Re: [Xen-devel] a last comment on xml-rpc

[Anthony Liguori <aliguori@xxxxxxxxxx>]

Ronald G Minnich wrote:
> I think Xen made the right decision, in the beginning, to use s-exprs. 
> We have heard from any number of places that learned the hard way that 
> XML is a really poor foundation for RPC.
> I hope you will reconsider going to XML-RPC. I don't think the 
> existence of python support is sufficient. The whole point of RPC, in 
> fact, is to let any client talk to any server, without regard to 
> language or environment. We know in practice that trivial C programs 
> can use s-expression based RPC; we've seen how awful the XML parsers 
> in C can be; do you really want to lock C out of this picture?
I don't think that's fair at all.  I've written the C code to interface 
with Xend using S-Expression/HTTP and it's painful (see libvirt).
I've also written an XML-RPC interface to Xend in C using libxml2.  It 
very little code and just works.  Granted, parsing XML is more painful 
that parsing S-Expressions but there are so many libraries for so many 
languages that XML parsing is really a nop.
I don't see any point in rolling out our own RPC mechanism when a 
standard one exists that is well supported in most languages.  There is 
also a C library that provides support for XML-RPC (libxmlrpc_c) so 
interfacing with Xend using C would require no additional code on the 
client side.  All the major high level languages I know of have XML-RPC 
support as part of the standard library.
We're talking about a pretty significant reduction in code in Xend too 
by moving to XML-RPC.  If Python supported a different RPC mechanism I 
would support moving to that simply to reduce the complexity of Xend.
Regards,

Anthony Liguori
> thanks
>
> ron
>
>
>
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