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.

1 files changed, 12 insertions, 51 deletions

diff --git a/apps/rabbitmq_prelaunch/src/rabbit_prelaunch_conf.erl b/apps/rabbitmq_prelaunch/src/rabbit_prelaunch_conf.erl
index 9ff4cf09d0..ece600b68e 100644
--- a/apps/rabbitmq_prelaunch/src/rabbit_prelaunch_conf.erl
+++ b/apps/rabbitmq_prelaunch/src/rabbit_prelaunch_conf.erl
@@ -26,29 +26,13 @@ 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,
@@ -56,8 +40,7 @@ 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 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(),
@@ -186,26 +167,6 @@ 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) ->