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Bandwidth constraint [message #762712] Thu, 08 December 2011 14:35 Go to next message
Xavipen Mising name is currently offline Xavipen Mising nameFriend
Messages: 59
Registered: March 2011
Member
Hi,

It is being considered to use RAP to developed an application for Monitoring and Control of remote equipment. The main constrain that we have is that the bandwidth available will be round 200Kbps or event smaller.

I do not know if this is the right place to ask but, is there a way to control/buffer the updates in the server before being send to the client?

The application have a set of counters that are going to be updated quite often and we are afraid that this will have an impact on the bandwidth. I have tried to find some documentation regarding the bandwidth usage of the RAP application but i could not find anything. Some pointer towards were to find this information would be also appreciated.

Regards,
Javi
Re: Bandwidth constraint [message #763714 is a reply to message #762712] Sat, 10 December 2011 11:36 Go to previous message
Ralf Sternberg is currently offline Ralf SternbergFriend
Messages: 1313
Registered: July 2009
Senior Member

Hi Javi,

> It is being considered to use RAP to developed an application for
> Monitoring and Control of remote equipment. The main constrain that we
> have is that the bandwidth available will be round 200Kbps or event
> smaller.

This will probably slowdown the initial loading of the library (~200kB
with gzip compression). However, these resources are being cached in the
browser, so it only affects the first access. Once the application is
running, the single requests and responses are usually very small
(mostly <1kB), but this size depends a lot on the complexity of the ui
that is being rendered. Latency is a more critical factor than bandwidth.

So it's hard to make a general statement here, to be sure, you should
run a test application in your target environment. Make sure to enable
compression on the server and to run in standard mode.

> I do not know if this is the right place to ask but, is there a way to
> control/buffer the updates in the server before being send to the client?

No, this wouldn't make sense. The requests are issued by the client, and
the server has to answer. Not including available information in the
responses would not reduce traffic, but let client and server run out of
sync.
What you can do is limiting the number of requests sent by the clients
by attaching listeners sparingly. The client will only issue a request
when the state of a widget changes AND there is server-side code to be
executed for this change.

> The application have a set of counters that are going to be updated
> quite often and we are afraid that this will have an impact on the
> bandwidth.

Since the requests and responses are very small, I would really suggest
to run some tests before thinking about optimizations. Chances are that
your concerns turn out to be invalid.

If the counters update the UI very frequently without user interaction,
i.e. from background threads, you may consider using polling instead of
a UICallback [1].

> I have tried to find some documentation regarding the
> bandwidth usage of the RAP application but i could not find anything.
> Some pointer towards were to find this information would be also
> appreciated.

I don't know of any such documentation. As I said, the bandwidth usage
of a RAP application greatly depends on the complexity of the UI and the
usage patterns it induces (e.g. click rates, UI refreshes, etc.). No
reasoning can replace performance tests.

Hope this helps,
Ralf

[1]
http://help.eclipse.org/indigo/index.jsp?topic=/org.eclipse.rap.help/help/html/advanced/server-push.html

--
Ralf Sternberg

Twitter: @EclipseRAP
Blog: http://eclipsesource.com/blogs/

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http://eclipsesource.com/services/rap/
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