./ct_report/coverage/mongoose_instrument.COVER.html

1 -module(mongoose_instrument).
2
3 -behaviour(gen_server).
4
5 %% API
6 -export([start_link/0, persist/0,
7 set_up/1, set_up/3,
8 tear_down/1, tear_down/2,
9 span/4, span/5,
10 execute/3]).
11
12 %% gen_server callbacks
13 -export([init/1, handle_call/3, handle_cast/2, code_change/3, handle_info/2, terminate/2]).
14
15 -ignore_xref([start_link/0, set_up/3, tear_down/2, span/4, span/5, execute/3]).
16
17 -include("mongoose.hrl").
18
19 -type event_name() :: atom().
20 -type labels() :: #{host_type => mongooseim:host_type()}. % to be extended
21 -type metrics() :: #{atom() => spiral | histogram}. % to be extended
22 -type measurements() :: #{atom() => integer() | atom() | binary()}.
23 -type spec() :: {event_name(), labels(), config()}.
24 -type config() :: #{metrics => metrics()}. % to be extended
25 -type handler_fun() :: fun((event_name(), labels(), config(), measurements()) -> any()).
26 -type handlers() :: {[handler_fun()], config()}.
27 -type execution_time() :: integer().
28 -type measure_fun(Result) :: fun((execution_time(), Result) -> measurements()).
29
30 -callback set_up(event_name(), labels(), config()) -> boolean().
31 -callback handle_event(event_name(), labels(), config(), measurements()) -> any().
32
33 -export_type([event_name/0, labels/0, config/0, measurements/0, spec/0, handlers/0]).
34
35 %% API
36
37 -spec start_link() -> gen_server:start_ret().
38 start_link() ->
39 42 gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).
40
41 %% @doc Saves the state to a persistent term, improving performance of `execute' and `span'.
42 %% On the other hand, future calls to `set_up' or `tear_down' will update the persistent term,
43 %% which makes them less performant.
44 %% You should call this function only once - after the initial setup, but before handling any load.
45 -spec persist() -> ok.
46 persist() ->
47 42 gen_server:call(?MODULE, persist).
48
49 %% @doc Sets up instrumentation for multiple events.
50 %% @see set_up/3
51 -spec set_up([spec()]) -> ok.
52 set_up(Specs) ->
53 
:-(
 lists:foreach(fun({EventName, Labels, Config}) -> set_up(EventName, Labels, Config) end, Specs).
54
55 %% @doc Tears down instrumentation for multiple events.
56 %% @see tear_down/2
57 -spec tear_down([spec()]) -> ok.
58 tear_down(Specs) ->
59 
:-(
 lists:foreach(fun({EventName, Labels, _Config}) -> tear_down(EventName, Labels) end, Specs).
60
61 %% @doc Sets up instrumentation for an event identified by `EventName' and `Labels'
62 %% according to `Config'. Fails if the event is already registered, or if the keys of `Labels'
63 %% are different than for already registered events with `EventName'.
64 -spec set_up(event_name(), labels(), config()) -> ok.
65 set_up(EventName, Labels, Config) ->
66 
:-(
 case gen_server:call(?MODULE, {set_up, EventName, Labels, Config}) of
67 
:-(
 ok -> ok;
68 
:-(
 {error, ErrorMap} -> error(ErrorMap)
69 end.
70
71 %% @doc Tears down instrumentation for an event identified by `EventName' and `Labels'.
72 %% This operation is idempotent.
73 -spec tear_down(event_name(), labels()) -> ok.
74 tear_down(EventName, Labels) ->
75 
:-(
 gen_server:call(?MODULE, {tear_down, EventName, Labels}).
76
77 %% @doc Calls `F', measuring its result with `MeasureF', and calls attached event handlers.
78 %% @see span/5
79 -spec span(event_name(), labels(), fun(() -> Result), measure_fun(Result)) -> Result.
80 span(EventName, Labels, F, MeasureF) ->
81 
:-(
 span(EventName, Labels, F, [], MeasureF).
82
83 %% @doc Calls `F' with `Args', measuring its execution time.
84 %% The time and the result are passed to `MeasureF', which returns measurements.
