Hi Bill,
I'm replying because I didn't see you getting a response in a few days.
On Mon, 9 Apr 2012 17:04:38 +0800
Bill Moseley <mose...@hank.org> wrote:
> We have an in-house storage "backend" we use for a number of purposes. We
> can pretend it's something like memcached that is configured with host
> names. I have a role for working with this backend which is consumed by a
> number of more specific classes. For example, each specific class handles
> decoding and encoding the stored data.
>
> Often a given application will use a number of these specific classes. I
> want to use a shared connection in this case. So, instead of a singleton
> backend class, I want a singleton cached by the config (by the hosts in
> this example).
>
>
> my $foo_store = My::Store::Foo->new( { hosts => \@hosts } );
> my $bar_store = My::Store::Bar->new( { hosts => \@hosts } );
>
>
> So, $foo_store->backend_connection = $foo_store->backend_connection because
> @hosts are the same in both.
>
>
> What I've been doing is something like this in my role:
>
> has backend_connection => ( builder => _build_connection );
>
>
> my %cached_connections;
>
> sub _build_connection {
> my $self = shift;
> return $cached_connection{ $self->connection_key } ||=
> $self->new_connection;
> }
>
> sub connection_key { return join ':', shift->host_list }
>
>
> Does this seem like a reasonable approach?
>
Yes, pretty much. Maybe I would also make sure that ->host_list is sorted and
uniq’ed or otherwise mostly lacking silly permutations and variations that can
interfere with the caching.
Furthermore, what I normally like to do to implement singletons is create an
"environment" object that contains all the common data, and keep a reference to
it for every class in the system. This way, one can have more than one
environment in the program.
Regards,
Shlomi Fish
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