discard copy messages when more procs are started for the same copySrc request

requests_copy.go

@@ -326,6 +326,28 @@ func (m methodREQCopyDst) handler(proc process, message Message, node string) ([
 		// Create a new sub process that will do the actual file copying.
 		copyDstSubProc := newSubProcess(ctx, proc.server, sub, processKindSubscriber, nil)
 
+		// Check if we already got a sub process registered and started with
+		// the processName. If true, return here and don't start up another
+		// process for that file.
+		//
+		// NB: This check is put in here if a message for some reason are
+		// received more than once. The reason that this might happen can be
+		// that a message for the same copy request was received earlier, but
+		// was unable to start up within the timeout specified. The Sender of
+		// that request will then resend the message, but at the time that
+		// second message is received the subscriber process started for the
+		// previous message is then fully up and running, so we just discard
+		// that second message in those cases.
+
+		proc.processes.active.mu.Lock()
+		_, ok := proc.processes.active.procNames[copyDstSubProc.processName]
+		proc.processes.active.mu.Unlock()
+
+		if ok {
+			log.Printf(" * * * DEBUG: subprocesses already existed, will not start another subscriber for %v\n", copyDstSubProc.processName)
+			return
+		}
+
 		// Give the sub process a procFunc so we do the actual copying within a procFunc,
 		// and not directly within the handler.
 		copyDstSubProc.procFunc = copyDstSubProcFunc(copyDstSubProc, cia, message, cancel)