Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

Can someone tell me what I'm doing wrong? 
#!/usr/bin/perl -w

use Cache::MemoryCache;

my $cache = new Cache::MemoryCache();
my $customer = $cache->get($ARGV[0]);

if( not defined $customer ){
    print "setting cache\n";
    $customer->{'email_address'} = 'foo@foo.com';
    $customer->{'first_name'} = 'foo';
    $customer->{'last_name'} = 'bar';
    $customer->{'id'} = $ARGV[0];
    $cache->set($ARGV[0], $customer, "10 minutes" );
}

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For some reason I can get the FileCache to work but not the memory Cache. This works just fine in the "Default" Namespace 
#!/usr/bin/perl -w

use Cache::FileCache;

my $cache = new Cache::FileCache();
my $customer = $cache->get($ARGV[0]);

if( not defined $customer ){
    print "setting cache\n";
    $customer->{'email_address'} = 'foo@foo.com';
    $customer->{'first_name'} = 'foo';
    $customer->{'last_name'} = 'bar';
    $customer->{'id'} = $ARGV[0];
    $cache->set($ARGV[0], $customer, "10 minutes" );
}

[download]

Replies are listed 'Best First'.
Re: Cache::MemoryCache
by diotalevi (Canon) on Jul 19, 2003 at 00:31 UTC

    What do you mean by "it doesn't work"? The memory cache goes away when the perl program exits. For your example the cache is *always* empty when the script starts. You have to use a FileCache or something similar if you want it to keep its data between calls to your program.

[reply]
Re: Cache::MemoryCache
by sauoq (Abbot) on Jul 19, 2003 at 00:34 UTC

    FileCache is persistent across processes. MemoryCache isn't.

    -sauoq
"My two cents aren't worth a dime.";
[reply]
      Is there a way for me to make it persistent? I want to hit the db, populate the object and cache it in memory and avoid having to hit the db again, next time I have a request for that object.
[reply]

        maybe, just maybe you can use Cache::SharedMemoryCache

        have one program that that stays running to hold the cache in memory while other programs come and go.

        
# holdcache.pl

use Cache::SharedMemoryCache;
my %cache_options_= (
  'namespace' => 'MyNamespace',
);
my $c = Cache::SharedMemoryCache->new( \%cache_options )
  or die( "Couldn't instantiate SharedMemoryCache" );

while (1) { sleep 300; }

__END__

        [download]

        should do to keep the cache open.

        $ perl holdcache.pl &

$ perl -e 'use Cache::SharedMemoryCache;$c=Cache::SharedMemoryCache->n
+ew({namespace=>"MyNamespace"}) or die;$c->set("foo",1);'

$ perl -e 'use Cache::SharedMemoryCache;$c=Cache::SharedMemoryCache->n
+ew({namespace=>"MyNamespace"}) or die;$x=$c->get("foo");print $x,$/'
1

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        presto!

[reply]
[d/l]
[select]

        Use FileCache, then its persistent.

[reply]
        Is there a way for me to make it persistent?

        Uh... no. You could get a close approximation by using FileCache and a RAM disk.

        -sauoq
"My two cents aren't worth a dime.";
[reply]
Re: Cache::MemoryCache
by fglock (Vicar) on Jul 19, 2003 at 02:46 UTC

    You can use a two level cache.

    #!/usr/bin/perl -w
use Cache::MemoryCache;
use Cache::FileCache;
my $file_cache = new Cache::FileCache();
my $mem_cache = new Cache::MemoryCache();

my $customer = $mem_cache->get($ARGV[0]);
if( not defined $customer ){

 $customer = $file_cache->get($ARGV[0]);
 if( not defined $customer ){

    print "setting cache\n";
    $customer->{'email_address'} = 'foo@foo.com';
    $customer->{'first_name'} = 'foo';
    $customer->{'last_name'} = 'bar';
    $customer->{'id'} = $ARGV[0];
    $file_cache->set($ARGV[0], $customer, "10 minutes" );
  }
  $mem_cache->set($ARGV[0], $customer, "10 minutes" );
}

    [download]

    Note: untested, and may contain logic errors.

[reply]
[d/l]

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