rabbit_prelaunch_conf: Always handle config. files with Cuttlefish

This has several benefits:

1. It simplifies the code, all configuration being handled by the same
   code path (no more condition on Erlang-term-based vs. Cuttlefish).
   `rabbit_config` shrinks quite a lot in the process.

2. We can use additional configuration files AND an Erlang-term-based
   configuration file. In other words, it is possible to use the same
   existing Erlang-term-based file and introduce Cuttlefish files when
   needed.

   It allows a user to run RabbitMQ with:

   RABBITMQ_CONFIG_FILE=/path/to/rabbitmq.config \
   RABBITMQ_CONFIG_FILES=/path/to/conf.d/*.conf \
   ./sbin/rabbitmq-server

   A developer can do the same with `make run-broker`:

   make run-broker \
   RABBITMQ_CONFIG_FILES=/path/to/conf.d/*.conf

   In the example above, the main configuration file generated by
   rabbitmq-run.mk is an Erlang-term-based one.

This is implemented by calling Cuttlefish with a (possibly empty) list
of additional files and the Erlang-term-based file as the advanced
configuration file.

References #2180.

(cherry picked from commit 7edfe22)

Author: dumbbell

apps/rabbitmq_prelaunch/src/rabbit_prelaunch_conf.erl

@@ -26,38 +26,21 @@ setup(Context) ->
     AdvancedConfigFile = find_actual_advanced_config_file(Context),
     State = case find_actual_main_config_file(Context) of
                 {MainConfigFile, erlang} ->
-                    case AdditionalConfigFiles of
-                        [] ->
-                            ok;
-                        _ ->
-                            rabbit_log_prelaunch:notice(
-                              "The following additional configuration "
-                              "files are not loaded when the main "
-                              "configuration file uses the Erlang terms "
-                              "based format"),
-                            lists:foreach(
-                              fun(File) ->
-                                      rabbit_log_prelaunch:notice(
-                                        "  - ~ts", [File])
-                              end,
-                              AdditionalConfigFiles)
-                    end,
-                    Config = load_erlang_term_based_config_file(
-                               MainConfigFile),
+                    Config = load_cuttlefish_config_file(Context,
+                                                         AdditionalConfigFiles,
+                                                         MainConfigFile),
                     Apps = [App || {App, _} <- Config],
                     decrypt_config(Apps),
-                    #{config_type => erlang,
-                      config_files => [MainConfigFile],
-                      config_advanced_file => undefined};
+                    #{config_files => AdditionalConfigFiles,
+                      config_advanced_file => MainConfigFile};
                 {MainConfigFile, cuttlefish} ->
                     ConfigFiles = [MainConfigFile | AdditionalConfigFiles],
                     Config = load_cuttlefish_config_file(Context,
                                                          ConfigFiles,
                                                          AdvancedConfigFile),
                     Apps = [App || {App, _} <- Config],
                     decrypt_config(Apps),
-                    #{config_type => cuttlefish,
-                      config_files => ConfigFiles,
+                    #{config_files => ConfigFiles,
                       config_advanced_file => AdvancedConfigFile};
                 undefined when AdditionalConfigFiles =/= [] ->
                     ConfigFiles = AdditionalConfigFiles,
@@ -66,23 +49,21 @@ setup(Context) ->
                                                          AdvancedConfigFile),
                     Apps = [App || {App, _} <- Config],
                     decrypt_config(Apps),
-                    #{config_type => cuttlefish,
-                      config_files => ConfigFiles,
+                    #{config_files => ConfigFiles,
                       config_advanced_file => AdvancedConfigFile};
                 undefined when AdvancedConfigFile =/= undefined ->
                     rabbit_log_prelaunch:warning(
                       "Using RABBITMQ_ADVANCED_CONFIG_FILE: ~s",
                       [AdvancedConfigFile]),
-                    Config = load_erlang_term_based_config_file(
-                               AdvancedConfigFile),
+                    Config = load_cuttlefish_config_file(Context,
+                                                         AdditionalConfigFiles,
+                                                         AdvancedConfigFile),
                     Apps = [App || {App, _} <- Config],
                     decrypt_config(Apps),
-                    #{config_type => erlang,
-                      config_files => [AdvancedConfigFile],
+                    #{config_files => AdditionalConfigFiles,
                       config_advanced_file => AdvancedConfigFile};
                 undefined ->
-                    #{config_type => undefined,
-                      config_files => [],
+                    #{config_files => [],
                       config_advanced_file => undefined}
             end,
     ok = override_with_hard_coded_critical_config(),
@@ -187,26 +168,6 @@ determine_config_format(File) ->
             end
     end.
 
