//export ListenAndServe
func ListenAndServe(addr_ C.SEXP, handler_ C.SEXP, rho_ C.SEXP) C.SEXP {
if C.TYPEOF(addr_) != C.STRSXP {
fmt.Printf("addr is not a string (STRXSP; instead it is: %d)! addr argument to ListenAndServe() must be a string of form 'ip:port'\n", C.TYPEOF(addr_))
return C.R_NilValue
}
//msglen := 0
if 0 == int(C.isFunction(handler_)) { // 0 is false
C.ReportErrorToR_NoReturn(C.CString("‘handler’ must be a function"))
return C.R_NilValue
}
if rho_ != nil && rho_ != C.R_NilValue {
if 0 == int(C.isEnvironment(rho_)) { // 0 is false
C.ReportErrorToR_NoReturn(C.CString("‘rho’ should be an environment"))
return C.R_NilValue
}
}
caddr := C.R_CHAR(C.STRING_ELT(addr_, 0))
addr := C.GoString(caddr)
fmt.Printf("ListenAndServe listening on address '%s'...\n", addr)
webSockHandler := func(w http.ResponseWriter, r *http.Request) {
if r.URL.Path != "/" {
http.Error(w, "Not found", 404)
return
}
if r.Method != "GET" {
http.Error(w, "Method not allowed, only GET allowed.", 405)
return
}
c, err := upgrader.Upgrade(w, r, nil)
if err != nil {
fmt.Print("websocket handler upgrade error:", err)
return
}
defer c.Close()
mt, message, err := c.ReadMessage()
if err != nil {
fmt.Println("read error: ", err)
return
}
// make the call, and get a response
msglen := len(message)
rawmsg := C.allocVector(C.RAWSXP, C.R_xlen_t(msglen))
C.Rf_protect(rawmsg)
C.memcpy(unsafe.Pointer(C.RAW(rawmsg)), unsafe.Pointer(&message[0]), C.size_t(msglen))
// put msg into env that handler_ is called with.
C.defineVar(C.install(C.CString("msg")), rawmsg, rho_)
R_serialize_fun = C.findVar(C.install(C.CString("serialize")), C.R_GlobalEnv)
// todo: callbacks to R functions here not working. don't really need them if R always acts as a client instead.
// evaluate
C.PrintToR(C.CString("listenAndServe: stuffed msg into env rho_.\n"))
//R_fcall := C.lang3(handler_, rawmsg, C.R_NilValue)
R_fcall := C.lang3(R_serialize_fun, rawmsg, C.R_NilValue)
C.Rf_protect(R_fcall)
C.PrintToR(C.CString("listenAndServe: got msg, just prior to eval.\n"))
evalres := C.eval(R_fcall, rho_)
C.Rf_protect(evalres)
C.PrintToR(C.CString("listenAndServe: after eval.\n"))
/*
var s, t C.SEXP
s = C.allocList(3)
t = s
C.Rf_protect(t)
C.SetTypeToLANGSXP(&s)
//C.SETCAR(t, R_fcall)
C.SETCAR(t, handler_)
t = C.CDR(t)
C.SETCAR(t, rawmsg)
evalres := C.eval(s, rho_)
C.Rf_protect(evalres)
*/
C.PrintToR(C.CString("nnListenAndServe: done with eval.\n"))
if C.TYPEOF(evalres) != C.RAWSXP {
fmt.Printf("rats! handler result was not RAWSXP raw bytes!\n")
} else {
//fmt.Printf("recv: %s\n", message)
err = c.WriteMessage(mt, message)
if err != nil {
fmt.Println("write error: ", err)
}
}
C.Rf_unprotect(3)
} // end handler func
http.HandleFunc("/", webSockHandler)
err := http.ListenAndServe(addr, nil)
if err != nil {
fmt.Println("ListenAndServe: ", err)
}
return C.R_NilValue
}
//export ListenAndServe
//
// ListenAndServe is the server part that expects calls from client
// in the form of RmqWebsocketCall() invocations.
// The underlying websocket library is the battle tested
// https://github.com/gorilla/websocket library from the
// Gorilla Web toolkit. http://www.gorillatoolkit.org/
//
// addr_ is a string in "ip:port" format. The server
// will bind this address and port on the local host.
//
// handler_ is an R function that takes a single argument.
// It will be called back each time the server receives
// an incoming message. The returned value of handler
// becomes the reply to the client.
//
// rho_ is an R environment in which the handler_ callback
// will occur. The user-level wrapper rmq.server() provides
// a new environment for every call back by default, so
// most users won't need to worry about rho_.
//
// Return value: this is always R_NilValue.
//
// Semantics: ListenAndServe() will start a new
// webserver everytime it is called. If it exits
// due to a call into R_CheckUserInterrupt()
// or Rf_error(), then a background watchdog goroutine
// will notice the lack of heartbeating after 300ms,
// and will immediately shutdown the listening
// websocket server goroutine. Hence cleanup
// is fairly automatic.
//
// Signal handling:
//
// SIGINT (ctrl-c) is noted by R, and since we
// regularly call R_CheckUserInterrupt(), the
// user can stop the server by pressing ctrl-c
// at the R-console. The go-runtime, as embedded
// in the c-shared library, is not accustomed to being
// embedded yet, and so its (system) signal handling
// facilities (e.g. signal.Notify) should *not* be
// used. We go to great pains to actually preserve
// the signal handling that R sets up and expects,
// as allowing the go runtime to see any signals just
// creates heartache and crashes.
