[Templates] stonehenge.com data/partial HTML caching

[Perrin Harkins]

Randal L. Schwartz wrote:
>       USE mycache = CacheFileCache({
>         namespace => 'stonehenge-nav_stacked_bars',
>         default_expires_in => 1800,
>         auto_purge_interval => 1800,
>       });
>       mykey = [class, instance, global.navbardata.modtime];
>       mykey = mykey.join(":");
>       result = mycache.get(mykey);
>       UNLESS result;
>         result = BLOCK;
>           [[ stuff to compute result deleted ]]
>         END;
>         mycache.set(mykey, result);
>         FILTER stderr; "cache miss on "; mykey; "\n"; END;
>       END;
>       result;

Interesting.  I could add a simple get() option to my cache plugin 
prototype to make it cover this.  Right now you'd have to do it like this:

[% USE cache = Cache %]
[% cache.include(TEMPLATE => nav_bar, CACHE_VARS => ['class', 
'instance', 'global.navbardata.modtime'], TTL => 1800) %]

Your approach of computing the key ahead is more effort in the template, 
but it does solve a problem I had, namely how to resolve multi-level dot 
notation (global.navbardata.modtime) from a plugin at runtime.

Incidentally, I think that a BerkeleyDB backend for Cache::Cache will 
blow away the current file-based one.  Computing the file name is 
surprisingly slow with Digest::SHA1.

- Perrin