NAME

CGI::Ex::Recipes::Cache - Naive caching in a database table

SYNOPSIS

Example from CGI::Ex::Recipes::Template::Menu::list_item():

    # ... somewhere at the beginning of a method/subroutine which does heavy computations
    if( $out = $app->cache->get($cache_key) ){ return $out; }
    # ... here are your heavy calculations spread accross many lines
    # making database calls generating HTML etc.
    # ... just before the return of the method
    #try cache support
    $app->cache->set($cache_key, $out);
    return $out;

DESCRIPTION

I found that when I cached in memory some output from CGI::Ex::Recipes::Template::Menu, the performance under mod_perl jumped from:

    ...
    Requests per second:    19.42 [#/sec] (mean)
    Time per request:       154.441 [ms] (mean)
    Time per request:       51.480 [ms] (mean, across all concurrent requests)
    Transfer rate:          67.73 [Kbytes/sec] received

to

    ...
    Requests per second:    42.99 [#/sec] (mean)
    Time per request:       69.792 [ms] (mean)
    Time per request:       23.264 [ms] (mean, across all concurrent requests)
    Transfer rate:          151.74 [Kbytes/sec] received

ApacheBench was invoked like this:

    berov@berovi:~> /opt/apache2/bin/ab -c3  -n300 http://localhost:8081/recipes/index.pl

Of cource this is copied and pasted from my shell. Your results will be different.

I searched CPAN and after realizing that there are too many alternatives I decided to have some fun and write another one -- simple, stupid and naive.

After implementing my naive caching in a database table I have the following results:

    ...
    Requests per second:    58.35 [#/sec] (mean)
    Time per request:       51.418 [ms] (mean)
    Time per request:       17.139 [ms] (mean, across all concurrent requests)
    Transfer rate:          206.74 [Kbytes/sec] received

Not bad, I would say.

NOTE:

    This module is not necessarily compatible with the L<Cache|Cache> interface nor near complete.

METHODS

head2 new

The constructor.

    our $cache_obj = CGI::Ex::Recipes::Cache->new(
        {cache_hash =>\%CACHE_HASH, dbh=>$dbh , expires =>3600*24 }
    );
    Arguments(a hashref):
        cache_hash: Applicaton-wide HASH reference.
                    useful only under mod_perl.
        dbh:        A DBI object.
        expires:    Default expiration for cache entries. Default:time + 3600(one hour)
    Returns:    $self - The cache object used in CGI::Ex::Recipes

exists

    my $bool = $cache->exists('somekey');

Checks for existence of a given key in $self->{cache_hash}. Returns 1 on success, 0 otherwize.

get

    if( $out = $app->cache->get($cache_key) ){ return $out; }

Returns the value of a cache entry. First tries to get it from the $self->{cache_hash} then tries to find it in the databse. If the entry is not available or is expired, returns undef.

set

    $app->cache->set($cache_key, $value [,$expires]);

Inserts a cache entry in the cache database table and returns the result of the operation.

    NOTE:underlying SQL code is currently compatible only with SQLITE and MySQL

The get/set methods DO NOT serialize complex data types. Use freeze/thaw as appropriate.

clear

Clears all entries from the <cache> table and VACUUMS the database. This method should be called immediately after you INSERT or UPDATE something in the database.

    #... in CGI::Ex::Recipes::Edit::finalize
    $self->append_path('view');
    $self->cache->clear;
    return 1;

It is an 'all or nothing' sollution.

freeze

    $app->cache->freze($cache_key, $struct [,$expires]);

Identical to 'set', except that c<$struct> may be any complex data type that will be serialized via Storable.

thaw

    my $struct = $app->cache->thaw($cache_key);

Identical to 'get', except that it will return a complex data type that was set via 'freeze'.

STORING COMPLEX OBJECTS

The set and get methods only allow for working with simple scalar types, but if you want to store more complex types they need to be serialized first. To assist with this, the freeze and thaw methods are provided.

TODO

Generalize the underlying SQL code

SEE ALSO

Cache Cache::Entry

AUTHOR

Красимир Беров, <k.berov at gmail.com>

COPYRIGHT & LICENSE

Copyright 2007 Красимир Беров, all rights reserved.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

cpanm CGI::Ex::Recipes

perl -MCPAN -e shell
install CGI::Ex::Recipes