Re: [xml] IO callbacks are not thread-safe

[Michael Ludwig <mlu as-guides com>]

Petr Pajas schrieb:
> On Monday 06 April 2009 18:36:25 Michael Ludwig wrote:

> > If someone has time to explain this to the uninitiated: What are
> > these input and output callbacks of libxml? Or are they not part of
> > the Perl interface, just part of the C interface?
>
> Hallo Michael,
>
> This is a feature of libxml2, avalable in Perl bindings via the
> XML::LibXML::InputCallback module. The callbacks allow you to bypass
> the "normal" way libxml2 retrieves data from URLs. You can register
> callbacks that recognize which URL you want to handle differently and
> feed any content to the parser. You can use it to do things like URL
> rewriting or using special URL schemes to pull data from a database or
> other application specific resource.

Thanks Petr and Nick (off-list) for your replies. I feel less ignorant
now.

> The scenario discussed here is Apache web server using threads instead
> of forks to serve content to concurrent clients.

> > And can you control the number of processors to be engaged by Perl?
>
> Well, these are not Perl threads (i.e threads within one Perl
> interpreter) we are talking about, these are multiple thread each of
> which can run its own Perl/PHP or whatever interpreter.

So multi-threadedness for libxml2 (loaded once in memory), but not for
Perl, which is started several times? Is that about accurate?

> Perl threads are a different and ugly beast: do not use them unless
> you want your application to get much much slower, which you don't.

These are Perl interpreter threads, or ithreads, I guess. Haven't been
able to find much documentation about them, which suggests they're not
in use, which suggests it's not worth while using them.

> Please use perl-xml listserv activestate com for discussion specific
> to Perl- bindings.

I'll do that. Thanks again!

Michael Ludwig