CGI::Cache 1.4200

CGI::Cache is a Perl extension to help cache output of time-intensive CGI scripts.

WARNING

The interface as of version 1.01 has changed considerably and is NOT compatible with earlier versions. A smaller interface change also occurred in version 1.20.

SYNOPSIS

Heres a simple example:

#!/usr/bin/perl

use CGI;
use CGI::Cache;

# Set up cache
CGI::Cache::setup();

my $cgi = new CGI;

# CGI::Vars requires CGI version 2.50 or better
CGI::Cache::set_key($cgi->Vars);

# This should short-circuit the rest of the loop if a cache value is
# already there
CGI::Cache::start() or exit;

print $cgi->header, "n";

print << EOF;
< html >< body >
< p >

This prints to STDOUT, which will be cached.
If the next visit is within 24 hours, the cached STDOUT
will be served instead of executing this print.

< /body >< /html >

EOF

Heres a more complex example:

use CGI;
use CGI::Cache;

my $query = new CGI;

# Set up a cache in /tmp/CGI_Cache/demo_cgi, with publicly
# unreadable cache entries, a maximum size of 20 megabytes,
# and a time-to-live of 6 hours.
CGI::Cache::setup( { cache_options =>
{ cache_root => /tmp/CGI_Cache,
namespace => demo_cgi,
directory_umask => 077,
max_size => 20 * 1024 * 1024,
default_expires_in => 6 hours,
}
} );

# CGI::Vars requires CGI version 2.50 or better
CGI::Cache::set_key( $query->Vars );
CGI::Cache::invalidate_cache_entry()
if $query->param( force_regenerate ) eq true;
CGI::Cache::start() or exit;

print "Content-type: text/htmlnn";

print << EOF;
< html >< body >
< p >

This prints to STDOUT, which will be cached.
If the next visit is within 6 hours, the cached STDOUT
will be served instead of executing these prints.
< /p >
EOF

CGI::Cache::pause();

print <<EOF;

This is not cached.

EOF

CGI::Cache::continue();

print <<EOF;
< /body >< /html >
EOF

# Optional unless youre using mod_perl for FastCGI
CGI::Cache::stop();

This module is intended to be used in a CGI script that may benefit from caching its output. Some CGI scripts may take longer to execute because the data needed in order to construct the page may not be quickly computed. Such a script may need to query a remote database, or may rely on data that doesnt arrive in a timely fashion, or it may just be computationally intensive. Nonetheless, if you can afford the tradeoff of showing older, cached data vs. CGI execution time, then this module will perform that function.

This module was written such that any existing CGI code could benefit from caching without really changing any of existing CGI code guts. The CGI script can do just what it has always done, that is, construct an html page and print it to the output file descriptor, then exit. What youll do in order to cache pages is include the module, specify some cache options and the cache key, and then call start() to begin caching output.

Internally, the CGI::Cache module ties the output file descriptor (usually STDOUT) to an internal variable to which all output is saved. When the user calls stop() (or the END{} block of CGI::Cache is executed during script shutdown) the contents of the variable are inserted into the cache using the cache key the user specified earlier with set_key().

Once a page has been cached in this fashion, a subsequent visit to that page will invoke the start() function again, which will then check for an existing cache entry for the given key before continuing through the code. If the cache entry exists, then the cache entrys content is printed to the output filehandle (usually STDOUT) and a 0 is returned to indicate that cached output was used.