> On 24 Jul 2021, at 14:59, sebb <seb...@gmail.com> wrote:
>
> I'm trying to write a filter to add a banner to some HTML pages.
>
> I have used the following definition:
>
> ExtFilterDefine rebootbanner mode=output \
> intype=text/html outtype=text/html \
> cmd="add_banner.sh"
>
> The script contents boil down to:
>
> echo header
> cat
> echo footer
If they're HTML, that'll break badly! You'd need to add the header
and footer within the HTML <body>. Markup-aware filters will do that,
or you could (at fairly low risk) use a sed or regexp search-and-replace filter.
A second consideration is that with ExtFilter you're incurring two performance
penalties. Spawning an extfilter process (a CGI-equivalent overhead)
and pumping your data through the filter.
> This works fine for some pages, however other pages fail to display in
> a browser.
> Turns out that the issue is that the input to the filter is sometimes gzipped.
> The header causes issues for the browser display.
> How can I ensure that the filter is run before the output is gzipped?
It's many years ago so memory is hazy, but making filtering play nicely
with gzipped contents, particularly in a proxy situation, was one of the
main motivations behind both mod_filter and the INFLATE output filter in
mod_deflate. Revisiting the documentation I see the image downsampling
example in the mod_filter page applies the same principle (and also dates it -
that was for a proxy accelerator for mobile phones pre-3G).
--
Nick Kew
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