85 %% The measurements are then passed to all handlers attached to
86 %% the event identified by `EventName' and `Labels'.
87 %% Fails without calling `F' if the event is not registered.
88 -spec span(event_name(), labels(), fun((...) -> Result), list(), measure_fun(Result)) -> Result.
89 span(EventName, Labels, F, Args, MeasureF) ->
90 
:-(
 Handlers = get_handlers(EventName, Labels),
91 
:-(
 {Time, Result} = timer:tc(F, Args),
92 
:-(
 handle_event(EventName, Labels, MeasureF(Time, Result), Handlers),
93 
:-(
 Result.
94
95 %% @doc Executes all handlers attached to the event identified by `EventName' and `Labels',
96 %% passing `Measurements' to them. Fails if the event is not registered.
97 -spec execute(event_name(), labels(), measurements()) -> ok.
98 execute(EventName, Labels, Measurements) ->
99 
:-(
 Handlers = get_handlers(EventName, Labels),
100 
:-(
 handle_event(EventName, Labels, Measurements, Handlers).
101
102 %% gen_server callbacks
103
104 -type state() :: #{event_name() => #{labels() => handlers()}}.
105
106 -spec init([]) -> {ok, state()}.
107 init([]) ->
108 42 erlang:process_flag(trap_exit, true), % Make sure that terminate is called
109 42 persistent_term:erase(?MODULE), % Prevent inconsistency when restarted after a kill
110 42 {ok, #{}}.
111
112 -spec handle_call(any(), gen_server:from(), state()) ->
113 {reply, ok | {ok, handlers()} | {error, map()}, state()}.
114 handle_call({set_up, EventName, Labels, Config}, _From, State) ->
115 
:-(
 case set_up_and_register(EventName, Labels, Config, State) of
116 {error, _} = Error ->
117 
:-(
 {reply, Error, State};
118 NewState = #{} ->
119 
:-(
 update_if_persisted(State, NewState),
120 
:-(
 {reply, ok, NewState}
121 end;
122 handle_call({tear_down, EventName, Labels}, _From, State) ->
123 
:-(
 NewState = deregister(EventName, Labels, State),
124 
:-(
 update_if_persisted(State, NewState),
125 
:-(
 {reply, ok, NewState};
126 handle_call(persist, _From, State) ->
127 42 persistent_term:put(?MODULE, State),
128 42 {reply, ok, State};
129 handle_call({lookup, EventName, Labels}, _From, State) ->
130 
:-(
 {reply, lookup(EventName, Labels, State), State};
131 handle_call(Request, From, State) ->
132 
:-(
 ?UNEXPECTED_CALL(Request, From),
133 
:-(
 {reply, {error, #{what => unexpected_call, request => Request}}, State}.
134
135 -spec handle_cast(any(), state()) -> {noreply, state()}.
136 handle_cast(Msg, State) ->
137 
:-(
 ?UNEXPECTED_CAST(Msg),
138 
:-(
 {noreply, State}.
139
140 -spec handle_info(any(), state()) -> {noreply, state()}.
141 handle_info(Info, State) ->
142 
:-(
 ?UNEXPECTED_INFO(Info),
143 
:-(
 {noreply, State}.
144
145 -spec terminate(any(), state()) -> ok.
146 terminate(_Reason, _State) ->
147 42 persistent_term:erase(?MODULE),
148 42 ok.
149
150 -spec code_change(any(), state(), any()) -> {ok, state()}.
151 code_change(_OldVsn, State, _Extra) ->
152 
:-(
 {ok, State}.
153
154 %% Internal functions
155
156 -spec update_if_persisted(state(), state()) -> ok.
157 update_if_persisted(State, NewState) ->
158 
:-(
 try persistent_term:get(?MODULE) of
159 
:-(
 State -> persistent_term:put(?MODULE, NewState)
160 catch
161 
:-(
 error:badarg -> ok
162 end.
163
164 -spec set_up_and_register(event_name(), labels(), config(), state()) -> state() | {error, map()}.
