From 395dbad6bcc38c3384840674f40657273b05b14a Mon Sep 17 00:00:00 2001
From: Lukas Larsson <lukas@erlang.org>
Date: Tue, 8 May 2018 16:13:50 +0200
Subject: logger: Rework configuration of logger

Most logger configuration that was possible through
kernel application variables have been moved into a
common 'logger' application environment in kernel.

Now all the configuration possible through the logger
API can be done as sys config.

The handler started by kernel has been renamed to 'default'
instead of logger_std_h.

There is a new logger:setup_handlers/1 function that given an
application name can be used to setup handlers in other applications.
---
 lib/kernel/src/logger_simple.erl | 69 ++++++++++++++--------------------------
 1 file changed, 23 insertions(+), 46 deletions(-)

(limited to 'lib/kernel/src/logger_simple.erl')

diff --git a/lib/kernel/src/logger_simple.erl b/lib/kernel/src/logger_simple.erl
index a1b427b96c..5272455a2d 100644
--- a/lib/kernel/src/logger_simple.erl
+++ b/lib/kernel/src/logger_simple.erl
@@ -20,29 +20,10 @@
 -module(logger_simple).
 
 -export([adding_handler/2, removing_handler/2, log/2]).
--export([get_buffer/0]).
 
 %% This module implements a simple handler for logger. It is the
 %% default used during system start.
 
-%%%-----------------------------------------------------------------
-%%% API
-get_buffer() ->
-    case whereis(?MODULE) of
-        undefined ->
-            {error,noproc};
-        Pid ->
-            Ref = erlang:monitor(process,Pid),
-            Pid ! {get_buffer,self()},
-            receive
-                {buffer,Buffer} ->
-                    erlang:demonitor(Ref,[flush]),
-                    {ok,Buffer};
-                {'DOWN',Ref,process,Pid,Reason} ->
-                    {error,Reason}
-            end
-    end.
-
 %%%-----------------------------------------------------------------
 %%% Logger callback
 
@@ -50,7 +31,7 @@ adding_handler(?MODULE,Config) ->
     Me = self(),
     case whereis(?MODULE) of
         undefined ->
-            {Pid,Ref} = spawn_opt(fun() -> init(Me,Config) end,
+            {Pid,Ref} = spawn_opt(fun() -> init(Me) end,
                                   [link,monitor,{message_queue_data,off_heap}]),
             receive
                 {'DOWN',Ref,process,Pid,Reason} ->
@@ -102,48 +83,44 @@ log(_,_) ->
 
 %%%-----------------------------------------------------------------
 %%% Process
-init(Starter,Config) ->
+init(Starter) ->
     register(?MODULE,self()),
     Starter ! {self(),started},
-    BufferSize =
-        case Config of
-            #{?MODULE:=#{buffer:=true}} ->
-                10;
-            _ ->
-                infinity
-        end,
-    loop(#{buffer_size=>BufferSize,dropped=>0,buffer=>[]},infinity).
+    loop(#{buffer_size=>10,dropped=>0,buffer=>[]}).
 
-loop(Buffer,Timeout) ->
+loop(Buffer) ->
     receive
         stop ->
-            ok;
-        {get_buffer,From} ->
-            loop(Buffer#{send_to=>From},0);
+            %% We replay the logger messages of there is
+            %% a default handler when the simple handler
+            %% is removed.
+            case logger:get_handler_config(default) of
+                {ok, _} ->
+                    replay_buffer(Buffer);
+                _ ->
+                    ok
+            end;
         {log,#{msg:=_,meta:=#{time:=_}}=Log} ->
             do_log(Log),
-            loop(update_buffer(Buffer,Log),Timeout);
+            loop(update_buffer(Buffer,Log));
         _ ->
             %% Unexpected message - flush it!
-            loop(Buffer,Timeout)
-    after Timeout ->
-            #{dropped:=D,buffer:=B,send_to:=Pid} = Buffer,
-            LogList = lists:reverse(B) ++ drop_msg(D),
-            Pid ! {buffer,LogList},
-            loop(Buffer#{buffer_size=>infinity,
-                         dropped=>0,
-                         buffer=>[],
-                         send_to=>false},
-                 infinity)
+            loop(Buffer)
     end.
 
-update_buffer(#{buffer_size:=infinity}=Buffer,_Log) ->
-    Buffer;
 update_buffer(#{buffer_size:=0,dropped:=D}=Buffer,_Log) ->
     Buffer#{dropped=>D+1};
 update_buffer(#{buffer_size:=S,buffer:=B}=Buffer,Log) ->
     Buffer#{buffer_size=>S-1,buffer=>[Log|B]}.
 
+replay_buffer(#{ dropped := D, buffer := Buffer }) ->
+    lists:foreach(
+      fun F(#{msg := {Tag, Msg}} = L) when Tag =:= string; Tag =:= report ->
+              F(L#{ msg := Msg });
+          F(#{ level := Level, msg := Msg, meta := MD}) ->
+              logger:log(Level, Msg, MD)
+      end, lists:reverse(Buffer, drop_msg(D))).
+
 drop_msg(0) ->
     [];
 drop_msg(N) ->
-- 
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