[armedbear-devel] Questions for use in a server

[Erik Huelsmann]

Hi Blake,

On Sat, Jan 9, 2010 at 1:24 AM, Blake McBride <blake at mcbride.name> wrote:

> I am considering using ABCL as an extension language to a Web server app I
> have.

We just put quite a bit of research into getting ABCL to run on Google
App Engine, so it would be nice to learn about your experiences. I
think ABCL is up to the task.

> I know the answer to many of the questions I have in choosing the
> correct extension language and ABCL seems to fit the bill well.  I do have
> some questions, however.

> 1.  Can ABCL run concurrently in multiple threads without any problems (I
> understand the ramifications in terms of my application code)?

Yes. The same function can be run in any number of threads synchronously.

> 2.  I would like to have some utility code which is loaded once and shared
> by all the ABCL threads.  Each thread can then run code that is independent
> (i.e. they can have the same function names with different definitions).
>  (Perhaps I'd have to use packages for this.)

You will have to use packages for using the same functions with
different definitions: function definitions are a global property of a
symbol, but symbols are tied to packages. At this time, there's only a
single interpreter meaning that there's no way for different threads
to create separate environments.

> 3.  If I am running a lot of different threads will ABCL allow code to be
> GC'd when the thread ends (presuming no other thread is using that code)?

Yes. If all references to any object (including code objects)
disappear, that object will be GC-ed. We verified that this applies to
classes too (classes are used to implement functions). You'll need to
destroy the package after you're done using it to eliminate references
to the symbols (which in their turn refer to the code). Any function
which isn't referred to from a symbol may even be collected during
thread execution, if all references disappear.

> 4.  ABCL seems to have a somewhat heavy startup time.  This is okay for the
> first time, but I need the threads to start much faster (much less than half
> a second).

Right. That's no problem. The time used to start up ABCL (roughly 1
second on my system) is used to set up the singleton Interpreter
object and runtime environment. After that's been done, threads can be
created about as fast as Java can do it.

> Thanks for the answers!

Hope they help. If any questions remain - or new ones come up - don't
hesitate to ask!


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Heh. Just when I finish this reply, I see others have already answered
roughly the same things. Well, just for posterity I'll just send it.
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Bye,

Erik.