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From "Martin Jericho" <marti...@radiocity.com.au>
Subject Re: Streaming RPC calls
Date Mon, 23 Sep 2002 23:41:10 GMT

----- Original Message -----
From: "Rogerio Saran" <rsaran@organox.com.br>
To: <axis-user@xml.apache.org>
Sent: Tuesday, September 24, 2002 8:44 AM
Subject: Re: Streaming RPC calls


> Martin, forget webservices. Nowadays they are all about "pull" or
> "submit", and you want to "push" data.

I'm not too sure why you say I'm trying to "push" data.  All interaction is
initiated by the client.  Do I have an outdated notion of the terms push and
pull?

> Did you consider a messaging system?

No I haven't.  I thought SOAP would be the most appropriate because of the
cross-platform data encoding standard.  I haven't had much experience with
messaging.  Are there messaging systems out there that are cross-platform
and language independent?  I thought they were all tied to a particular
platform/language.  A built-in data encoding standard would also be very
nice, but not essential.  Do you have one in particular in mind?

>
> First, you probably want to chunk it to make each "delivery unit" more
> manageable. Next, you want them to be delivered as chunks, so a broken
> connection will not compromise the whole transfer. Finally you want it
> fast so you need to open several sockets at once.

I thought about this as well.  It was a compromise I was willing to make to
gain the benefits of soap.  I would certainly want the chunking to be
abstracted out of the API though.  I don't want to have to worry about it on
the application level.

>
> If you need to exchange a lot of data it does not makes sense to force
> it through a single TCP connection. Most servers have a limited ability
>   to reach high speed in a single connection due to TCP handshaking
> limitations.
>
> A quick and dirty recipe to transfer a zillion records of structured
> data as a stream:
>
> a) Again, forget webservices and RPC.
>     This is a raw data transfer problem.

That is exactly what it isn't.  It's not raw data, it's structured data.  It
has to be understood by different systems.  If I could borrrow the XML
encoding of SOAP and use it in a messaging system I would be all for it, but
that sounds suspiciously like SOAP again, only using a different transport
protocol.

>
> b) Chunk your data and pack it in well formed XML documents, making them
> suitable to be handled in lots of platforms.
>
> c) Send them through a messaging system. The simpler, the better. Is
> SMTP good enough? Go for it. If you want a sophisticated, "dog wags the
> tail" solution, there are also plenty of message-queue servers around.
>
> d) Need to ensure chunk sequence? Here you will cover your hands with
> some dirt to write a transport handshake mechanism, like windows in TCP.

Sequence doesn't matter too much, but the client needs to get an answer back
when the entire message has been processed successfully.  I did not want to
have the client acting as a server as well because of firewall issues, and
polling for the response is unresponsive and klunky, so SMTP is definitely
out of the question.

I'm certainly not committed to SOAP, but I would appreciate it if you could
give me a pointer to even one example of an appropriate messaging system.

Thanks
Martin

>
>
> *Saran
>
> Martin Jericho wrote:
> >
> >                 QUESTION 4:  All I really want to do is send a large
> >                 array of structured data in a platform independent way.
> >                 I would like to use the standard RPC encoding of SOAP to
> >                 avoid having to define my own XML schemas for the data,
> >                 but I'm not sure whether today's SOAP implementations
> >                 are mature enough to use for this purpose.  What do
> >                 other people do in this situation?  I can't imagine I'm
> >                 the only one.
> >
> >
> >                 Thanks
> >                 Martin Jericho
> >
> >
> >
> >
>
>
>


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