add support for callback functions around worker initialisation

src/wpool_process.erl

@@ -76,9 +76,12 @@ cast_call(Process, From, Call) ->
 %% @private
 -spec init({atom(), atom(), term(), [wpool:option()]}) -> {ok, state()}.
 init({Name, Mod, InitArgs, Options}) ->
+  wpool_worker_callbacks:call(on_init_start, Options, [Name]),
+
   case Mod:init(InitArgs) of
     {ok, ModState} ->
       ok = wpool_utils:notify_queue_manager(new_worker, Name, Options),
+      wpool_worker_callbacks:call(on_new_worker, Options, [Name]),
       {ok, #state{ name = Name
                  , mod = Mod
                  , state = ModState
@@ -210,3 +213,5 @@ handle_call(Call, From, State) ->
                                     , State#state.name
                                     , State#state.options),
   Reply.
+
+

test/wpool_SUITE.erl

@@ -34,13 +34,14 @@
         , default_options/1
         , complete_coverage/1
         , broadcast/1
+        , worker_callbacks/1
         ]).
 
 -spec all() -> [atom()].
 all() ->
   [too_much_overrun, overrun, stop_pool, non_brutal_shutdown, stats,
    default_strategy, default_options, complete_coverage, broadcast,
-   kill_on_overrun].
+   kill_on_overrun, worker_callbacks].
 
 -spec init_per_suite(config()) -> config().
 init_per_suite(Config) ->
@@ -370,6 +371,23 @@ broadcast(_Config) ->
   meck:unload(x),
   {comment, []}.
 
+-spec worker_callbacks(config) -> ok.
+worker_callbacks(_Config) ->
+  Pool = callbacks_test,
+  WorkersCount = 13,
+  meck:new(callbacks, [non_strict]),
+  meck:expect(callbacks, on_init_start, fun(_APoolName) -> ok end),
+  meck:expect(callbacks, on_new_worker, fun(_APoolName) -> ok end),
+  {ok, _Pid} = wpool:start_pool(Pool, [{workers, WorkersCount},
+                                       {callbacks, #{on_init_start =>
+                                                     fun callbacks:on_init_start/1,
+                                                    on_new_worker =>
+                                                     fun callbacks:on_new_worker/1}}]),
+  WorkersCount = meck:num_calls(callbacks, on_init_start, ['_']),
+  WorkersCount = meck:num_calls(callbacks, on_new_worker, ['_']),
+
+  ok.
+
 
 %% =============================================================================
 %% Helpers