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% Licensed under the Apache License, Version 2.0 (the "License"); you may not
% use this file except in compliance with the License. You may obtain a copy of
% the License at
%
% http://www.apache.org/licenses/LICENSE-2.0
%
% Unless required by applicable law or agreed to in writing, software
% distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
% WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
% License for the specific language governing permissions and limitations under
% the License.
% todo
% - remove existance check on increment(), decrement() and record(). have
% modules initialize counters on startup.
-module(couch_stats_collector).
-behaviour(gen_server).
-export([init/1, handle_call/3, handle_cast/2, handle_info/2,
terminate/2, code_change/3]).
-export([start/0, stop/0, get/1,
increment/1, decrement/1,
track_process_count/1, track_process_count/2,
record/2, clear/1,
all/0, all/1]).
-record(state, {}).
-define(ABSOLUTE_VALUE_COUNTER_TABLE, abs_table).
-define(HIT_COUNTER_TABLE, hit_table).
% PUBLIC API
start() ->
gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).
stop() ->
gen_server:call(?MODULE, stop).
get(Key) ->
case ets:lookup(?HIT_COUNTER_TABLE, Key) of
[] ->
case ets:lookup(?ABSOLUTE_VALUE_COUNTER_TABLE, Key) of
[] ->
0;
Result2 -> extract_value_from_ets_result(Key, Result2)
end;
[{_,Result1}] -> Result1
end.
increment({Module, Key}) when is_integer(Key) ->
increment({Module, list_to_atom(integer_to_list(Key))});
increment(Key) ->
case catch ets:update_counter(?HIT_COUNTER_TABLE, Key, 1) of
{'EXIT', {badarg, _}} ->
true = ets:insert(?HIT_COUNTER_TABLE, {Key, 1}),
ok;
_ -> ok
end.
decrement(Key) ->
case catch ets:update_counter(?HIT_COUNTER_TABLE, Key, -1) of
{'EXIT', {badarg, _}} ->
true = ets:insert(?HIT_COUNTER_TABLE, {Key, -1}),
ok;
_ -> ok
end.
record(Key, Value) ->
ets:insert(?ABSOLUTE_VALUE_COUNTER_TABLE, {Key, Value}).
clear(Key) ->
true = ets:delete(?ABSOLUTE_VALUE_COUNTER_TABLE, Key).
all() ->
lists:append(ets:tab2list(?HIT_COUNTER_TABLE),
ets:tab2list(?ABSOLUTE_VALUE_COUNTER_TABLE)).
all(Type) ->
case Type of
incremental -> ets:tab2list(?HIT_COUNTER_TABLE);
absolute -> ets:tab2list(?ABSOLUTE_VALUE_COUNTER_TABLE)
end.
track_process_count(Stat) ->
track_process_count(self(), Stat).
track_process_count(Pid, Stat) ->
case (catch couch_stats_collector:increment(Stat)) of
ok ->
spawn(
fun() ->
erlang:monitor(process, Pid),
receive {'DOWN', _, _, _, _} -> ok end,
couch_stats_collector:decrement(Stat)
end);
_ -> ok
end.
% GEN_SERVER
init(_) ->
ets:new(?HIT_COUNTER_TABLE, [named_table, set, public]),
ets:new(?ABSOLUTE_VALUE_COUNTER_TABLE, [named_table, duplicate_bag, public]),
{ok, #state{}}.
handle_call(stop, _, State) ->
{stop, normal, stopped, State}.
% PRIVATE API
extract_value_from_ets_result(_Key, Result) ->
lists:map(fun({_, Value}) -> Value end, Result).
% Unused gen_server behaviour API functions that we need to declare.
%% @doc Unused
handle_cast(foo, State) ->
{noreply, State}.
handle_info(_Info, State) ->
{noreply, State}.
%% @doc Unused
terminate(_Reason, _State) -> ok.
%% @doc Unused
code_change(_OldVersion, State, _Extra) -> {ok, State}.
%% Tests
-ifdef(TEST).
% Internal API unit tests go here
-endif.
|
