Re: Embedded JavaSpaces

> Jeff Ramsdale wrote:
> > I've Googled around a bit and haven't had much success finding 
> > examples of folks using an embedded JavaSpace in their
applications.
> > It's not possible to run an embedded JavaSpace with the starter
kit
> > (Porter) code, is it? I belive Blitz and GigaSpaces both 
> have embedded
> 
> They (Blitz and GigaSpaces) do indeed.
> 
> Haven't really looked at Outrigger's code but I suspect it 
> wouldn't take much hacking around with the newly open-sourced 
> code to get an Outrigger running locally and passing 
> operations in and out of it.

Ok

> You might need to implement your own local transaction 
> manager to allow you to perform atomic operations but that's about
it.

I saw something about that in Blitz and didn't think through it. That
makes sense, though.

> > implementations--are there any others? I imagined it 
> wouldn't be hard
> 
> What criteria did you have in mind?

Basically I was hoping for transparent switchability between a local
and foreign JavaSpace based on a user configuration at runtime. That
is, a properties file could indicate whether the user wanted to run in
a local distributed mode. The embedded JavaSpace would always be used
but additionally the remote JavaSpace could be used if the appropriate
property were set.
 
> > to write one though I'm not sure my skills are up to the task. Any

> > comments? Links?
> >
> 
> Depends exactly what you want - how many of the features of a 
> JavaSpace do you really need?
> 
> IMHO (as an implementer), I'd say it was damned hard if you 
> need all the usual functionality, to write an implementation 
> yourself.  There are a surprising number of places where you 
> can get deadlocks, race conditions, state stability problems 
> and issues with blocking takes or reads (just when have you 
> considered all possible current matches?).

I clearly wasn't thinking it through all the way--I haven't yet delved
into transactions, so they didn't enter my thinking (I'll get there!).
We've written a wrapper for JavaSpace that deals with some of the
threading issues one runs into with normal JavaSpace use so I can
certainly understand the possibility for problems. (Incidentally, is
there a semi-standard way of interacting with a JavaSpace to deal with
the threading issues and notifies, etc., or does everyone write their
own helper utility?)

> > In my specific application I have work I want to expose to remote 
> > workers via a JavaSpace but I think it would work well to 
> have workers 
> > local to my application as well. So I imagine having two 
> Spaces--one 
> > local and one remote--that allow me to selectively remote 
> my work or 
> > not. I'd be interested in other implementation ideas too, 
> though I'm 
> > curious about the issue of embedded JavaSpaces...
> >
> 
> Can't really contribute any other ideas but ask me more 
> questions and I'll try and satisfy your curious nature :)

Don't know what I would add to the above. I imagined that it would be
a somewhat common pattern to have applications doing work that would
distribute some things and not others (perhaps based on
configuration), suggesting the pairing of a local JavaSpace with a
remote one. Guess not?

> Dan.

Jeff

| Jeff Ramsdale |
|   SolutionsIQ |
|  Bellevue, WA |
 

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