On Mar 14, 4:27 pm, pmf <phil.fr...@gmx.de> wrote:
> On Mar 14, 12:44 pm, Rock <rocco.ro...@gmail.com> wrote:
>
> > Hi all. I've been working on a piece of code (an xml-rpc server) in
> > Python (actually Jython), and one of its features is the capability of
> > loading modules (connectors in Java) during runtime. Not only are
> > these modules dynamically loaded on request (their names passed as
> > arguments in a string), but they are only visible in the lexical scope
> > of the specific method/function, the resources being released as soon
> > as that same scope is left.
>
> > Now, I would love to recode this stuff in Lisp, especially Clojure.
> > But is it possible to pull this off? From what I've been reading, it
> > actually doesn't seem like it.
>
> Loading namespaces and classes can be done fully dynamic at runtime
> (and this is actually the default behavior when you're not using the
> AOT-compilation capabilities of Clojure; regular late binding).
>
> To release the resources (classes loaded on demand), you'd have to use
> a dedicated classloader, since the JVM only unloads loaded classes
> when their classloader is GCd.
>
> As for lexically scoping loaded classes, is this a security issue or
> do you just want to avoid polluting the global namespace?
Well, basically the way things are now, my jython xml-rpc server
recieves a request to do a certain operation remotely (say on target
"foo") and consequently loads the specific connector (where I work, we
call it an agent) to perform the operation, for instance a SOAP
request for identity management and provisioning on a remote target.
The module gets loaded in Python (Jython) something like this:
proxy = __import__(name) # where name is a string
proxy.doOperation(*args)
After leaving the method where the above two lines of code are
located, the module stored in proxy is no longer accessible, and the
resources are released. That's cool because, even better than the
namespace, you don't clutter your memory with unused modules. We've
got around 50 agents at the moment, but we don't need to have them
loaded in memory at the same time, but only on demand obviously.
Rock
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