AW: [Caml-list] Master-slave architecture behind an ocsigen server.

[Gerd Stolpmann <info@gerd-stolpmann.de>]

Am 28.03.2013 10:18:28 schrieb(en) Philippe Veber:
> Thanks for your input Gerd! As I understand it, your suggestion is to  
> have
> an RPC server (based on netplex) doing the actual calculations. That  
> RPC
> server would be called by the ocsigen server when needed (the ocsigen
> server is the client in that scheme). So in that schema, only the RPC  
> call
> should be lwt-friendly. Digging in ocamlnet documentation, it seems  
> that
> could be achieved using [Rpc_simple_client.call] wrapped inside a
> [Lwt_preemptive.detach].

I guess RPC would be most convenient here - it supports a server mode  
where the child processes accept the new connections (btw, if you don't  
want to deal with the RPC encoding stuff (i.e. XDR), just marshal the  
OCaml value as string, and use RPC functions that are declared as  
string->string).

A sample program would the "finder" service here:

http://projects.camlcity.org/projects/dl/ocamlnet-3.6.3/examples/rpc/finder

Gerd

> This would be more complex than using nproc, but if it is effectively
> dangerous/impossible to fork the ocsigen server process (as required  
> to use
> nproc), that seems a feasible solution for me --> I might ask a  
> couple more
> questions later then.
> 
> Danke sehr!
> ph.
> 
> 
> 
> 2013/3/27 Gerd Stolpmann <info@gerd-stolpmann.de>
> 
> > Am Dienstag, den 26.03.2013, 15:29 +0100 schrieb Philippe Veber:
> > > Dear all,
> > >
> > > I'm developping an ocsigen website doing some scientific  
> calculations.
> > > Up to now, the calculations were done in the same process that  
> runs
> > > the server. In order to gain in scalability (and maybe stability  
> too),
> > > I would like to run those calculations in a separate (pool of)
> > > process(es). As this is a pretty typical setup, I guess quite a  
> few
> > > people have already done that. So I'd like to hear some  
> suggestions on
> > > what library to use in this particular context. It seems to me  
> that
> > > the release library [1] should do the job and is lwt-friendly, but
> > > there are maybe other good options?
> >
> > Well, I don't know whether this is an option for Ocsigen users, but
> > Ocamlnet includes fairly good multiprocessing support. You can run
> > servers that dynamically start subprocesses on demand. Look for  
> Netplex:
> >
> >
> >  
> http://projects.camlcity.org/projects/dl/ocamlnet-3.6.3/doc/html-main/Intro.html#netplex
> >
> > I've no good recipe, though, how to plug in service processors that  
> base
> > on lwt (well, there is an adaptor in Ocamlnet for lwt - Uw_lwt -  
> but I
> > wouldn't know what to do on the Ocsigen side, but maybe worth
> > exploring).
> >
> > Ocamlnet also includes other mechanisms that are generally  
> interesting
> > for compute stuff, namely Netmulticore for exploiting several cores  
> on
> > the same machine with fast shared memory architecture, and RPC for
> > distributing computations in a network. Both are extensions of  
> Netplex,
> > so it is easy to integrate into a single program.
> >
> > Gerd
> >
> > > Thanks for any hint, cheers!
> > >
> > > Philippe.
> > >
> > > [1] https://github.com/andrenth/release
> > >
> >
> > --
> > ------------------------------------------------------------
> > Gerd Stolpmann, Darmstadt, Germany    gerd@gerd-stolpmann.de
> > Creator of GODI and camlcity.org.
> > Contact details:        http://www.camlcity.org/contact.html
> > Company homepage:       http://www.gerd-stolpmann.de
> > *** Searching for new projects! Need consulting for system
> > *** programming in Ocaml? Gerd Stolpmann can help you.
> > ------------------------------------------------------------
> >
> >
> 
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-- 
------------------------------------------------------------
Gerd Stolpmann, Darmstadt, Germany    gerd@gerd-stolpmann.de
Creator of GODI and camlcity.org.
Contact details:        http://www.camlcity.org/contact.html
Company homepage:       http://www.gerd-stolpmann.de
------------------------------------------------------------