pereinar 2002/10/31 01:20:03
Modified: src/docs/tutorials Changes.pod config.cfg
Added: src/docs/tutorials/client/compression compression.pod
Log:
Added Web Content Compression FAQ by Slava.
Submitted by: "Slava Bizyayev" <[EMAIL PROTECTED]>
Reviewed by: Per Einar, Ged Haywood
Revision Changes Path
1.6 +5 -0 modperl-docs/src/docs/tutorials/Changes.pod
Index: Changes.pod
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RCS file: /home/cvs/modperl-docs/src/docs/tutorials/Changes.pod,v
retrieving revision 1.5
retrieving revision 1.6
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+++ Changes.pod 31 Oct 2002 09:20:03 -0000 1.6
@@ -9,6 +9,11 @@
The most recent changes are listed first.
+=head1 Ongoing
+
+* Added "Web Content Compression FAQ" by Slava Bizyayev E<lt>slava
+ at) cpan.orgE<gt>
+
=head1 Wed Jun 5 19:24:05 CET 2002
* Re-arranged content completely to better classify and be able to
1.8 +1 -0 modperl-docs/src/docs/tutorials/config.cfg
Index: config.cfg
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RCS file: /home/cvs/modperl-docs/src/docs/tutorials/config.cfg,v
retrieving revision 1.7
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group => 'Client side facts and bugs',
chapters => [qw(
client/browserbugs/browserbugs.pod
+ client/compression/compression.pod
)],
changes => 'Changes.pod',
1.1
modperl-docs/src/docs/tutorials/client/compression/compression.pod
Index: compression.pod
===================================================================
=head1 NAME
Web Content Compression FAQ
=head1 Description
Compression of outgoing traffic from web servers is beneficial for
clients, who get quicker responses, as well as for providers who use
less bandwith. Many solutions exist for mod_perl and Apache, and we
discuss some of the aspects involved here.
This FAQ is written mainly for Internet content provider management
familiar with Internet traffic issues and network equipment and its
cost. This document may also be informative for ISP system
administrators and webmasters seeking to improve throughput and
bandwidth efficiency.
=head1 Q: Why it is important to compress web content?
=head2 A: Reduced equipment costs and the competitive advantage of
dramatically faster page loads.
Web content compression noticeably increases delivery speed to clients
and may allow providers to serve higher content volumes without
increasing hardware expenditures. It visibly reduces actual content
download time, a benefit most apparent to users of dialup and
high-traffic connections.
=head1 Q: How much improvement can I expect?
=head2 A: Effective compression can achieve increases in transmission
efficiency from 3 to 20 times.
The compression ratio is highly content-dependent. For example, if
the compression algorithm is able to detect repeated patterns of
characters, compression will be greater than if no such patterns
exist. You can usually expect to realize an improvement between of 3
to 20 times on regular HTML, JavaScript, and other ASCII content. I
have seen peak HTML file compression improvements in excess of more
than 200 times, but such occurrences are infrequent. On the other
hand I have never seen ratios of less than 2.5 times on text/HTML
files. Image files normally employ their own compression techniques
that reduce the advantage of further compression.
=for html
<blockquote>
On May 21, 2002 Peter J. Cranstone wrote to the
[EMAIL PROTECTED] mailing list:
I<"...With 98% of the world on a dial up modem, all they care about is
how long it takes to download a page. It doesn't matter if it
consumes a few more CPU cycles if the customer is happy. It's cheaper
to buy a newer faster box, than it is to acquire new customers.">
=for html
</blockquote>
=head1 Q: How hard is it to implement content compression on an existing site?
=head2 A: Implementing content compression on an existing site
typically involves no more that installing and configuring an
appropriate Apache handler on the Web server.
This approach works in most of the cases I have seen. In some special
cases you will need to take extra care with respect to the global
architecture of your web application, but such cases may generally be
readily addressed through various techniques. To date I have found no
fundamental barriers to practical implementation of Web content
compression.
=head1 Q: Does compression work with standard Web browsers?
=head2 A: Yes. No client side changes or settings are required.
All modern browser makers claim to be able to handle compressed
content and are able to decompress it on the fly, transparent to the
user. There are some known bugs in some old browsers, but these can
be taken into account through appropriate configuration of the Web
server.
=head1 Q: What software is required on the server side?
=head2 A: There are six known modules/packages for the Web content
compression available to date for Apache (in alphabetical order):
=over 4
=item * Apache::Compress
a mod_perl handler developed by Ken Williams (U.S.) which compresses
output through C<Apache::Filter>
=item * Apache::Dynagzip
a family of mod_perl handlers, developed by Slava Bizyayev -- a
Russian programmer residing in the U.S.
=item * Apache::Gzip
an example of mod_perl filter developed by Lincoln Stein and Doug
MacEachern for their book I<Writing Apache Modules with Perl and C>
(U.S.), which like C<Apache::Compress> works with C<Apache::Filter>.
=item * Apache::GzipChain
a mod_perl handler developed by Andreas Koenig (Germany), which
compresses output through C<Apache::OutputChain>.
=item * mod_deflate
an Apache handler written in C by Igor Sysoev (Russia).
=item * mod_gzip
an Apache handler written in C. Original author: Kevin Kiley, I<Remote
Communications, Inc.> (U.S.)
=back
In February 2002, Nicholas Oxhøj wrote to the modperl@apache.org
mailing list about his own experience to find the appropriate Apache
gzipping tool for streaming outbound content:
=for html <blockquote>
I<"... I have been experimenting with all the different Apache
compression modules I have been able to find, but have not been able
to get the desired result. I have tried C<Apache::GzipChain>,
C<Apache::Compress>, C<mod_gzip> and C<mod_deflate>, with different
results. One I cannot get to work at all. Most work, but seem to
collect all the output before compressing it and sending it to the
browser...>
I<... Wouldn't it be nice to have some option to specify that the
handler should flush and send the currently compressed output every
time it had received a certain amount of input or every time it had
generated a certain amount of output?..>
I<... So I am basically looking for anyone who has had any success in
achieving this kind of "streaming" compression, who could direct me at
an appropriate Apache module.">
=for html
</blockquote>
The C<Apache::Dynagzip> package wasn't publicly available at that
time.
=head1 Analysis of different packages
=head2 Apache::DynaGzip
C<Apache::Dynagzip> is most useful when one needs to compress dynamic
outbound Web content (generated on the fly from databases, XML, etc.)
when content length is not known at the time of the request.
C<Apache::Dynagzip>'s features include:
=over 4
=item * Support for both HTTP/1.0 and HTTP/1.1.
=item * Control over the chunk size on HTTP/1.1 for on-the-fly content
compression.
=item * Support for any Perl, Java, or C/C++ CGI applications.
=item * Advanced control over the proxy cache with the C<Vary> HTTP header.
=item * Optional control over content lifetime in the client's local
cache with the C<Expires> HTTP header.
=item * Optional extra-light compression
(removal of leading blank spaces and/or blank lines), which works for all
browsers,
including older ones that cannot uncompress gzip format.
=item * Optional support for server-side caching of the dynamically
generated (and compressed) content.
=back
=head1 Maintainers
The maintainer is the person you should contact with updates,
corrections and patches.
=over
=item *
Slava Bizyayev E<lt>slava (at) cpan.orgE<gt>
=back
=head1 Authors
=over
=item *
Slava Bizyayev E<lt>slava (at) cpan.orgE<gt>
=back
Only the major authors are listed above. For contributors see the
Changes file.
=cut
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