

so that,rpc:call from erlang to ergo work ok,but rpc:cast not work also.

in erlang i use like this
([email protected])1> rpc:call('[email protected]', rpc, request, [hello, 3.14]).
[hello,3.14]

[halturin]

Its a bug. Created new issue #116

[halturin]

anyway, I wouldn't recommend using this feature in production since it has very limited performance (in erlang, too).

[xiaodoudou12]

in the examples/erlang/server.go, erlang to ergo node work ok,but in my other question, ergo to erlang sometimes work ok,and sometimes work failed,
is also better use ServerProcess:Cast and ServerProcess:Call in golang to send message to erlang.but what is to interface{} i should set

[halturin]

to could be:

• etf.Pid
• etf.Atom("process_name") or just a string "process_name" - for local messaging only
• gen.ProcessID{Name: "process_name", Node: "[email protected]"}

and yes, that's correct - to send a cast message, you should use ServerProcess:Cast(...), and to make a call request - ServerProcess:Call(..). You may also use Process.Send(..) (or ServerProcess:Send(..) which is inherited from Process) to send a regular message in fashion of erlang:send(..)

[xiaodoudou12]

oh, thank you, i will try it.

[xiaodoudou12]

i try it finish.it work like RPCCall and RPCCast, sometimes is ok, sometimes failed.
i use like this

to := gen.ProcessID{Name: "ergo_msg_itf", Node: "[email protected]"}
args :=  []etf.Term{"ch", 1}
process.Send(to, args)

Handshake error: malformed handshake ('a' length of digest) show when failed.

[halturin]

I guess I know the problem. I'll take a look at this a bit later.