//
func ListenAndServe(addr_ C.SEXP, handler_ C.SEXP, rho_ C.SEXP) C.SEXP {
addr, err := getAddr(addr_)
if err != nil {
C.ReportErrorToR_NoReturn(C.CString(err.Error()))
return C.R_NilValue
}
if 0 == int(C.isFunction(handler_)) { // 0 is false
C.ReportErrorToR_NoReturn(C.CString("‘handler’ must be a function"))
return C.R_NilValue
}
if rho_ != nil && rho_ != C.R_NilValue {
if 0 == int(C.isEnvironment(rho_)) { // 0 is false
C.ReportErrorToR_NoReturn(C.CString("‘rho’ should be an environment"))
return C.R_NilValue
}
}
fmt.Printf("ListenAndServe listening on address '%s'...\n", addr)
// Motivation: One problem when acting as a web server is that
// webSockHandler will be run on a separate goroutine and this will surely
// be a separate thread--distinct from the R callback thread. This is a
// problem because if we call back into R from the goroutine thread
// instead of R's thread, R will see the small stack and freak out.
//
// So: we'll use a channel to send the request to the main R thread
// for call back into R. The *[]byte passed on these channels represent
// msgpack serialized R objects.
requestToRCh := make(chan *[]byte)
replyFromRCh := make(chan *[]byte)
reqStopCh := make(chan bool)
doneCh := make(chan bool)
var lastControlHeartbeatTimeNano int64
beatHeart := func() {
now := int64(time.Now().UnixNano())
atomic.StoreInt64(&lastControlHeartbeatTimeNano, now)
}
webSockHandler := func(w http.ResponseWriter, r *http.Request) {
if r.URL.Path != "/" {
http.Error(w, "Not found", 404)
return
}
if r.Method != "GET" {
http.Error(w, "Method not allowed, only GET allowed.", 405)
return
}
c, err := upgrader.Upgrade(w, r, nil)
if err != nil {
msg := fmt.Sprintf("server webSockHandler() handler saw "+
"websocket upgrader.Upgrade() error: '%s'", err)
fmt.Printf("%s\n", msg)
http.Error(w, msg, 500)
return
}
defer c.Close()
_, message, err := c.ReadMessage()
if err != nil {
msg := fmt.Sprintf("server webSockHandler() handler saw "+
"websocket ReadMessage() error: '%s'", err)
fmt.Printf("%s\n", msg)
http.Error(w, msg, 500)
return
}
requestToRCh <- &message
reply := <-replyFromRCh
err = c.WriteMessage(websocket.BinaryMessage, *reply)
if err != nil {
msg := fmt.Sprintf("server webSockHandler() handler saw "+
"websocket WriteMessage() error: '%s'", err)
fmt.Printf("%s\n", msg)
http.Error(w, msg, 500)
return
}
} // end webSockHandler
// start a new server, to avoid registration issues with
// the default http library mux/server which may be in use
// already for other purposes.
mux := http.NewServeMux()
mux.HandleFunc("/", webSockHandler)
server := NewWebServer(addr.String(), mux)
server.Start()
// This watchdog will shut the webserver down
// if lastControlHeartbeatTimeNano goes
// too long without an update. This will
// happen when C.R_CheckUserInterrupt()
// doesn't return below in the main control loop.
beatHeart()
go func() {
for {
select {
case <-time.After(time.Millisecond * 100):
last := atomic.LoadInt64(&lastControlHeartbeatTimeNano)
lastTm := time.Unix(0, last)
deadline := lastTm.Add(300 * time.Millisecond)
now := time.Now()
if now.After(deadline) {
VPrintf("\n web-server watchdog: no heartbeat "+
"after %v, shutting down.\n", now.Sub(lastTm))
server.Stop()
return
}
}
}
}()
// This is the main control routine that lives on the main R thread.
// All callbacks into R must come from this thread, as it is a
// C thread with a big stack. Go routines have tiny stacks and
// R detects this and crashes if you try to call back from one of them.
for {
select {
case <-time.After(time.Millisecond * 100):
//
// Our heartbeat logic:
//
// R_CheckUserInterrupt() will check if Ctrl-C
// was pressed by user and R would like us to stop.
// (R's SIGINT signal handler is installed in our
// package init() routine at the top of this file.)
//
// Note that R_CheckUserInterrupt() may not return!
// So, Q: how will the server know to cancel/cleanup?
// A: we'll have the other goroutines check the following
// timestamp. If it is too out of date, then they'll
// know that they should cleanup.
beatHeart()
C.R_CheckUserInterrupt()
case msgpackRequest := <-requestToRCh:
rRequest := decodeMsgpackToR(*msgpackRequest)
C.Rf_protect(rRequest)
// Call into the R handler_ function, and get its reply.
R_fcall := C.lang2(handler_, rRequest)
C.Rf_protect(R_fcall)
if Verbose {
C.PrintToR(C.CString("listenAndServe: got msg, just prior to eval.\n"))
}
evalres := C.eval(R_fcall, rho_)
C.Rf_protect(evalres)
if Verbose {
C.PrintToR(C.CString("listenAndServe: after eval.\n"))
}
// send back the reply, first converting to msgpack
reply := encodeRIntoMsgpack(evalres)
C.Rf_unprotect(3)
replyFromRCh <- &reply
case <-reqStopCh:
// not sure who should close(reqStopCh). At the moment it isn't used.
close(doneCh)
return C.R_NilValue
}
}
}