Przemyslaw Bielicki wrote:

I tried - exactly the same results.

Another weird observation is that ServletOutputStream.isReady() is
returning true even after the connection is closed
(ServletInputStream.isFinished() is correctly returning true).

Here's the scenario that works but I can write back the data only once:
1. In HttpUpgradeHandler I set only  the ReadListener
2. I switch the protocol and send some data
3. ReadListener gets activated i.e. onDataAvailable() is called.
4. I process the input data, read as much as possible and put the input
into the queue
5. From within ReadListener I set the WriteListener
6. WriteListener.onWritePossible() gets called and I process the data -
I clean the queue
7. As long as I'm in WriteListener.onWritePossible()
(while.out.isReady() is constantly returning true, which is a correct
bahavior) the ReadListener is on-hold. I can send as much data as I like
but onDataAvailable() is not called
8. Only when I leave WriteListener.onWritePossible() method the
ReadListener.onDataAvailable() is called again and I can consume the
input data again.
9. I can process the input data again i.e. put it into the queue but
WriteListener.onWritePossible() is never called again. When I try to
reset it I get IllegalStateException

Either the specification or implementation seem not very mature....
Wildfly behavior is consistent with the one of Tomcat.

As Remy said this is expected.
Basically there is only ever one IO thread per connection, so only one method will be active at a time.

The reason why your listener method is not being called again would become apparent if you look at the javadoc for the read/write listeners:

Subsequently the container will invoke this method if and only
if {@link javax.servlet.ServletOutputStream#isReady()} method
has been called and has returned <code>false</code>.

Basically what this means is that the listener is only invoked if isReady() returns false at some point. If you have read some data and then you want to echo it you should call the onWritePossible method yourself, after you have received the data.

Stuart

At the moment I conclude that the non-blocking write is not possible in
Servlet 3.1.

I would appreciate if someone can provide an example that actually works
or explain why the weird behavior I observe is correct (is it?)

Cheers,
Przemyslaw




On Thu, Apr 3, 2014 at 6:18 AM, Stuart Douglas

<stuart.w.douglas@gmail.com <mailto:stuart.w.douglas@gmail.com>> wrote:

    Can you try with the latest development build of Wildfly (from

    https://ci.jboss.org/hudson/__job/WildFly-latest-master/
    <https://ci.jboss.org/hudson/job/WildFly-latest-master/>).

    There have been some fixes in this area, so your problem may have
    already been fixed.

    Stuart


    PB wrote:

        Hi,

        I'm testing the HTTP Upgrade feature of WF 8.0 and I'm facing
        some banal
        problem. Basically my ReadListener is NEVER called.
        Here's the code:

        @WebServlet(urlPatterns = "/upgrade")
        public class UpgradeServlet extends HttpServlet {
            @Override
            protected void doGet(HttpServletRequest req, HttpServletResponse
        resp) throws ServletException, IOException {
              if

        ("upgrade".equalsIgnoreCase(__req.getHeader("Connection"))) {
                req.upgrade(EchoHandler.class)__;

              }
            }
        }

        public class EchoHandler implements HttpUpgradeHandler {
            @Override
            public void init(WebConnection wc) {
              try {
                ServletInputStream in = wc.getInputStream();
                ServletOutputStream out = wc.getOutputStream();

                BlockingQueue<String> queue = new
        LinkedBlockingQueue<String>();
                in.setReadListener(new EchoReadListener(queue, in));
                out.setWriteListener(new EchoWriteListener(queue, out));
              } catch (IOException e) {
                throw new IllegalStateException(e);
              }
            }

        public class EchoReadListener implements ReadListener {
            @Override
            public void onDataAvailable() throws IOException {
              while (in.isReady()) {
                int length = in.read(buffer);
                String input = new String(buffer, 0, length);
                if (false == queue.offer(input)) {
                  System.err.println("'" + input + "' input was ignored");
                }
              }
            }

        I'm connecting to WF using telnet and sending the upgrade request:
        GET /example-webapp/upgrade HTTP/1.1
        Host: localhost
        Connection: upgrade
        Upgrade: echo

        and I'm getting correct response:

        HTTP/1.1 101 Switching Protocols
        Connection: Upgrade
        X-Powered-By: Undertow 1
        Server: Wildfly 8
        Content-Length: 0

        which means that from now on the protocol between my telnet
        client and
        WF is pure TCP.
        So, I start typing some text, hit Enter and.... nothing happens.
        onDataAvailable() is NEVER called. More so, this makes WF totally
        irresponsive - my whole webapp is dead.

        I believe, I'm doing something wrong - any ideas what exactly?
        There is
        also a slight chance that Upgrade feature in WF is f****d :)
        Anyway, WF should not block even in case my upgraded protocol is not
        working correctly?

        Many thanks,
        Przemyslaw

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