Настройка репликации. Часть 1 #14

src/infra/infra_mnesia.erl

@@ -1,5 +1,5 @@
 %% ===================================================================
-%% EventHub – infra_mnesia (стабильная версия с автоочисткой при fresh старте)
+%% EventHub – infra_mnesia (финальная рабочая версия, задача #14)
 %% ===================================================================
 -module(infra_mnesia).
 -behaviour(gen_server).
@@ -20,6 +20,9 @@
   admin_audit, notification
 ]).
 
+%% Таблицы, которые должны иметь дисковые копии на каждом узле
+-define(DISC_TABLES, ?TABLES -- [session, admin_session]).
+
 -define(TABLE_WAIT_TIMEOUT, 5000).
 
 %% ===================================================================
@@ -43,8 +46,13 @@ init([]) ->
   {ok, #{}}.
 
 handle_call(init_tables, _From, State) ->
-  ok = maybe_recreate_schema(),
-  ok = ensure_cluster_join(),
+  ExtraNodes = application:get_env(eventhub, extra_db_nodes, []),
+  case ExtraNodes of
+    [] ->
+      ok = maybe_recreate_schema();
+    _ ->
+      ok = join_cluster(ExtraNodes)
+  end,
   lists:foreach(fun create_table/1, ?TABLES),
   ok = create_indices(),
   {reply, ok, State};
@@ -59,7 +67,7 @@ terminate(_Reason, _State) -> ok.
 code_change(_OldVsn, State, _Extra) -> {ok, State}.
 
 %% ===================================================================
-%% Проверка директории Mnesia и при необходимости пересоздание схемы
+%% Локальное создание схемы (только если нет extra_db_nodes)
 %% ===================================================================
 
 maybe_recreate_schema() ->
@@ -81,23 +89,61 @@ maybe_recreate_schema() ->
   end.
 
 %% ===================================================================
-%% Кластер
+%% Присоединение к кластеру – добавляет локальные дисковые копии таблиц
 %% ===================================================================
 
-ensure_cluster_join() ->
-  ExtraNodes = application:get_env(eventhub, extra_db_nodes, []),
-  case ExtraNodes of
-    [] -> ok;
-    Nodes ->
-      ok = mnesia:change_config(extra_db_nodes, Nodes),
-      case lists:member(node(), mnesia:table_info(schema, disc_copies)) of
-        false -> mnesia:add_table_copy(schema, node(), disc_copies);
-        true -> ok
-      end
+join_cluster(Nodes) ->
+  case mnesia:system_info(is_running) of
+    yes -> mnesia:stop();
+    no -> ok
+  end,
+  application:set_env(mnesia, extra_db_nodes, Nodes),
+  mnesia:start(),
+  ensure_schema_disc(),
+  % Дожидаемся появления всех таблиц в локальной схеме
+  wait_for_tables_available(),
+  lists:foreach(fun add_local_disc_copy/1, ?DISC_TABLES).
+
+wait_for_tables_available() ->
+  lists:foreach(fun(Tab) ->
+    wait_for_table(Tab)
+                end, ?DISC_TABLES).
+
+wait_for_table(Tab) ->
+  case lists:member(Tab, mnesia:system_info(tables)) of
+    true -> ok;
+    false ->
+      timer:sleep(100),
+      wait_for_table(Tab)
+  end.
+
+ensure_schema_disc() ->
+  case lists:member(node(), mnesia:table_info(schema, disc_copies)) of
+    false ->
+      io:format("Changing schema copy to disc...~n"),
+      case mnesia:change_table_copy_type(schema, node(), disc_copies) of
+        {atomic, ok} -> ok;
+        {aborted, {already_exists, _, _}} -> ok;
+        {aborted, Reason} -> error({failed_schema_disc, Reason})
+      end;
+    true -> ok
+  end.
+
+add_local_disc_copy(Tab) ->
+  case lists:member(node(), mnesia:table_info(Tab, disc_copies)) of
+    false ->
+      io:format("Adding local disc copy of table ~p...~n", [Tab]),
+      case mnesia:add_table_copy(Tab, node(), disc_copies) of
+        {atomic, ok} -> ok;
+        {aborted, {already_exists, _}} -> ok;
+        {aborted, Reason} ->
+          io:format("Could not add disc copy for ~p: ~p~n", [Tab, Reason])
+      end;
+    true -> ok
   end.
 
 %% ===================================================================
-%% Создание таблиц
+%% Создание / открытие таблиц
 %% ===================================================================
 
 create_table(Table) ->