proc monitor module

src/emqttd_pmon.erl

@@ -0,0 +1,50 @@
+%%--------------------------------------------------------------------
+%% Copyright (c) 2016 Feng Lee <feng@emqtt.io>. All Rights Reserved.
+%%
+%% 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.
+%%--------------------------------------------------------------------
+
+-module(emqttd_pmon).
+
+-author("Feng Lee <feng@emqtt.io>").
+
+-type(pmon() :: {?MODULE, map()}).
+
+-export([new/0, monitor/2, demonitor/2, erase/2]).
+
+new() -> {?MODULE, [maps:new()]}.
+
+-spec(monitor(pid(), pmon()) -> pmon()).
+monitor(Pid, PM = {?MODULE, [M]}) ->
+    case maps:is_key(Pid, M) of
+        true ->
+            PM;
+        false ->
+            Ref = erlang:monitor(process, Pid),
+            {?MODULE, [maps:put(Pid, Ref, M)]}
+    end.
+
+-spec(demonitor(pid(), pmon()) -> pmon()).
+demonitor(Pid, PM = {?MODULE, [M]}) ->
+    case maps:find(Pid, M) of
+        {ok, Ref} ->
+            erlang:demonitor(Ref, [flush]),
+            {?MODULE, [maps:remove(Pid, M)]};
+        error ->
+            PM
+    end.
+
+-spec(erase(pid(), pmon()) -> pmon()).
+erase(Pid, {?MODULE, [M]}) ->
+    {?MODULE, [maps:remove(Pid, M)]}.
+