fix(broadcast): checks whether a client req has arrived immediately

Author: aleksander-vedvik

broadcast/processor.go

@@ -57,6 +57,30 @@ func (p *BroadcastProcessor) handle(msg *Content) {
 	p.initOrder()
 	// connect to client immediately to potentially save some time
 	go p.router.Connect(metadata.OriginAddr)
+	if msg.IsBroadcastClient {
+		// important to set this option to prevent duplicate client reqs.
+		// this can be the result if a server forwards the req but the
+		// leader has already received the client req.
+		metadata.HasReceivedClientReq = true
+		go func() {
+			// new.Ctx will correspond to the streamCtx between the client and this server.
+			// We can thus listen to it and signal a cancellation if the client goes offline
+			// or cancels the request. We also have to listen to the p.ctx to prevent leaking
+			// the goroutine.
+			select {
+			case <-p.ctx.Done():
+			case <-msg.Ctx.Done():
+			}
+			// when the processor returns it sets p.cancellationCtxCancel = nil.
+			// Hence, it is important to check if it is nil. Also, the processor
+			// calls this function when it returns.
+			if p.cancellationCtxCancel != nil {
+				p.cancellationCtxCancel()
+			}
+		}()
+		p.log("msg: received client req", nil, logging.Method(msg.CurrentMethod), logging.From(msg.SenderAddr))
+	}
+	// all messages should always have a ReceiveChan
 	if msg.ReceiveChan != nil {
 		if !p.isInOrder(msg.CurrentMethod) {
 			// save the message and execute it later