Rework logger configuration and add logger config generator

README.md

@@ -1179,8 +1179,6 @@ support these options. A toplevel dependency will override any lager
 dependencies in any of your application's dependencies and thus ensure the parse
 transform is the right version.
 
-XXX the following is not yet implemented:
-
 To generate a logger configuration from your lager configuration you can do:
 
 ```
@@ -1197,6 +1195,12 @@ lager configure logger you can, in your sys.config in the lager stanza:
 ]}
 ```
 
+Alternatively you can use:
+
+```
+lager:configure_logger()
+```
+
 3.x Changelog
 -------------
 3.6.8 - 21 December 2018

src/lager.erl

@@ -37,7 +37,7 @@
         update_loglevel_config/1, posix_error/1, set_loghwm/2, set_loghwm/3, set_loghwm/4,
         safe_format/3, safe_format_chop/3, unsafe_format/2, dispatch_log/5, dispatch_log/7, dispatch_log/9,
         do_log/9, do_log/10, do_log_unsafe/10, pr/2, pr/3, pr_stacktrace/1, pr_stacktrace/2,
-        configure_logger/0]).
+        generate_logger_config/0, configure_logger/0]).
 
 -type log_level() :: none | debug | info | notice | warning | error | critical | alert | emergency.
 -type log_level_number() :: 0..7.
@@ -690,54 +690,62 @@ rotate_handler(Handler) ->
 rotate_handler(Handler, Sink) ->
     gen_event:call(Sink, Handler, rotate, ?ROTATE_TIMEOUT).
 
+generate_logger_config() ->
+    Handlers = application:get_env(lager, handlers, lager_app:default_handlers()),
+    {Level, NewHandlers} = generate_logger_handlers(Handlers, {notice, []}),
+    {kernel, [{logger_level, Level}, {logger, NewHandlers}]}.
 
 configure_logger() ->
     Handlers = application:get_env(lager, handlers, lager_app:default_handlers()),
     WhitelistedLoggerHandlers = application:get_env(lager, whitelisted_logger_handlers, []),
     [ ok = logger:remove_handler(Id) || #{id := Id} <- logger:get_handler_config(), not lists:member(Id, WhitelistedLoggerHandlers) ],
-    add_logger_handlers(Handlers).
+    {Level, NewHandlers} = generate_logger_handlers(Handlers, {notice, []}),
+    logger:set_primary_config(maps:merge(logger:get_primary_config(), #{level => Level})),
+    [ ok = logger:add_handler(HandlerId, HandlerModule, HandlerConfig) || {handler, HandlerId, HandlerModule, HandlerConfig} <- NewHandlers ],
+    ok.
 
-add_logger_handlers([]) ->
-    ok;
-add_logger_handlers([{lager_console_backend, Config}|Tail]) ->
+generate_logger_handlers([], Acc) ->
+    Acc;
+generate_logger_handlers([{lager_console_backend, Config}|Tail], {CurrentLevel, Acc}) ->
     Level = proplists:get_value(level, Config, info),
     Formatter = proplists:get_value(formatter, Config, lager_default_formatter),
     FormatterConfig = proplists:get_value(formatter_config, Config, []),
-    logger:add_handler(console, logger_std_h, #{level => Level, formatter =>
-                                                {lager_logger_formatter, #{report_cb => fun lager_logger_formatter:report_cb/1,
-                                                                           formatter => Formatter,
-                                                                           formatter_config => FormatterConfig}}}),
-    PriConfig = #{level := CurrentLevel} = logger:get_primary_config(),
-    case lager_util:level_to_num(Level) > lager_util:level_to_num(CurrentLevel) of
-        true ->
-            logger:set_primary_config(maps:merge(PriConfig, #{level => Level}));
-        false ->
-            ok
-    end,
-    add_logger_handlers(Tail);
-add_logger_handlers([{lager_file_backend, Config}|Tail]) ->
+    Handler = {handler, console, logger_std_h, #{level => Level, formatter =>
+                                                 {lager_logger_formatter, #{report_cb => fun lager_logger_formatter:report_cb/1,
+                                                                            formatter => Formatter,
+                                                                            formatter_config => FormatterConfig}}}},
+    NewLevel = case lager_util:level_to_num(Level) > lager_util:level_to_num(CurrentLevel) of
+                   true ->
+                       Level;
+                   false ->
+                       CurrentLevel
+               end,
+    generate_logger_handlers(Tail, {NewLevel, [Handler|Acc]});
+generate_logger_handlers([{lager_file_backend, Config}|Tail], {CurrentLevel, Acc}) ->
     Level = proplists:get_value(level, Config, info),
     File = proplists:get_value(file, Config),
+    LogRoot = application:get_env(lager, log_root, ""),
     Size = proplists:get_value(size, Config),
     Count = proplists:get_value(count, Config),
     Formatter = proplists:get_value(formatter, Config, lager_default_formatter),
     FormatterConfig = proplists:get_value(formatter_config, Config, []),
-    logger:add_handler(list_to_atom(File), logger_disk_log_h, #{level => Level,
-                                                     file => File,
-                                                     max_no_files => Count,
-                                                     max_no_bytes => Size,
-                                                     formatter =>
-                                                     {lager_logger_formatter, #{report_cb => fun lager_logger_formatter:report_cb/1,
-                                                                                formatter => Formatter,
-                                                                                formatter_config => FormatterConfig}}}),
-    PriConfig = #{level := CurrentLevel} = logger:get_primary_config(),
-    case lager_util:level_to_num(Level) > lager_util:level_to_num(CurrentLevel) of
-        true ->
-            logger:set_primary_config(maps:merge(PriConfig, #{level => Level}));
-        false ->
-            ok
-    end,
-    add_logger_handlers(Tail).
+    %% XXX I don't think disk_log is suitable as it is, we should provide a logger compatible version of
+    %% lager's file_backend and try to patch disk_log upstream
+    Handler = {handler, list_to_atom(File), logger_disk_log_h, #{level => Level,
+                                                                 file => filename:join(LogRoot, File),
+                                                                 max_no_files => Count,
+                                                                 max_no_bytes => Size,
+                                                                 formatter =>
+                                                                 {lager_logger_formatter, #{report_cb => fun lager_logger_formatter:report_cb/1,
+                                                                                            formatter => Formatter,
+                                                                                            formatter_config => FormatterConfig}}}},
+    NewLevel = case lager_util:level_to_num(Level) > lager_util:level_to_num(CurrentLevel) of
+                   true ->
+                       Level;
+                   false ->
+                       CurrentLevel
+               end,
+    generate_logger_handlers(Tail, {NewLevel, [Handler|Acc]}).
 
 
 %% @private

src/lager_app.erl

@@ -235,6 +235,12 @@ start(_StartType, _StartArgs) ->
             clean_up_config_checks(),
             {ok, Pid, SavedHandlers};
         true ->
+            case application:get_env(lager, configure_logger, false) of
+                true ->
+                    ok = lager:configure_logger();
+                false ->
+                    ok
+            end,
             {ok, Pid}
     end.