logging/tuning reconnect of event source

Signed-off-by: Stephan Richter <s.richter@srsoftware.de>

bus/src/main/java/de/srsoftware/umbrella/messagebus/MessageApi.java

@@ -42,6 +42,9 @@ public class MessageApi extends BaseHandler{
 		ex.sendResponseHeaders(HTTP_OK,0);
 		try (var os = ex.getResponseBody(); var stream = new PrintWriter(os); var eventQueue = new EventQueue(addr)){
 			LOG.log(INFO,"{0} opened event stream.",addr);
+			stream.print("retry: 3000\n\n");
+			stream.flush();
+
 			var counter = 0;
 			while (!stream.checkError()){
 				sleep(100);

frontend/src/urls.svelte.js

@@ -22,6 +22,9 @@ export function eventStream(createHandler,updateHandler,deleteHandler){
 	if (createHandler) es.addEventListener('CREATE', createHandler);
 	if (updateHandler) es.addEventListener('UPDATE', updateHandler);
 	if (deleteHandler) es.addEventListener('DELETE', deleteHandler);
+	es.onerror = (err) => {
+		console.log("SSE error (reconnecting automatically):", err);
+  	};
 	return es;
 }