JS EventSource receiving mysterious error from my 3.0 async servlet

My EventSource connects, the output gets printed, but when I call asyncContext.complete() my JS EventSource receives an error. The errors for EventSource never bear a message.

For those who voted to close: It would be nice if you provided a reason next time. I even posted link to the Git project. What else is one supposed to do? o.O

Tested with Tomcat 7.0.30, 7.0.59, 8.0.20

The response returns with http status OK/200 and following headers:

• Connection: close


• Content-Type: text/event-stream;charset=UTF-8


• Date: Sat, 28 Feb 2015 21:32:35 GMT


• Server: Apache-Coyote/1.1


• Transfer-Encoding: identity

In case anyone would be willing to try here's the minimized Maven project: BitBucket.org

I tried things like turning my antivirus SW off.

Can you see anything suspicious here, please?

JS:

function setupEventSource() {
    var es = new EventSource('/sse');
    es.onerror = function(event) {
        console.log('[EventSource] Error while connecting to ' + es.url);
        // es.close();
    };
}
setupEventSource();

Java:

@WebServlet(urlPatterns = { "/sse" }, asyncSupported = true)
public class EventSource2 extends HttpServlet {
    private static ScheduledExecutorService executor = Executors
        .newScheduledThreadPool(10);

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) 
        throws IOException, ServletException {
        response.setContentType("text/event-stream");
        response.setCharacterEncoding("UTF-8");

        final AsyncContext asyncContext = request.startAsync();

        Runnable runnableDummy = new Runnable() {
            @Override
            public void run() {
                try {
                    PrintWriter writer = asyncContext.getResponse().getWriter();
                    for (int i = 0; i < 5; i++) {
                        Thread.sleep(1000);
                        writer.println("data: Hello " + i + "\n");
                        writer.flush();
                    }
                } catch (IOException e) {
                    throw new RuntimeException(e.getMessage(), e);
                } catch (InterruptedException e) {
                    throw new RuntimeException(e.getMessage(), e);
                }

                asyncContext.complete();
            }
        };

        executor.execute(runnableDummy);
    }

    @Override
    public void destroy() {
        executor.shutdown();
    }
}

server.xml

<Connector port="80" protocol="HTTP/1.1"
    URIEncoding="UTF-8" connectionTimeout="20000" asyncTimeout="20000" />