On Tue, Mar 27, 2001 at 09:50:33PM +0100, Matt wrote:
> I want to cache some values in my handlers so they don't keep having
> to look stuff up, and so I figured a Cache::SharedMemoryCache would
> be the way to go.
It all depends on what you want to cache and why. If you wanted to
save a trip to the database on each request, a really simple mod_perl
handler could look something like this:
package MyApplication;
use strict;
use Apache::Request;
use Cache::SharedMemoryCache;
sub handler
{
my ( $request );
my $cache = new Cache::SharedMemoryCache( );
my $data = $cache->get( 'data' );
if ( not defined $data )
{
$data = expensive_database_request( );
$cache->set( 'data', $data );
}
$request->content_type( 'text/plain' );
$request->send_http_header( );
$request->print( "data: $data" );
}
The first time this handler is run, the data will not be found in the
cache. The second time, however, the data will be returned from the
cache, saving a trip to the database.
The other question is whether or not to share the cache instance
itself globally. Technically, this is up to you. Personally I
wouldn't bother, considering the overhead of instantiating the cache
is so low that I would rather keep it local to the handler (as I did
above). I tend to only share data globally in mod_perl handlers very
judiciously, and even then I wrap the data in an object that provides
accessor methods. For an example of an object that wraps shared data,
check out Cache::MemoryCache, which simply caches data inside the
process.
Hope this helps a bit. Cheers,
-DeWitt