165 set_up_and_register(EventName, Labels, Config, State) ->
166 
:-(
 LabelKeys = label_keys(Labels),
167 
:-(
 case State of
168 #{EventName := #{Labels := _}} ->
169 
:-(
 {error, #{what => event_already_registered,
170 event_name => EventName, labels => Labels}};
171 #{EventName := HandlerMap} ->
172 
:-(
 {ExistingLabels, _, _} = maps:next(maps:iterator(HandlerMap)),
173 
:-(
 case label_keys(ExistingLabels) of
174 LabelKeys ->
175 
:-(
 Handlers = do_set_up(EventName, Labels, Config),
176 
:-(
 State#{EventName := HandlerMap#{Labels => Handlers}};
177 ExistingKeys ->
178 
:-(
 {error, #{what => inconsistent_labels,
179 event_name => EventName, labels => Labels,
180 existing_label_keys => ExistingKeys}}
181 end;
182 #{} ->
183 
:-(
 Handlers = do_set_up(EventName, Labels, Config),
184 
:-(
 State#{EventName => #{Labels => Handlers}}
185 end.
186
187 -spec do_set_up(event_name(), labels(), config()) -> handlers().
188 do_set_up(EventName, Labels, Config) ->
189 
:-(
 AllModules = handler_modules(),
190 
:-(
 UsedModules = lists:filter(fun(Mod) -> Mod:set_up(EventName, Labels, Config) end, AllModules),
191 
:-(
 {[fun Mod:handle_event/4 || Mod <- UsedModules], Config}.
192
193 -spec deregister(event_name(), labels(), state()) -> state().
194 deregister(EventName, Labels, State) ->
195 
:-(
 case State of
196 #{EventName := HandlerMap} ->
197 
:-(
 case maps:remove(Labels, HandlerMap) of
198 Empty when Empty =:= #{} ->
199 
:-(
 maps:remove(EventName, State);
200 NewHandlerMap ->
201 
:-(
 State#{EventName := NewHandlerMap}
202 end;
203 #{} ->
204 
:-(
 State
205 end.
206
207 -spec lookup(event_name(), labels()) -> {ok, handlers()} | {error, map()}.
208 lookup(EventName, Labels) ->
209 
:-(
 try persistent_term:get(?MODULE) of
210 State ->
211 
:-(
 lookup(EventName, Labels, State)
212 catch
213 %% Although persist/0 should be called before handling traffic,
214 %% some instrumented events might happen before that, and they shouldn't fail.
215 error:badarg ->
216 
:-(
 ?LOG_INFO(#{what => mongoose_instrument_lookup_without_persistent_term,
217 
:-(
 event_name => EventName, Labels => Labels}),
218 
:-(
 gen_server:call(?MODULE, {lookup, EventName, Labels})
219 end.
220
221 -spec lookup(event_name(), labels(), state()) -> {ok, handlers()} | {error, map()}.
222 lookup(EventName, Labels, State) ->
223 
:-(
 case State of
224 #{EventName := #{Labels := Handlers}} ->
225 
:-(
 {ok, Handlers};
226 #{} ->
227 
:-(
 {error, #{what => event_not_registered, event_name => EventName, labels => Labels}}
228 end.
229
230 -spec label_keys(labels()) -> [atom()].
231 label_keys(Labels) ->
232 
:-(
 lists:sort(maps:keys(Labels)).
233
234 -spec get_handlers(event_name(), labels()) -> handlers().
235 get_handlers(EventName, Labels) ->
236 
:-(
 case lookup(EventName, Labels) of
237 
:-(
 {ok, Handlers} -> Handlers;
238 
:-(
 {error, ErrorMap} -> error(ErrorMap)
239 end.
240
241 -spec handle_event(event_name(), labels(), measurements(), handlers()) -> ok.
242 handle_event(Event, Labels, Measurements, {EventHandlers, Config}) ->
243 
:-(
 lists:foreach(fun(Handler) -> Handler(Event, Labels, Config, Measurements) end, EventHandlers).
244
245 -spec handler_modules() -> [module()].
246 handler_modules() ->
247 
:-(
 [list_to_existing_atom("mongoose_instrument_" ++ atom_to_list(Key))
248 
:-(
 || Key <- maps:keys(mongoose_config:get_opt(instrumentation))].
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