Ok, I agree that the single file is probably the simplest approach for
the bootstrap, so long as a file is used only for the bootstrap and
everything thereafter is based on messaging.
Tony: by LAN all I meant was not wide-area networking (not grid). I think this bootstrap business only needs to work on a single computer, and once we get into something which is network-based and hides the implementation, it should be possible to do more general distributed computing as well. Hence we can probably largely ignore the more general case for now.
On Fri, 16 Feb 2007, John Taylor wrote:
> On 15 Feb 2007, at 18:18, Mike Fitzpatrick wrote:
>> For this exercise we should concentrate on what information needs to be
>> written to establish the connection and pass messages.
>
> A typical file looks like this:
> plastic.xmlrpc.url=http\://10.0.0.12\:8001/4200a0f243b49ebc/xmlrpc
> plastic.version=0.5
> plastic.rmi.port=1099
Anything which is just a set of keyword-value pairs in a text file with a simple syntax should do just fine. XML would be overkill for this purpose.
> Can anyone explain to the group what XPA does?
It would be best to hear from the SAO folks about this (Eric Mandel originally developed XPA), but here are some words from their web page. You can find out more at http://hea-www.harvard.edu/RD/xpa/.
The XPA messaging system provides seamless communication between many
kinds of Unix programs, including X programs and Tcl/Tk programs. It
also provides an easy way for users to communicate with these
XPA-enabled programs by executing XPA client commands in the shell
or by utilizing such commands in scripts. Because XPA works both at
the programming level and the shell level, it is a powerful tool for
unifying any analysis environment: users and programmers have great
flexibility in choosing the best level or levels at which to access
XPA services, and client access can be extended or modified easily
at any time.
A program becomes an XPA-enabled server by defining named points of
public access through which data and commands can be exchanged with
other client programs (and users). Using standard TCP sockets as a
transport mechanism, XPA supports both single-point and broadcast
messaging to and from these servers. It supports direct communication
between XPA clients and servers, or indirect communication via an
intermediate message bus emulation program. Host-based access control
is implemented, as is as the ability to communicate with XPA servers
across a network.
The original implementation was based on X, but the most recent version appears to be purely socket-based.