chore: exit with non-zero status if config initialization failed

apps/emqx/src/emqx_app.erl

@@ -72,9 +72,13 @@ set_init_config_load_done() ->
 get_init_config_load_done() ->
     application:get_env(emqx, init_config_load_done, false).
 
+%% @doc Set the transaction id from which this node should start applying after boot.
+%% The transaction ID is received from the core node which we just copied the latest
+%% config from.
 set_init_tnx_id(TnxId) ->
     application:set_env(emqx, cluster_rpc_init_tnx_id, TnxId).
 
+%% @doc Get the transaction id from which this node should start applying after boot.
 get_init_tnx_id() ->
     application:get_env(emqx, cluster_rpc_init_tnx_id, -1).
 

apps/emqx_conf/src/emqx_cluster_rpc.erl

@@ -275,8 +275,13 @@ init([Node, RetryMs]) ->
     _ = mria:wait_for_tables([?CLUSTER_MFA, ?CLUSTER_COMMIT]),
     {ok, _} = mnesia:subscribe({table, ?CLUSTER_MFA, simple}),
     State = #{node => Node, retry_interval => RetryMs},
+    %% The init transaction ID is set in emqx_conf_app after
+    %% it has fetched the latest config from one of the core nodes
     TnxId = emqx_app:get_init_tnx_id(),
     ok = maybe_init_tnx_id(Node, TnxId),
+    %% Now continue with the normal catch-up process
+    %% That is: apply the missing transactions after the config
+    %% was copied until now.
     {ok, State, {continue, ?CATCH_UP}}.
 
 %% @private
@@ -396,6 +401,7 @@ get_cluster_tnx_id() ->
         Id -> Id
     end.
 
+%% The entry point of a config change transaction.
 init_mfa(Node, MFA) ->
     mnesia:write_lock_table(?CLUSTER_MFA),
     LatestId = get_cluster_tnx_id(),

apps/emqx_conf/src/emqx_conf_app.erl

@@ -38,7 +38,7 @@ start(_StartType, _StartArgs) ->
                 reason => E,
                 stacktrace => St
             }),
-            init:stop()
+            init:stop(1)
     end,
     ok = emqx_config_logger:refresh_config(),
     emqx_conf_sup:start_link().