Merge pull request #1372 from pguyot/w47/improve-supervisor

Extend support of `supervisor` module

Add `supervisor:start_child/2`
Add map syntax for supervisor init callback

These changes are made under both the "Apache 2.0" and the "GNU Lesser General
Public License 2.1 or later" license terms (dual license).

SPDX-License-Identifier: Apache-2.0 OR LGPL-2.1-or-later

Author: bettio

libs/estdlib/src/supervisor.erl

@@ -23,7 +23,9 @@
 -behavior(gen_server).
 
 -export([
-    start_link/2, start_link/3
+    start_link/2,
+    start_link/3,
+    start_child/2
 ]).
 
 -export([
@@ -33,63 +35,138 @@
     handle_info/2
 ]).
 
--record(child, {pid = undefined, id, mfargs, restart_type, shutdown, child_type, modules = []}).
--record(state, {children = []}).
+-export_type([
+    child_spec/0,
+    strategy/0,
+    sup_flags/0
+]).
+
+-type restart() :: permanent | transient | temporary.
+-type shutdown() :: brutal_kill | timeout().
+-type child_type() :: worker | supervisor.
+
+-type strategy() :: one_for_all | one_for_one.
+-type sup_flags() ::
+    #{
+        strategy => strategy(),
+        intensity => non_neg_integer(),
+        period => pos_integer()
+    }
+    | {RestartStrategy :: strategy(), Intensity :: non_neg_integer(), Period :: pos_integer()}.
+
+-type child_spec() ::
+    #{
+        id := any(),
+        start := {module(), atom(), [any()]},
+        restart => restart(),
+        shutdown => shutdown(),
+        type => child_type(),
+        modules => [module()] | dynamic
+    }
+    | {
+        Id :: any(),
+        StartFunc :: {module(), atom(), [any()]},
+        Restart :: restart(),
+        Shutdown :: shutdown(),
+        Type :: child_type(),
+        Modules :: [module()] | dynamic
+    }.
+
+-record(child, {
+    pid = undefined,
+    id :: any(),
+    start :: {module(), atom(), [any()] | undefined},
+    restart :: restart(),
+    shutdown :: shutdown(),
+    type :: child_type
+}).
+-record(state, {restart_strategy :: strategy(), children = [] :: [#child{}]}).
 
 start_link(Module, Args) ->
     gen_server:start_link(?MODULE, {Module, Args}, []).
 start_link(SupName, Module, Args) ->
     gen_server:start_link(SupName, ?MODULE, {Module, Args}, []).
 
+start_child(Supervisor, ChildSpec) ->
+    gen_server:call(Supervisor, {start_child, ChildSpec}).
+
 init({Mod, Args}) ->
     erlang:process_flag(trap_exit, true),
     case Mod:init(Args) of
-        {ok, {{one_for_one, _Intensity, _Period}, StartSpec}} ->
-            State = init_state(StartSpec, #state{}),
+        {ok, {{Strategy, _Intensity, _Period}, StartSpec}} ->
+            State = init_state(StartSpec, #state{restart_strategy = Strategy}),
+            NewChildren = start_children(State#state.children, []),
+            {ok, State#state{children = NewChildren}};
+        {ok, {#{strategy := Strategy}, StartSpec}} ->
+            State = init_state(StartSpec, #state{restart_strategy = Strategy}),
             NewChildren = start_children(State#state.children, []),
             {ok, State#state{children = NewChildren}};
         Error ->
             {stop, {bad_return, {mod, init, Error}}}
     end.
 
-init_state([{ChildId, MFA, Restart, brutal_kill, Type, Modules} | T], State) ->
-    Child = #child{
+-spec child_spec_to_record(child_spec()) -> #child{}.
+child_spec_to_record({ChildId, MFA, Restart, Shutdown, Type, _Modules}) ->
+    #child{
+        id = ChildId,
+        start = MFA,
+        restart = Restart,
+        shutdown = Shutdown,
+        type = Type
+    };
+child_spec_to_record(#{id := ChildId, start := MFA} = ChildMap) ->
+    Restart = maps:get(restart, ChildMap, permanent),
+    Type = maps:get(type, ChildMap, worker),
+    Shutdown = maps:get(
+        shutdown,
+        ChildMap,
+        case Type of
+            worker -> 5000;
+            supervisor -> infinity
+        end
+    ),
+    #child{
         id = ChildId,
-        mfargs = MFA,
-        restart_type = Restart,
-        shutdown = brutal_kill,
-        child_type = Type,
-        modules = Modules
-    },
+        start = MFA,
+        restart = Restart,
+        shutdown = Shutdown,
+        type = Type
+    }.
+
+init_state([ChildSpec | T], State) ->
+    Child = child_spec_to_record(ChildSpec),
     NewChildren = [Child | State#state.children],
     init_state(T, #state{children = NewChildren});
 init_state([], State) ->
     State#state{children = lists:reverse(State#state.children)}.
 
