services, take 1

[Hinkmond Wong]

On 12/21/2011 2:51 AM, Alan Bateman wrote:
> On 20/12/2011 23:28, Hinkmond Wong wrote:
>>
>> :
>>
>> For the Embedded market, it's not just about the registration and 
>> life cycle part of a container environment (such as OSGi on an 
>> embedded device) that is important, but also the minimal required 
>> runtime dynamic memory and static footprint size that is very 
>> important in being the smallest size possible (better even if it can 
>> dynamically grow and shrink depending on what services are running).
> With Jigsaw then module class loaders will be created and GC'ed when 
> unreachable as you would expect. This includes modules that provide 
> implementations of service types. There is an implementation issue/bug 
> at moment that will prevent module loaders from being GC'ed but we're 
> sort that out.
>
> In any case, I think part of the issue here is that the term "service" 
> means different things to different people. When you say "services are 
> running" then it makes me think of examples like a wireless service or 
> http service or something that involves its own threads or resources. 
> With the current effort here then the focus is on getting simple 
> service provider interfaces working with the module system. I've no 
> doubt there is there is a need to have dynamic services, service 
> registries and other things but not clear to me that all of this needs 
> to be the core.

Agreed.  I think more feedback from customers and developers (such as 
comments from here on this alias) will help greatly in shaping what is 
needed for dynamic services and dynamic service registries, in what is 
required to utilize the Jigsaw core to its fullest potential (especially 
on resource constrained embedded devices).


>>
>> When real-world embedded customers mention their desires for Jigsaw, 
>> it typically involves the ability to dynamically adjust the size of 
>> the underlying Java platform core libraries according to the needs of 
>> the runtime environment, possibly requiring the modules to be more 
>> dynamic and to minimize the platform's impact to device resources.
> Clearly having a modularized platform will go a long way to meeting 
> some of these needs. However minimizing footprint at runtime or doing 
> space/performance tradeoffs based the available resources is going 
> require a lot of additional work.


Yes, agreed, and balanced by the added-value that minimizing both 
dynamic and static footprint helps the Embedded Device market.  (As long 
as those interested in this topic voice up with their feedback that is.  
;-) )


Thanks,
Hinkmond

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