[Zope] [Fwd: Re: Zope Solution]

[Philipp Auersperg]

ok, 

there exist some main differences to things like CORBA or DCOM:

0. XMLRPC is more simple, sort of out-of-the-box

   you dont need very complicated Object Request Brokers for
   your client.
   You just need xmlrpclib.py, a small 20 K beast in your PythonPath,
   - no install of complicated ORB's on the client-side. 

   with python >= 2.0 xmlrpclib is included

1. XMLRPC itself is (only) late-bound - 
    with CORBA and DCOM you define interface by writing .idl 
    definition files and generate stub classes that you use 
    inside your client.

    DCOM can be also be used late-bound, I dont know about 
    CORBA in that matter.

    when your call to te server does not match to ot's interface 
    the error occurs an run-time. 
    
    This feature is not difficult to 
    live with for Python programmers, at least for me 8-)

2. Since XMLRPC is transported by HTTP it is stateless.
    
    when you do this:

      ob=xmlrpclib.Server('.........')
      ob.doThis()
      ob.doThat(bla,blorf)
      res=ob.getSomeResult()

    in CORBA/DCOM it creates an object reference that is held
    on the server-side during the whole transaction and released 
    when 'ob' comes out of scope or is intentionally released by 
    the client side.

    In XMLRPC the object reference is evaluated for every atomic 
    call to the server (see xmlrpclib.py for better understanding).

    the xmlrpclib.Server(...) just prepares the URL used by 
    xmlrpclib, it is not a real call to the server !!

    so in XMLRPC you have to design your Server so that 
    transactions have to happen within a single call to the server.
    If you know that you can deal with it.

3.  Performance.
    well, for every call xmlpclib has to marshal and unmarhal 
    ( thats the most effort ) your method calls as XML chunks.
    by default xmlrpclib uses xmllib.XMLParser (slow, but buiilt-in).
    but you can tune xmllib by using sgmlop (speeds up marshalling
    to 10-15x) 

    xmlrpc fits perfect for remote calls where you have few
    calls to functions to the server where each function 
    runs long compared to the transport time. 

    Design your interface so, that transactions can be done
    within single calls to the server !!

If you keep these primciles in mind xmlrpclib can make life easy!

phil
    



Am Fre, 2001-12-07 um 19.33 schrieb Jason Earl:
> 
> Hmm... I actually know *how* to use XML-RPC, in fact I think that it
> is incredibly slick.  Currently I am using it to enter email messages
> into a PostgreSQL database.  I already had the logic to do this in
> Zope, and so it seemed a shame to not reuse it.
> 
> So far this has worked really well, but I was concerned about how well
> tested this sort of thing is, and how well it scales.
>