[wildfly-dev] WF 8.0 HTTP Upgrade help needed

[Przemyslaw Bielicki]

As I showed  I'm not able to read and write at the same time using
non-blocking IO, as promised by Servlet 3.1. I'm able to read using
non-blocking IO but my writes are blocking and I'm looking for the solution.

Regarding concurrent access, HTTP Upgrade promises that the upgraded
protocol will be full-duplex, so I should be able to read and write
concurrently but I'm not.

Another comment is that Servlets 3.1 is actually async ONLY from the server
point of view - the client is still blocked because HTTP 1.1 is synchronous
(we have to wait for HTTP 2.0 to solve this). Here Upgrade should help as
it is a pure TCP, so I'm the master of my protocol and I'm no longer bound
to HTTP - I can be as asynchronous as I want. Unfortunately Servlet 3.1 API
does not respect this.

It looks like the specification is not meeting the promises given....


On Thu, Apr 3, 2014 at 4:41 PM, Rémy Maucherat <rmaucher at redhat.com> wrote:

> On 03/04/2014 15:21, 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.
> >
> > 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?)
> This looks as expected (although Tomcat 8 should concurrently call
> read/write in upgraded mode, as a proprietary extension to be able to
> implement Websockets on top of Servlets 3.1, besides that Servlet 3.1 is
> still not concurrent, so at most one thread processing a request a given
> time).
>
> Non blocking IO means it allows avoiding to block on IO, it doesn't
> imply anything else. Servlets 3.1 is actually async IO (similar to NIO2,
> rather than NIO1), since non blocking IO is unusable as is.
>
> Rémy
>
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