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From Rob Hartill <>
Subject Re: idea - last-modified despite SSI - possible performance booster
Date Sun, 02 Feb 1997 00:41:57 GMT
On Sat, 1 Feb 1997, Nathan Neulinger wrote:

> By returning a timestamp with more of these documents, this could lead to a
> major performance increase since the pages could be cached, whereas now
> they can't be.

You can use "Expires" and "Cache-Control" to make SSI document cacheable.
Almost 100% of my HTML output is SSI parsed (again for standard includes
but also to insert banner ads).

For the standard includes (page footers), I added a PerlHandler
(mod_perl) to cache the fixed messages at server startup then intercept
the SSI requests for them so they get served from memory not disk. Dunno
what it saves, but it gives warm fuzzies just thinking about it.

> For example, consider the following cases:
> ---
> 1. SSI is on for the file (it's a text/html file), but the file doesn't
> contain any SSI directives.
> Obviously in this case, there is no reason that the last modification date
> of the file couldn't be returned.

You'd need to process the entire file before knowing it has no SSI, that
means buffering it before the headers are finalised.

> ---
> 2. File with a ssi directive to include another file that contains no ssi
> directives
> In this case, the last modification date returned should be the more recent
> of the parent document or the included file.

Same problem as (1)

> ---
> 3. File with a ssi directive to include a file that also has ssi directives
> to include some non-ssi files.
> Just as in #2, return the most recent timestamp.


> ---
> 4. File with a #echo, #exec, #include of a command, etc., or a file that
> #includes a file that does one of those.
> In this case, don't return a timestamp, since it changes every time.


> --------
> -- Nathan
> ------------------------------------------------------------
> Nathan Neulinger                  Univ. of Missouri - Rolla
> EMail:                  Computing Services
> WWW:      SysAdmin:

Rob Hartill.       Internet Movie Database Ltd.

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