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|
-module(timed_cache_object).
-behavior(gen_server).
%%%% 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/2
]
).
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% LOCAL %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
add_to_cache (DB, ObjectID, Timeout) ->
{ok, TimerPID} = gen_server:start(?MODULE, [{DB, ObjectID, Timeout}], []),
Data = nothing, %% Do the actual NoSQL Fetch here.
ets:insert(DB, {ObjectID, TimerPID, Data}),
Data.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% EXPORTED %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%% gen_server
init ({DB, ObjectID, Timeout}) ->
{ok, {DB, ObjectID, Timeout}}.
handle_call (invalidate, _, State) ->
{stop, normal, State};
handle_call (ping, _, {DB, ObjectID, Timeout}) ->
{noreply, {DB, ObjectID, Timeout}, Timeout}.
handle_cast (invalidate, State) ->
{stop, normal, State};
handle_cast (ping, {DB, ObjectID, Timeout}) ->
{noreply, {DB, ObjectID, Timeout}, Timeout}.
terminate (_, {DB, ObjectID, _Timeout}) ->
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, Timeout}) ->
{noreply, {DB, ObjectID, Timeout}, Timeout}.
%%%% interface
fetch (DB, ObjectID, Timeout) ->
case ets:lookup(DB, ObjectID) of
[] -> add_to_cache(DB, ObjectID, Timeout);
[{_, TimerPID, Data}] ->
gen_server:cast(TimerPID, ping),
Data
end.
invalidate (DB, ObjectID) ->
case ets:lookup(DB, ObjectID) of
[] -> ok;
[{_, TimerPID, _}] ->
gen_server:stop(TimerPID)
end.
|