 start_children([Child | T], StartedC) ->
-    #child{mfargs = {M, F, Args}} = Child,
-    case apply(M, F, Args) of
-        {ok, Pid} when is_pid(Pid) ->
+    case try_start(Child) of
+        {ok, Pid, _Result} ->
             start_children(T, [Child#child{pid = Pid} | StartedC])
     end;
 start_children([], StartedC) ->
     StartedC.
 
 restart_child(Pid, Reason, State) ->
-    Child = lists:keyfind(Pid, #child.pid, State#state.children),
-
-    #child{mfargs = {M, F, Args}} = Child,
-    case should_restart(Reason, Child#child.restart_type) of
-        true ->
-            case apply(M, F, Args) of
-                {ok, NewPid} when is_pid(Pid) ->
-                    NewChild = Child#child{pid = NewPid},
-                    Children = lists:keyreplace(Pid, #child.pid, State#state.children, NewChild),
-                    {ok, State#state{children = Children}}
-            end;
+    case lists:keyfind(Pid, #child.pid, State#state.children) of
         false ->
-            Children = lists:keydelete(Pid, #child.pid, State#state.children),
-            {ok, State#state{children = Children}}
+            {ok, State};
+        #child{} = Child ->
+            case should_restart(Reason, Child#child.restart) of
+                true ->
+                    case try_start(Child) of
+                        {ok, NewPid, _Result} ->
+                            NewChild = Child#child{pid = NewPid},
+                            Children = lists:keyreplace(
+                                Pid, #child.pid, State#state.children, NewChild
+                            ),
+                            {ok, State#state{children = Children}}
+                    end;
+                false ->
+                    Children = lists:keydelete(Pid, #child.pid, State#state.children),
+                    {ok, State#state{children = Children}}
+            end
     end.
 
 should_restart(_Reason, permanent) ->
@@ -102,8 +179,23 @@ should_restart(Reason, transient) ->
         _any -> true
     end.
 
-handle_call(_Msg, _from, State) ->
-    {noreply, State}.
+handle_call({start_child, ChildSpec}, _From, #state{children = Children} = State) ->
+    Child = child_spec_to_record(ChildSpec),
+    #child{id = ID} = Child,
+    case lists:keyfind(ID, #child.id, State#state.children) of
+        #child{pid = undefined} ->
+            {reply, {error, already_present}, State};
+        #child{pid = Pid} ->
+            {reply, {error, {already_started, Pid}}, State};
+        false ->
+            case try_start(Child) of
+                {ok, Pid, Result} ->
+                    UpdatedChild = Child#child{pid = Pid},
+                    {reply, Result, State#state{children = [UpdatedChild | Children]}};
+                {error, _Reason} = ErrorT ->
+                    {reply, ErrorT, State}
+            end
+    end.
 
 handle_cast(_Msg, State) ->
     {noreply, State}.
@@ -118,3 +210,22 @@ handle_info({'EXIT', Pid, Reason}, State) ->
 handle_info(_Msg, State) ->
     %TODO: log unexpected message
     {noreply, State}.
+
+try_start(#child{start = {M, F, Args}} = Record) ->
+    try
+        case apply(M, F, Args) of
+            {ok, Pid} when is_pid(Pid) ->
+                {ok, Pid, {ok, Pid}};
+            {ok, Pid, Info} when is_pid(Pid) ->
+                {ok, Pid, {ok, Pid, Info}};
+            ignore ->
+                {ok, undefined, {ok, undefined}};
+            {error, Reason} ->
+                {error, {Reason, Record}};
+            Other ->
+                {error, {Other, Record}}
+        end
+    catch
+        error:Error ->
+            {error, {{'EXIT', Error}, Record}}
+    end.