Jerome said earlier in this conversation: The only way I see to solve this issue for now (2.1) would be to maintain a > custom Restlet call stack containing the list of Filters that intercepted > the inbound call and make sure that their afterHandle() method is invoked > by the asynchronous response thread.
Trying to flesh this out in my head: So the same logic that calls beforeHandle would push the corresponding afterHandle call onto a stack associated with the response; setting committed false would prevent the normal afterHandle machinery from executing, and the commit() machinery would be given access to the stack so it could pop those afterHandles and call them? Afaict, this isn't in yet, so I think it would be safer to say that asynch I/O is still in preview mode for 2.1. Am I being too pessimistic? --tim On Thu, Dec 22, 2011 at 12:56 AM, Tal Liron <[email protected]>wrote: > I have created the simplest example I could to prove my point, and > hopefully to help find a solution to this important problem: > > https://github.com/tliron/restlet-async-test > > The current code works as expected -- but only because AsyncResource.delay > is non-zero. If you set the value to zero, then the Restlet chain will do > its work before the AsyncResource commits, and then the resource will not > return the entity. > > No exceptions get thrown -- the code is "thread safe" -- but it still > shows that it's impossible to reliably handle async responses. > > I hope other people can take a look and let me know if I missed something > important. > > > > Jerome, even though setCommitted(false) gets called, there still the > usual > > processing of handle() in the entire restlet chain (the Finder, > delegating > > to the UniformResource, etc.). Within these routines, the return values > from > > various callbacks are handled. Stuff that happens there on the response > can > > override work being done in another thread. The response is thread safe, > but > > it's still not the intended result. > > > > I don't have a test case right now, but it would be easy to produce: > simply > > call setCommitted(false) in a ServerResource annotated @Get > implementation, > > and immediately move processing to a thread, where commit() is eventually > > called. The worker handler thread would overlap with the work done in the > > regular Restlet handling thread and you would get weird statuses and > > response entities. > > > > The reason I suggest an exception (and I share Tim's unease with it) is > that > > it's a way to stop the handling chain in the regular thread, so that only > > the new handler thread would have free reign on the response. But it > doesn't > > have to be an exception. Another solution would be for ServerResource, > > UniformResource and Finder to be refactored specifically to handle the > > committed=false case. I worry, though, that future work or custom > > implementations would not handle the case properly. > > > > -Tal > > > > On Sun, Jul 11, 2010 at 9:00 PM, Jerome Louvel <jerome dot louvel at > noelios dot com>wrote: > > > > > Hi Tal and Tim, > > > > > > > > > > > > There is a way to signal an asynchronous response on a per-call basis, > > > calling Response#setCommitted(false). > > > > > > > > > > > > Then, if you call Response#commit() before the initial request thread > > > reaches back the connector, this should work fine as well. I’m not > sure yet > > > how it could get ‘corrupted’. Do you have a precise scenario? > > > > > > > > > > > > Note that the NIO version of the asynchronous internal connector has > been > > > moved to version 2.1. This feature should indeed be considered as > preview > > > feature for 2.0. > > > > > > > > > > > > Best regards, > > > Jerome Louvel > > > -- > > > Restlet ~ Founder and Technical Lead ~ http://www.restlet.org > > > Noelios Technologies ~ http://www.noelios.com > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > *De :* tpeierls at gmail dot com [mailto:tpeierls at gmail dot com] > *De la part de* Tim > > > Peierls > > > *Envoyé :* vendredi 18 juin 2010 13:51 > > > > > > *À :* discuss at restlet dot tigris dot org > > > *Objet :* Re: Status of Asynchronous Support > > > > > > > > > > > > I never saw a response to this, but it does seem like a problem. > > > > > > > > > > > > I don't love the idea of a special exception used purely to handle > control > > > flow, but I can't think of anything better off-hand. > > > > > > > > > > > > --tim > > > > > > On Sat, May 22, 2010 at 8:05 PM, Tal Liron <tal dot liron at > threecrickets dot com> > > > wrote: > > > > > > Hi Jerome, > > > > > > > > > > 2. There is a TaskService associated to your application that you > could > > > > leverage. It separates threads usage from tasks to process (such as > > > > committing responses). > > > > > > I've tried this, but there is a concurrency problem with this pattern > in > > > ServerResource -- > > > > > > If I set autoCommiting to false during a ServerResource.get() and put > my > > > task on a separate thread pool, then my own task might try to update > the > > > response at the same time as the upper parts of the call stack > > > (Finder.handle(), for example) also try to update the response > according > > > to my return value from get(). Both threads might be doing it at the > > > same time, and the response ends up corrupted (no concurrency > > > exceptions, but it's mismatched status/entity, for example). > > > > > > What would be the correct way to defer a response from within a > > > ServerResource? > > > > > > My thought is that there should be a way to return from get() while > > > signaling to the rest of the call stack that I am handling the > response. > > > A null won't work, because it internally signifies an unavailable > > > entity. Perhaps a new kind of ResourceException? > > > DefferedResponseResourceException? > > > > > > -Tal > > > > > > ------------------------------------------------------ > > > > > > > http://restlet.tigris.org/ds/viewMessage.do?dsForumId=4447&dsMessageId=2612147 > > > > > > > > > > > ------------------------------------------------------ > > http://restlet.tigris.org/ds/viewMessage.do?dsForumId=4447&dsMessageId=2899008 > ------------------------------------------------------ http://restlet.tigris.org/ds/viewMessage.do?dsForumId=4447&dsMessageId=2899155
