File 0740-logger-Make-logger_proxy-more-robust-at-startup.patch of Package erlang

From aa4457514d1fdcfb543ada9c502bd11f9ad58c9f Mon Sep 17 00:00:00 2001
From: Lukas Larsson <lukas@erlang.org>
Date: Tue, 21 Jan 2020 17:20:10 +0100
Subject: [PATCH 4/4] logger: Make logger_proxy more robust at startup

If a remote log event happens before the logger_proxy
is started the logger_server would crash which would pull
down the entire node. Now we instead try to do the logging
in the calling processes.
---
 lib/kernel/src/logger_proxy.erl        | 18 +++++++++++++-----
 lib/kernel/test/logger_proxy_SUITE.erl | 14 ++++++++++++++
 2 files changed, 27 insertions(+), 5 deletions(-)

diff --git a/lib/kernel/src/logger_proxy.erl b/lib/kernel/src/logger_proxy.erl
index 24b293805c..6ab8e3e4c5 100644
--- a/lib/kernel/src/logger_proxy.erl
+++ b/lib/kernel/src/logger_proxy.erl
@@ -42,11 +42,16 @@
       StringOrReport :: unicode:chardata() | logger:report(),
       Meta :: logger:metadata().
 log(RemoteLog) ->
-    Olp = persistent_term:get(?MODULE),
-    case logger_olp:get_pid(Olp) =:= self() of
+    Olp = persistent_term:get(?MODULE, undefined),
+    case (Olp =:= undefined) orelse (logger_olp:get_pid(Olp) =:= self()) of
         true ->
             %% This happens when the log event comes from the
             %% emulator, and the group leader is on a remote node.
+            %%
+            %% OR
+            %%
+            %% when we are to log a remote message before the logger_proxy
+            %% has started
             _ = handle_load(RemoteLog, no_state),
             ok;
         false ->
@@ -112,9 +117,12 @@ init([]) ->
 
 %% Log event to send to the node where the group leader of it's client resides
 handle_load({remote,Node,Log},State) ->
-    %% If the connection is overloaded (send_nosuspend returns false),
-    %% we drop the message.
-    _ = erlang:send_nosuspend({?SERVER,Node},Log),
+    case erlang:send({?SERVER,Node},Log,[nosuspend]) of
+        _ok_or_nosuspend ->
+            %% If the connection is overloaded (send returns nosuspend),
+            %% we drop the message.
+            ok
+    end,
     State;
 %% Log event to log on this node
 handle_load({log,Level,Format,Args,Meta},State) ->
diff --git a/lib/kernel/test/logger_proxy_SUITE.erl b/lib/kernel/test/logger_proxy_SUITE.erl
index 777531e4ed..bae2bd8d17 100644
--- a/lib/kernel/test/logger_proxy_SUITE.erl
+++ b/lib/kernel/test/logger_proxy_SUITE.erl
@@ -72,6 +72,7 @@ all() ->
     [basic,
      emulator,
      remote,
+     remote_disconnect,
      remote_emulator,
      config,
      restart_after,
@@ -118,6 +119,19 @@ remote(Config) ->
 remote(cleanup,_Config) ->
     ok = logger:remove_handler(?HNAME).
 
+remote_disconnect(Config) ->
+    {ok,_,Node} = logger_test_lib:setup(Config,[{logger,[{proxy,#{}}]}]),
+    ok = logger:add_handler(?HNAME,?MODULE,#{config=>self()}),
+    RemoteGL = rpc:call(Node, erlang, whereis, [user]),
+    net_kernel:disconnect(Node),
+    L1 = ?LOC#{ gl => RemoteGL }, logger:notice("Log from ~p; ~p",[?FUNCTION_NAME,?LINE],L1),
+    ok = ensure(L1),
+    L2 = ?LOC#{ gl => RemoteGL }, logger:notice([{test_case,?FUNCTION_NAME},{line,?LINE}],L2),
+    ok = ensure(L2),
+    ok.
+remote_disconnect(cleanup,_Config) ->
+    ok = logger:remove_handler(?HNAME).
+
 remote_emulator(Config) ->
     {ok,_,Node} = logger_test_lib:setup(Config,[{logger,[{proxy,#{}}]}]),
     ok = logger:add_handler(?HNAME,?MODULE,#{config=>self()}),
-- 
2.16.4