[wildfly-dev] WF 8.0 HTTP Upgrade help needed

[Jason T. Greene]

Let me play with your use case, although it will be a few hours before I can get to it.

There are some limitations to the spec, but they are manageable. As an example the write is actually written for you in a non blocking fashion. It's basically an async deferred write. 

The undertow http handler API is, in my opinion a much better fit for pure non-blocking / reactive applications. 

> On Apr 3, 2014, at 9:52 AM, Przemyslaw Bielicki <pbielicki at gmail.com> wrote:
> 
> 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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