[CDBI] Memcached

Randal L. Schwartz merlyn at stonehenge.com
Fri Jan 26 19:28:27 GMT 2007

>>>>> "Derek" == Derek Watson <watson at wayspa.com> writes:

Derek> Can you share your approach and experience? Did you overload
Derek> retrieve() and update()? Did it work as expected?

Sweet was passing data that Cache::FastMmap didn't like, so here's
the top of my database class:

    package INITECH::DB;
    use base Class::DBI::Sweet;
    use strict;

    BEGIN {
      package My::Cache;
      use base qw(Cache::FastMmap);

      sub set {
        my $self = shift;
        my $key = shift;
        my $value = shift;
        ## wrap value, pass it along
        $self->SUPER::set($key, \$value, @_);

      sub get {
        my $self = shift;
        my $key = shift;
        my $value = $self->SUPER::get($key);
        $value = $$value if defined $value;
        return $value;

    BEGIN {
      use File::Temp qw(tempfile);

      our $long_cache = My::Cache->new
        (share_file => "/tmp/initech_db_$<",
         expire_time => 86400,
        ) or die "Cannot create long_cache";
      our ($per_hit_cache_fh, $per_hit_cache_filename) = tempfile();
      our $per_hit_cache = My::Cache->new
        (share_file => $per_hit_cache_filename, # unlinked on program exit
        ) or die "Cannot create per_hit_cache";
      __PACKAGE__->cache($per_hit_cache); # everybody is cached this much
      END { unlink $per_hit_cache_filename }

    sub CACHE_ME {                  # cache me even between hits
      my $class = shift;
      ## warn "enabling cache on $class\n";
      die "value of long_cache is gone" unless our $long_cache;

    __PACKAGE__->connection("dbi:Pg:dbname=blah blah", $user, $pass);

Then each class that wanted to be in the "long" cache (basically,
read-only data) added:

  package INITECH::DB::SomeType;
  use base INITECH::DB;

All other items were cached only per-hit.

Randal L. Schwartz - Stonehenge Consulting Services, Inc. - +1 503 777 0095
<merlyn at stonehenge.com> <URL:http://www.stonehenge.com/merlyn/>
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