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|
-module(timed_cache).
-behavior(gen_server).
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% TYPES %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% EXPORTS %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%% 'gen_server' Exports
-export
(
[
init/1,
handle_cast/2,
handle_call/3, %% No reply will ever be given.
terminate/2,
code_change/3,
format_status/2,
handle_info/2
]
).
%%%% Actual Interface
-export
(
[
fetch/3,
invalidate/3
]
).
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% LOCAL FUNCTIONS %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
add_to_cache (DB, Owner, ObjectID) ->
{ok, TimerPID} = gen_server:start(?MODULE, {DB, {Owner, ObjectID}}, []),
{ok, Data} = database_shim:fetch(DB, ObjectID),
ets:insert(DB, {{Owner, ObjectID}, TimerPID, Data}),
Data.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% EXPORTED FUNCTIONS %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%% 'gen_server' functions
init ({DB, ObjectID}) ->
{ok, {DB, ObjectID}}.
handle_call (invalidate, _, State) ->
{stop, normal, State};
handle_call (ping, _, State) ->
{noreply, State, timed_caches_manager:get_timeout()}.
handle_cast (invalidate, State) ->
{stop, normal, State};
handle_cast (ping, State) ->
{noreply, State, timed_caches_manager:get_timeout()}.
terminate (_, {DB, ObjectID}) ->
io:format
(
"~nCache entry timed out or was invalidated: ~p.~n",
[{DB, ObjectID}]
),
ets:delete(DB, ObjectID).
code_change (_, State, _) ->
{ok, State}.
format_status (_, [_, State]) ->
[{data, [{"State", State}]}].
handle_info(timeout, State) ->
{stop, normal, State};
handle_info(_, {DB, ObjectID}) ->
{noreply, {DB, ObjectID}, timed_caches_manager:get_timeout()}.
%%%% Interface Functions
fetch (DB, Owner, ObjectID) ->
io:format("~nfetch from cache: ~p.~n", [{DB, {Owner, ObjectID}}]),
case ets:lookup(DB, {Owner, ObjectID}) of
[] -> add_to_cache(DB, Owner, ObjectID);
[{_, TimerPID, Data}] ->
gen_server:cast(TimerPID, ping),
Data
end.
invalidate (DB, Owner, ObjectID) ->
case ets:lookup(db, {Owner, ObjectID}) of
[] ->
io:format
(
"~nInvalidation request on non-stored entry: ~p.~n",
[{DB, Owner, ObjectID}]
),
ok;
[{_, TimerPID, _}] ->
io:format
(
"~nInvalidation request on stored entry: ~p.~n",
[{DB, Owner, ObjectID}]
),
gen_server:stop(TimerPID)
end.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% Notes %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
