[Armedbear-devel] How to get a fresh session or instance

[Mark Evenson]

> On Dec 9, 2014, at 23:06, Robert Dodier <robert.dodier at gmail.com> wrote:
> 
> Hi, is there a way to get a fresh session or instance of ABCL, short
> of reloading all the classes? Ideally I'd like to be able to have
> two or more instances which exist at the same time and are independent
> of each other.

The Lisp environment is a global singleton per JVM process, like that of any
other Lisp implementation is per OS process.  So, to get a fresh instance, one
would need to start multiple JVMs, just like one would have to start multiple
instances of, say, SBCL to get a “fresh session”.  Since starting JVMs can be
expensive time-wise, the Java ecology has developed numerous “drop-in” tools to
pre-initialize JVMs, of which the best known may be [drip][].

[drip]: https://github.com/flatland/drip

> I believe the answer to this question is "no", but I just want to make
> sure I am not overlooking something. If indeed it's not possible now,
> what would it take to make it happen? I see there is a certain amount
> of static data -- would it be necessary to replace that with
> (just for the sake of discussion) a hash table which takes a session
> or instance id as a key?
> 
> Any thoughts on this topic will be appreciated.

To carry forward the comparison with SBCL:  what would it take to make SBCL
have a “fresh instance”?  Maybe you don’t really want a “fresh instance” in
ABCL down to its initial state but some equivalent of save-image-and-die
restoration?  Unfortunately, I know of no mechanism in the Oracle-derived JVMs
that allow one to use mmap()-like facilities to load in a previously dumped JVM
instance.  I think that there once were commercial, non-free JVM
implementations available that would do this sort of thing (Terracotta?), but I
can’t find any mention of one in a quick web search.

Could you be more specific about your use case?

-- 
"A screaming comes across the sky.  It has happened before but there is nothing 
to compare to it now."






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