On Oct 4, 2007, at 8:20 AM, Alan Wright wrote:

> What exactly is Comet?  what problem does it solve? When would I  
> use it?

Comet is for streaming responses from the server, as a replacement  
for polling.  ("Comet" doesn't stand for anything, unfortunately.   
It's just a unique identifier.)  The server sends a new packet of  
data to the client when an event occurs.

The best example might be a Flash administration or monitoring  
application that updates the client dynamically as events arrive from  
the server.  The demo examples tend to be simpler, e.g. a chat  
application, which have the same basic properties as a real  
application, i.e. asynchronous updates, but might not be directly  

It's a somewhat specialized capability, but if the application needs  
async notification of the client, it's very useful for the app server  
to provide the infrastructure.

Resin's Comet is solving two problems

1) Async notification/communication of the servlet thread using the  
CometController.  This is the main issue, really.  The servlet thread/ 
request is single-threaded/synchronous, but Comet applications are  
intrinsically multithreaded/async.   Resin's implementation deals  
with most of the threading issues, which will let applications avoid  
threading issues later on.

2) Thread detachment and reattachment from the idle servlet request.   
While the Comet servlet is idle, waiting for the next event, Resin  
can detach the thread and use it for another request.  This is a nice  
side-effect and many comet implementations push #2, but really it's  
#1 that's the main issue.

-- Scott

> Alan
> Scott Ferguson wrote:
>> I've updated the Comet API to make it more like the Servlet API and
>> to avoid dependencies on Resin details.  Details are at
> -- 
> Alan Wright
> Athene Systems
> tel 0845 230 9803
> Athene Systems Limited
> Registered Office:
> Shieling House
> Invincible Road
> Farnborough
> GU14 7QU
> Registered in England and Wales No. 3156080
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