Hi
Neil Gunton wrote:
Well, that seemed to do the trick! So the caveat seems to be: Be
careful using both mod_deflate and mod_cache (mod_disk_cache
specifically) together if you have a large dynamic website that can
generate a large number of distinct pages. Mod_deflate produces a
This is probably a digression from your discussion, but I'm not sure if
any of you have used gzip + md5sum together before. I have, and it can
be annoying especially if you are playing with large data files like I
do. This is because gzip seems to (not 100% sure) store some time
information in the archive. So, if you create two archives of the same
files, they aren't identical...their md5sums do not match.
As deflate is essentially the same algorithm as gzip, it is somewhat the
same annoyance...
Web pages seem to render a little faster in the browser too. That may
be my imagination and/or placebo effect, but it might make sense if
there isn't that additional compression/decompression going on both ends.
The only downside is that people on extremely slow dialup connections
might notice longer download times for page text... but I have to
wonder if that's really an issue today. Back in 1998 perhaps you might
care about something being 20KB rather than 80KB, but surely not
today. In any case, don't dialup ISPs often implement their own
compression now?
I had looked at the effect compression has on web pages a while ago.
Though not relevant to modperl, there is obviously a cost to compression
and since most HTML pages are small, sometimes it is hard to justify.
If users are downloading XML files of data, though, then that is of
course worth it...but one could argue that if you are making XML files
available for download, then wouldn't it be better to compress it
yourself rather than asking Apache to compress on-the-fly.
As for dialup, if I remember from those dark modem days :-), even many
of them had compression built in. In fact, I think they had some form
of the deflate/gzip/sliding window algorithm. And for those of us who
have tried gzipping an already-gzipped file, adding compression to
something that is already compressed is generally counter-productive...
Anyway, I don't think it is much of an issue...might be more helpful to
educate web page creators to not put MBs of images on a single page. :-)
Ray
Anyway, hope that's helpful to anybody running large dynamic websites
behind a reverse proxy. Keep mod_cache, maybe think about ditching
mod_deflate. The combination does technically work, but for large
numbers of pages, it can make your cache size (and your iowait) explode.
