Re: Design Guidelines : Polling vs Events - Design and Architecture Discussion Boards

uroojkhan wrote:
How you covered (are covering) design patterns?

Like you I'm self studying design patterns (I've the book of Gamma, Helm, Johnson, Vlissides) and, like you, I find them quite challenging. I think that if you need one pattern in you project, then you'll have a chance to deeply understand it.

Smile | :)

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CPallini wrote:
I've the book of Gamma, Helm, Johnson, Vlissides

Thanks for the book (Design Patterns: Elements of Reusable Object-Oriented Software) reference.

CPallini wrote:
I think that if you need one pattern in you project, then you'll have a chance to deeply understand it.

True. But before using patterns we must have know how about it. Smile | :)

Thanks and Regards Rose | [Rose]

________________________________
Success is not something to wait for, its something to work for.

uroojkhan wrote:
But before using patterns we must have know how about it.

True, of course. But the book we wrote about is of big help, because it first identifies and clarifies the problem the pattern addresses, then explains the details of the pattern itself.

Cheers
Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

Hi,

uroojkhan wrote:
Thanks for the book (Design Patterns: Elements of Reusable Object-Oriented Software) reference.

You mau refer this book from here & here.

regards,
Divyang Mithaiwala
Software Engineer

Many thanks for the valuable links. I'm still searching the book because its not available in the local market Frown | :(

Regards

________________________________
Success is not something to wait for, its something to work for.

Hi,
I was wondering if there are some guidelines regarding the following issue in the .NET framework:
Polling based design (the client polls the server every X interval for changes) Vs. Events driven design (the client registers to the event and the server will raise the event)?
i am not sure when to use each of the above...

There is an alternative: Observers. Polling requires significant effort to keep state in sync so that you can keep track of changes. Events are good, but do require that items subscribe to the events to keep track of them.

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   In my experience, this depends greatly on the thing being interfaced with and the platform.

   For example, some hardware devices support interrupts and can raise an interrupt when something happens, and then data can be read from the device. Some others do not support interrupts and need to be polled (rapidly) so that any data is not missed.

   It may also depend on your platform. If targeting an battery-powered platform (or working with a battery operated device), polling can greatly reduce battery life over an interrupt-based approach.

   For what you suggest above, I would have clients register with the server and have the server fire off events as required. This is less work all around in the long run - network traffic only exists when something is actually happening, and the server is not going to be chewing up CPU cycles by always answering "no" each time a client connects and asks "is anything available?".

   Peace!

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Depends actually,
polling introduces a latency , which is equal to polling interval.
event's on other hand are instantaneous, so it depends whether a latency is accepted or not.

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Sebastian

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