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From Ashish <paliwalash...@gmail.com>
Subject Re: [MINA 3.0] Thougts about the selectors
Date Thu, 04 Feb 2010 13:10:27 GMT
Just thought it would be good if we can consider JCA stuff here. I
believe there was a discussion long ago, of using MINA under that
Not a master on JCA, but if we can consider this aspect as well, would be great.

On Thu, Feb 4, 2010 at 6:23 PM, Emmanuel Lecharny <elecharny@gmail.com> wrote:
> I have reviewed the way we use the Selector in MINA 2.0. Here are some of
> the thoughts I have about teh way we use them for Sockets :
> We currently have a system built on top of three elements :
> - IoAcceptor on the server side
> - IoConnector on the client side
> - IoProcessor which are processing the messages received or sent
> IoAcceptor and IoConnector are just two sides of the same coin : a
> IoService. The only difference is that the Connector initiates the
> communication.
> Nio Sockets
> ----------------
> In order to deal with incoming connections, the IoAcceptor uses a Selector
> on which are registered the ServerSocketChannel for the OP_ACCEPT event. On
> the client side, we have the same Selector but the ServerSocket is
> registered for the OP_CONNECT event.
> In both case, once the session is connected/accepted, the associated Channel
> is attached to another Selector, itself associated with an IoProcessor.
> Here, I'm questioning the fact that we use more than one Selector to handle
> connect/accept  and read/write operations. The select() operation is not
> specially costly, even if it does a lot of things :
> - deregister the canceled channels
> - each channel which has had some operation since the last select is put to
> a set of selected keys
> - deregister the canceled channels again (for channel which has been
> canceled while the step 2 was processed)
> - return the number of keys found ready in step 2
> but all in all, this is a fast operation, as it just reads some bit fields
> to determinate if something has changed since the last select. Even if we
> have one million registered keys in the selector, first the number of active
> channel will be low, and second the processing time for this step is very
> minimal compared to the application processing time.
> Now, wouldn't it be better to have only one selector, and then dispatch the
> tasks to some processor?
> On the server side, we have to deal with :
> - newly added sessions
> - recently closed sessions
> - incoming data
> - outgoing data
> On the client side, we have to deal with :
> - newly connected sessions
> - recently closed sessions
> - incoming data
> - outgoing data
> each of those tasks can be processed by a separate thread selected in a
> thread pool. IMO, it may be better than the current architecture where we
> have a pool of IoProcessor, each one of them having its own Selector, and no
> thread to process the events. For instance, if we have 3 IoProcessor (the
> default value for a dual core processor), then we can only process 3 events
> in parallel. Pretty inefficient...
> --
> Regards,
> Cordialement,
> Emmanuel Lécharny
> www.nextury.com


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