Hi Tal,

1. This is a good point that needs to be explored. The current path we are
following is to deal with high-load directly inside the internal connector,
for example to stop accepting new connections at IO level if we are
overloaded, or giving a priority of responses sending over new requests
handling. 

You might prefer to deal with that inside resources, which could make
perfect sense. We should explore this during the 2.1 development cycle. Feel
free to enter a RFE in the tracker.

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).

Your point about instrumentation is valid though, we need to work on that.
Creating a RFE would be a good step forward.

3. abort() should now work with other connectors AFAIK (check the changes
log). Regarding provisional responses and commit(), I think this will have
to wait for 2.1. 

4. The internal connector is described here:
http://wiki.restlet.org/developers/172-restlet/354-restlet.html

We are working on the NIO enhancements to it and hope to have this ready for
2.0 in order to have a scalable/asynchronous/lightweight connector. It uses
a configurable thread pool, but HTTPS is not planned for 2.0 at all (too
much work).

We also have this page describing the various connectors available:
http://wiki.restlet.org/docs_2.0/13-restlet/27-restlet/325-restlet/37-restle
t.html

This should be improved I guess with addition details/criterias. We did
cover those details in the "Restlet in Action" book (early access).

5. Currently, we call this default connector the "internal" connector. I'm
not sure about having a code name for it at this point... I'd prefer people
to think about it as a natural part of the Restlet engine. 

Best regards,
Jerome Louvel
--
Restlet ~ Founder and Technical Lead ~ http://www.restlet.org
Noelios Technologies ~ http://www.noelios.com




-----Message d'origine-----
De : Tal Liron [mailto:tal.li...@threecrickets.com] 
Envoyé : jeudi 20 mai 2010 11:00
À : discuss@restlet.tigris.org
Objet : Status of Asynchronous Support

Thought I've followed what I could of the progress on asynchronous 
support, I have a few interdependent questions and suggestions.

1. On the one hand, I really like how simple asynchronicity is handled. 
I can defer my response to later (from another thread). But, Restlet 
provides no tools to help me decide if I should defer or not. What I 
would want to know is -- Am I under load right now, meaning high 
concurrency? Should I yield so that other requests can have a chance to 
get in?

2. A related question: If I do defer, I do not necessarily want to 
decide on my own when to finish the response. I might want to wait until 
there is a free thread that can take me. It would be great if there were 
1) a callback for this, or 2) a way for me to "signal" that I'm ready to 
respond, as soon as the server is free. Or, at the very least a way to 
poll the server load.

(To summarize these two issues: the Restlet server is very opaque right 
now. For truly scalable applications (cloud, cloud, cloud) we need 
realtime information from it so that the application can react dynamically.)

3. I know that the "default" connector supports commit/abort, but what 
about Grizzly, Jetty and Netty? If they don't support it yet, is support 
being planned for 2.0? This will strongly affect my deployment strategies.

4. Assuming only the "default" connector is asynchronous, could you 
provide more details about it? Until now, frankly, I've ignored it as 
something that just works and isn't fit for production. It seems like 
this connector is very capable by now, but I know nothing about how it's 
implemented. NIO? Thread pools? SSL? I think it would be very good if 
there were a wiki page with an in-depth comparison of the various 
available connectors, what features they provide and implementation 
details -- both of the servers themselves, and of the features the 
Restlet adapters leverages (or not). As it stands, it's hard for a 
deployer to make an informed decision on which connector to use.

(For the record -- I think benchmarks are quite useless for this 
comparison. Performance != scalability, and in any case benchmarks are 
highly contextual. It's very easy to switch connectors in Restlet and 
for people to do their own benchmarks.)

5. Might I suggest giving the "default" connector a name? It seems to be 
a nice little engine of its own. If we're going to start comparing it to 
the others as a viable alternative, it might be easier to name it. My 
only name suggestion is Thier Engine, short for Thierry, and reminds me 
of "tier." :)

-Tal

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