use case for runtime downloadable code

[Sim IJskes - QCG <si...@qcg.nl>]

Can somebody come up with a use case where it is absolutely necessary to 
download code at runtime, where the effort of downloading it upfront is 
so big compared to at runtime?

Gr. Sim

Re: use case for runtime downloadable code

[Sim IJskes - QCG <si...@qcg.nl>]

On 10/08/2010 09:10 AM, Patricia Shanahan wrote:
> An factory floor with unified control over software upgrade timing for
> the whole system, including all clients and servers, is the easy case.

Yes. You're right. Comparatively speaking :-).

> The more interesting problem is a long-running, 7/24, application that
> uses Internet-accessible services provided by many different
> organizations, each with their own, uncoordinated, upgrade schedule and
> policies.

But there is some kind of coordination. Namely the interface used by the 
calling code residing in the local codebase. And if you want to upgrade 
a service interface, with or without the availability of smartproxies, 
you still need to support both the old as the new interface.

Gr. Sim

Re: use case for runtime downloadable code

[Patricia Shanahan <pa...@acm.org>]

Sim IJskes - QCG wrote:
> On 10/07/2010 02:47 PM, Greg Trasuk wrote:
>> On Thu, 2010-10-07 at 05:36, Sim IJskes - QCG wrote:
>>> Can somebody come up with a use case where it is absolutely necessary to
>>> download code at runtime, where the effort of downloading it upfront is
>>> so big compared to at runtime?
>>>
>>> Gr. Sim
>>
>> Smart proxies.  Flexible protocols.  Two services offering the same
>> interface, one of which uses JERI and one of which uses an in-memory
>> handler.  Remote event listeners that do filtering on the "event
>> generator" side, and only go to the consumer if the consumer is really
>> interested in the event.
> 
> Thanks. But having preloaded smart proxies does not prohibit this, does it?
> 
> Do you deploy jini on the factory floor? How does that work in practice, 
> do you have a lot of sensors and actuators that you reset after a 
> software update? Or do you deploy a complete new codebase (in different 
> package combinations) over all the devices?

An factory floor with unified control over software upgrade timing for
the whole system, including all clients and servers, is the easy case.
That environment will probably also have unified control over virus
detection etc.

The more interesting problem is a long-running, 7/24, application that
uses Internet-accessible services provided by many different
organizations, each with their own, uncoordinated, upgrade schedule and
policies.

I thought the point of the Jini proxy system was to hide changes that do
not affect the interface, so that the application can, for example,
replace a service that has become unavailable or untrusted with a new
one that implements the same interface with minimal disruption.

Patricia

Re: use case for runtime downloadable code

[Sim IJskes - QCG <si...@qcg.nl>]

On 10/07/2010 02:47 PM, Greg Trasuk wrote:
> On Thu, 2010-10-07 at 05:36, Sim IJskes - QCG wrote:
>> Can somebody come up with a use case where it is absolutely necessary to
>> download code at runtime, where the effort of downloading it upfront is
>> so big compared to at runtime?
>>
>> Gr. Sim
>
> Smart proxies.  Flexible protocols.  Two services offering the same
> interface, one of which uses JERI and one of which uses an in-memory
> handler.  Remote event listeners that do filtering on the "event
> generator" side, and only go to the consumer if the consumer is really
> interested in the event.

Thanks. But having preloaded smart proxies does not prohibit this, does it?

Do you deploy jini on the factory floor? How does that work in practice, 
do you have a lot of sensors and actuators that you reset after a 
software update? Or do you deploy a complete new codebase (in different 
package combinations) over all the devices?

Gr. Sim

Re: use case for runtime downloadable code

[Greg Trasuk <tr...@stratuscom.com>]

On Thu, 2010-10-07 at 05:36, Sim IJskes - QCG wrote:
> Can somebody come up with a use case where it is absolutely necessary to 
> download code at runtime, where the effort of downloading it upfront is 
> so big compared to at runtime?
> 
> Gr. Sim

Smart proxies.  Flexible protocols.  Two services offering the same
interface, one of which uses JERI and one of which uses an in-memory
handler.  Remote event listeners that do filtering on the "event
generator" side, and only go to the consumer if the consumer is really
interested in the event.

"The end of protocols" is not just a concept.  To require fixed,
preloaded proxies is to tear the heart and soul out of Jini.

Cheers,

Greg Trasuk
-- 
Greg Trasuk, President
StratusCom Manufacturing Systems Inc. - We use information technology to
solve business problems on your plant floor.
http://stratuscom.com