/*
Parse a gilmour *Message and for subscribers of this topic do the following:
* If subscriber is one shot, unsubscribe the subscriber to prevent subscribers from re-execution.
* If subscriber belongs to a group, try acquiring a lock via backend to ensure group exclusivity.
* If all conditions suffice spin up a new goroutine for each subscription.
*/
func (g *Gilmour) processMessage(msg *proto.Packet) {
subs, ok := g.getSubscribers(msg.GetPattern())
if !ok || len(subs) == 0 {
ui.Warn("*Message cannot be processed. No subs found for key %v", msg.GetPattern())
return
}
m, err := parseMessage(msg.GetData())
if err != nil {
ui.Alert(err.Error())
return
}
for _, s := range subs {
opts := s.GetOpts()
if opts != nil && opts.isOneShot() {
ui.Message("Unsubscribing one shot response topic %v", msg.GetTopic())
go g.UnsubscribeReply(msg.GetPattern(), s)
}
if opts.GetGroup() != "" && opts.shouldSendResponse() {
if !g.backend.AcquireGroupLock(opts.GetGroup(), m.GetSender()) {
ui.Warn(
"Unable to acquire Lock. Topic %v Group %v Sender %v",
msg.GetTopic(), opts.GetGroup(), m.GetSender(),
)
continue
}
}
go g.handleRequest(s, msg.GetTopic(), m)
}
}
func (g *Gilmour) sendTimeout(senderId, channel string) {
msg := g.timeoutMessage(senderId)
if err := g.publish(channel, msg); err != nil {
ui.Alert(err.Error())
}
}
func (g *Gilmour) handleRequest(s *Subscription, topic string, m *Message) {
senderId := m.GetSender()
req := &Request{topic, m}
res := NewMessage()
res.setSender(proto.ResponseTopic(senderId))
done := make(chan bool, 1)
//Executing Request
go func(done chan<- bool) {
// Schedule a function to recover in case handler runs into an error.
// Read more: https://gist.github.com/meson10/d56eface6f87c664d07d
defer func() {
err := recover()
if err == nil {
return
}
const size = 4096
buf := make([]byte, size)
buf = buf[:runtime.Stack(buf, false)]
buffer := string(buf)
res.SetData(buffer).SetCode(500)
done <- true
}()
s.GetHandler()(req, res)
done <- true
}(done)
// Start a timeout handler, which writes on the Done channel, ahead of the
// handler. This might result in a RACE condition, as there is no way to
// kill a goroutine, since they are not preemptive.
timeout := s.GetOpts().GetTimeout()
time.AfterFunc(time.Duration(timeout)*time.Second, func() {
done <- false
})
status := <-done
if s.GetOpts().shouldSendResponse() {
if status == false {
g.sendTimeout(senderId, res.GetSender())
} else {
if res.GetCode() == 0 {
res.SetCode(200)
}
if err := g.publish(res.GetSender(), res); err != nil {
ui.Alert(err.Error())
}
}
} else if status == false {
// Inform the error catcher, If there is no handler for this Request
// but the request had failed. This is automatically handled in case
// of a response being written via Publisher.
request := string(req.bytes())
errMsg := proto.MakeError(499, topic, request, "", req.Sender(), "")
g.reportError(errMsg)
}
}