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From Honza Pazdziora <>
Subject Re: I/O Layering in next version of Apache.
Date Tue, 22 Sep 1998 20:43:26 GMT
> >
> >Does anyone have a starting point for layered I/O? I know we kicked it


there has been a thread on modperl mailing list recently about
problems we have with the current architecture. Some of the points
were: what requerements will be put on modules to be new I/O
compliant. I believe it's the Apache::SSI vs. Apache::SSIChain
difference between 1.3.* and 2.*. The first fetches the file _and_
does the SSI, the second takes input from a different module that
either gets the HTML or runs the CGI or so, and processes its output.
Should all modules be capable of working on some other module's
output? Probably except those that actually go to disk or database for
the primary data.

Randal's point was that output of any module could be processed, so
that no module should make any assumption whether it's sending data
directly to the browser or to some other module. This can be used both
for caching, but it also one of the things to get the filtering

Also, as Apache::GzipChain module shows, once you process the output,
you may need to modify the headers as well. I was hit by this when I
tried to convert between charsets, to send out those that the browsers
would understand. The Apache::Mason module shows that you can build
a page from pieces. Each of the pieces might have different
characteristics (charset, for example), so with each piece of code we
might need to have its own headers that describe it, or at least the
difference between the final (global) header-outs and its local.

Sorry for bringing so much Perl module names in, but modperl is
currently a way to get some layered I/O done in 1.3.*, so I only have
practical experiance with it.


 Honza Pazdziora | |
                   I can take or leave it if I please

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