[wildfly-dev] WF 8.0 HTTP Upgrade help needed

[Stuart Douglas]

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 at gmail.com <mailto:stuart.w.douglas at 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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