// Request part of Request-Reply design pattern.
func (g *Gilmour) request(topic string, msg *Message, opts *RequestOpts) (*Response, error) {
if has, err := g.backend.HasActiveSubscribers(g.requestDestination(topic)); err != nil {
return nil, err
} else if !has {
return nil, errors.New("No active listeners for: " + topic)
}
if msg == nil {
msg = NewMessage()
}
sender := proto.SenderId()
msg.setSender(sender)
respChannel := proto.ResponseTopic(sender)
if opts == nil {
opts = NewRequestOpts()
}
//Wait for a responseHandler
f := make(chan *Message, 1)
rOpts := NewHandlerOpts().setOneShot().sendResponse(false)
g.ReplyTo(respChannel, func(req *Request, _ *Message) {
f <- req.gData
}, rOpts)
// Send Timeout message to channel, Need to send timeout over the wire,
// to ensure gilmour cleans up the oneShot response handlers as well.
timeout := opts.GetTimeout()
if timeout > 0 {
time.AfterFunc(time.Duration(timeout)*time.Second, func() {
g.sendTimeout(sender, respChannel)
})
}
g.publish(g.requestDestination(topic), msg)
response := newResponse(1)
response.write(<-f)
return response, nil
}
func subscribeHealth(g *Gilmour) {
health_topic := proto.HealthTopic(g.getIdent())
handlerOpts := NewHandlerOpts().SetGroup("exclusive")
g.ReplyTo(health_topic, func(r *Request, w *Message) {
topics := []string{}
resp_topic := proto.ResponseTopic("")
for t, _ := range g.getAllSubscribers() {
if strings.HasPrefix(t, resp_topic) || strings.HasPrefix(t, health_topic) {
//Do Nothing, these are internal topics
} else {
topics = append(topics, t)
}
}
w.SetData(topics)
}, handlerOpts)
}
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)
}
}