File 7861-Improve-supervisor-restart-calculation.patch of Package erlang
From 6b318376a34a0cc488c37864443ae53f38c75b7f Mon Sep 17 00:00:00 2001
From: Maria Scott <maria-12648430@hnc-agency.org>
Date: Wed, 13 Mar 2024 16:12:45 +0100
Subject: [PATCH] Improve supervisor restart calculation
---
lib/stdlib/src/supervisor.erl | 53 ++++++++++++++++++++++-------------
1 file changed, 34 insertions(+), 19 deletions(-)
diff --git a/lib/stdlib/src/supervisor.erl b/lib/stdlib/src/supervisor.erl
index 3c1917db27..125c0fafc0 100644
--- a/lib/stdlib/src/supervisor.erl
+++ b/lib/stdlib/src/supervisor.erl
@@ -456,12 +456,15 @@ see more details [above](`m:supervisor#sup_flags`).
intensity = 1 :: non_neg_integer(),
period = 5 :: pos_integer(),
restarts = [],
+ nrestarts = 0,
dynamic_restarts = 0 :: non_neg_integer(),
auto_shutdown = never :: auto_shutdown(),
module,
args}).
-type state() :: #state{}.
+-define(DIRTY_RESTART_LIMIT, 1000).
+
-define(is_simple(State), State#state.strategy =:= simple_one_for_one).
-define(is_temporary(_Child_), _Child_#child.restart_type=:=temporary).
-define(is_transient(_Child_), _Child_#child.restart_type=:=transient).
@@ -2064,27 +2067,39 @@ child_to_spec(#child{id = Id,
%%% Returns: {ok, State'} | {terminate, State'}
%%% ------------------------------------------------------
-add_restart(State) ->
- I = State#state.intensity,
- P = State#state.period,
- R = State#state.restarts,
- Now = erlang:monotonic_time(1),
- R1 = add_restart(R, Now, P),
- State1 = State#state{restarts = R1},
- case length(R1) of
- CurI when CurI =< I ->
- {ok, State1};
- _ ->
- {terminate, State1}
+%% shortcut: if the intensity limit is 0, no restarts are allowed;
+%% it is safe to disallow the restart flat out
+add_restart(State=#state{intensity=0}) ->
+ {terminate, State};
+%% shortcut: if the number of restarts is below the intensity
+%% limit, it is safe to allow the restart, add the restart to
+%% the list and not care about expired restarts; to prevent
+%% accumulating a large list of expired restarts over time,
+%% this shortcut is limited to ?DIRTY_RESTART_LIMIT restarts
+add_restart(State=#state{intensity=I, restarts=R, nrestarts=NR})
+ when NR < ?DIRTY_RESTART_LIMIT, NR < I ->
+ {ok, State#state{restarts=[erlang:monotonic_time(second)|R], nrestarts=NR + 1}};
+%% calculate the real number of restarts within the period
+%% and remove expired restarts; based on the calculated number
+%% of restarts, allow or disallow the restart
+add_restart(State=#state{intensity=I, period=P, restarts=R}) ->
+ Now = erlang:monotonic_time(second),
+ Treshold = Now - P,
+ case can_restart(I - 1, Treshold, R, [], 0) of
+ {true, NR1, R1} ->
+ {ok, State#state{restarts = [Now|R1], nrestarts = NR1 + 1}};
+ {false, NR1, R1} ->
+ {terminate, State#state{restarts = R1, nrestarts = NR1}}
end.
-add_restart(Restarts0, Now, Period) ->
- Threshold = Now - Period,
- Restarts1 = lists:takewhile(
- fun (R) -> R >= Threshold end,
- Restarts0
- ),
- [Now | Restarts1].
+can_restart(_, _, [], Acc, NR) ->
+ {true, NR, lists:reverse(Acc)};
+can_restart(_, Treshold, [Restart|_], Acc, NR) when Restart < Treshold ->
+ {true, NR, lists:reverse(Acc)};
+can_restart(0, _, [_|_], Acc, NR) ->
+ {false, NR, lists:reverse(Acc)};
+can_restart(N, Treshold, [Restart|Restarts], Acc, NR) ->
+ can_restart(N - 1, Treshold, Restarts, [Restart|Acc], NR + 1).
%%% ------------------------------------------------------
%%% Error and progress reporting.
--
2.43.0
