| Subject: | same "keys" key/values produce different "cache key" to cache with |
This is likely to be a byproduct of "recent" Perl changes to the "Hash Traversal Randomization", i.e. see http://perldoc.perl.org/perlsec.html#Algorithmic-Complexity-Attacks
The outcome of this is that for the exact same set of "keys" given to the cache, i.e.:
foo_cache.proc('name.tt', ttl => 30, keys => {
foo => 1,
bar => 1,
baz => 1,
});
… Template::Plugin::Cache will create many different "cache keys" internally, i.e. its code:
my $cache_keys = $params->{keys};
$key = join(
':',
(
$params->{template},
map { "$_=$cache_keys->{$_}" } keys %{$cache_keys}
)
);
will produce, given the input above, a $key which is going to be any of:
name.tt:foo=1:bar=1:baz=1
name.tt:foo=1:baz=1:bar=1
name.tt:bar=1:foo=1:baz=1
name.tt:bar=1:baz=1:foo=1
name.tt:baz=1:bar=1:foo=1
name.tt:baz=1:foo=1:bar=1
For users of this caching module, it means that there's no guarantee that the cache _will_ be hit for that exact set of "keys" before the TTL expires.
In the above case, it means that up to six caches will be distinctly created from the same set of unchanging keys, instead of just one.
I guess the fix should be as simple as "adding a sort before that map", i.e.:
my $cache_keys = $params->{keys};
$key = join(
':',
(
$params->{template},
+ sort
map { "$_=$cache_keys->{$_}" } keys %{$cache_keys}
)
);
Hope this helps!
-marco-