-load_erlang_term_based_config_file(ConfigFile) ->
-    rabbit_log_prelaunch:debug(
-      "Loading configuration file \"~ts\" (Erlang terms based)", [ConfigFile]),
-    case file:consult(ConfigFile) of
-        {ok, [Config]} when is_list(Config) ->
-            apply_erlang_term_based_config(Config),
-            Config;
-        {ok, OtherTerms} ->
-            rabbit_log_prelaunch:error(
-              "Failed to load configuration file \"~ts\", "
-              "incorrect format: ~p",
-              [ConfigFile, OtherTerms]),
-            throw({error, failed_to_parse_configuration_file});
-        {error, Reason} ->
-            rabbit_log_prelaunch:error(
-              "Failed to load configuration file \"~ts\": ~ts",
-              [ConfigFile, file:format_error(Reason)]),
-            throw({error, failed_to_read_configuration_file})
-    end.
-
 load_cuttlefish_config_file(Context,
                             ConfigFiles,
                             AdvancedConfigFile) ->

src/rabbit_config.erl

@@ -10,24 +10,10 @@
 
 -type config_location() :: string().
 
-%% we support both the classic Erlang term
-%% config file (rabbitmq.config) as well as rabbitmq.conf
-legacy_erlang_term_config_used() ->
-    case get_prelaunch_config_state() of
-        #{config_type := erlang,
-          config_advanced_file := undefined} ->
-            true;
-        _ ->
-            false
-    end.
-
 get_confs() ->
     case get_prelaunch_config_state() of
-        #{config_files := Confs} ->
-            [ filename:rootname(Conf, ".conf") ++ ".conf"
-              || Conf <- Confs ];
-        _ ->
-            []
+        #{config_files := Confs} -> Confs;
+        _                        -> []
     end.
 
 schema_dir() ->
@@ -43,7 +29,7 @@ schema_dir() ->
 get_advanced_config() ->
     case get_prelaunch_config_state() of
         %% There can be only one advanced.config
-        #{config_advanced_file := FileName} ->
+        #{config_advanced_file := FileName} when FileName =/= undefined ->
             case rabbit_file:is_file(FileName) of
                 true  -> FileName;
                 false -> none
@@ -53,47 +39,13 @@ get_advanced_config() ->
 
 -spec config_files() -> [config_location()].
 config_files() ->
-    case legacy_erlang_term_config_used() of
-        true ->
-            case get_prelaunch_config_state() of
-                #{config_files := Files} ->
-                    [ filename:absname(filename:rootname(File) ++ ".config")
-                      || File <- Files];
-                _ ->
-                    case config_setting() of
+    ConfFiles = [filename:absname(File) || File <- get_confs(),
+                                           filelib:is_regular(File)],
+    AdvancedFiles = case get_advanced_config() of
                         none -> [];
-                        File -> [filename:absname(filename:rootname(File, ".config") ++ ".config")
-                                 ++
-                                 " (not found)"]
-                    end
-            end;
-        false ->
-            ConfFiles = [filename:absname(File) || File <- get_confs(),
-                                                   filelib:is_regular(File)],
-            AdvancedFiles = case get_advanced_config() of
-                none -> [];
-                FileName -> [filename:absname(FileName)]
-            end,
-            AdvancedFiles ++ ConfFiles
-
-    end.
+                        FileName -> [filename:absname(FileName)]
+                    end,
+    AdvancedFiles ++ ConfFiles.
 
 get_prelaunch_config_state() ->
     rabbit_prelaunch_conf:get_config_state().
-
-%% This is a pain. We want to know where the config file is. But we
-%% can't specify it on the command line if it is missing or the VM
-%% will fail to start, so we need to find it by some mechanism other
-%% than init:get_arguments/0. We can look at the environment variable
-%% which is responsible for setting it... but that doesn't work for a
-%% Windows service since the variable can change and the service not
-%% be reinstalled, so in that case we add a magic application env.
-config_setting() ->
-    case application:get_env(rabbit, windows_service_config) of
-        {ok, File1} -> File1;
-        undefined   ->
-            case application:get_env(rabbitmq_prelaunch, context) of
-                #{main_config_file := File2} -> File2;
-                _                            -> none
-            end
-    end.