revert: #263 and #264

We don't need to check where was the table loaded from, since we have
fixed the problem in OTP-24.3.4.17-1

Author: terry-xiaoyu

src/ekka.appup.src

@@ -3,6 +3,7 @@
 {VSN,
   [{"0.8.1.17",
     [{load_module,ekka_cluster,brutal_purge,soft_purge,[]},
+     {load_module,ekka_mnesia,brutal_purge,soft_purge,[]},
      {load_module,ekka_autoheal,brutal_purge,soft_purge,[]}]},
    {"0.8.1.16",
     [{load_module,ekka_cluster,brutal_purge,soft_purge,[]},
@@ -142,6 +143,7 @@
      {load_module,ekka_dist,brutal_purge,soft_purge,[]}]}],
   [{"0.8.1.17",
     [{load_module,ekka_cluster,brutal_purge,soft_purge,[]},
+     {load_module,ekka_mnesia,brutal_purge,soft_purge,[]},
      {load_module,ekka_autoheal,brutal_purge,soft_purge,[]}]},
    {"0.8.1.16",
     [{load_module,ekka_cluster,brutal_purge,soft_purge,[]},

src/ekka_mnesia.erl

@@ -310,119 +310,7 @@ wait_for(stop) ->
 
 wait_for(tables) ->
     Tables = mnesia:system_info(local_tables),
-    case do_wait_for_tables(Tables) of
-        {error, _} = Error ->
-            Error;
-        ok ->
-            case mnesia:system_info(db_nodes) -- [node()] of
-                [] -> ok;
-                _OtherDBNodes ->
-                    case ekka:env(skip_table_load_check, false) of
-                        true ->
-                            logger:warning("Skipping table load origin check because "
-                                           "'skip_table_load_check' is set to true. "
-                                           "This may hide data inconsistency issues, "
-                                           "please unset this option after the node is up."),
-                            ok;
-                        false ->
-                            %% Make sure we have loaded tables from a remote node,
-                            %% or force-loaded from local copies by the user.
-                            RemoteActiveReplicas = get_remote_active_replicas(),
-                            case check_tables_load_from(Tables, RemoteActiveReplicas) of
-                                ok -> ok;
-                                {error, _} = Error -> Error
-                            end
-                    end
-            end
-    end.
-
-check_tables_load_from([], _) ->
-    ok;
-check_tables_load_from([schema | Rest], RemoteActiveReplicas) ->
-    check_tables_load_from(Rest, RemoteActiveReplicas);
-check_tables_load_from([Tab | Rest], RemoteActiveReplicas) ->
-    LoadFrom = mnesia_lib:val({Tab, load_node}),
-    LoadReason = mnesia_lib:val({Tab, load_reason}),
-    case mnesia:table_info(Tab, local_content) of
-        true ->
-            check_tables_load_from(Rest, RemoteActiveReplicas);
-        false ->
-            Self = node(),
-            RemoteReplicas = get_remote_replicas(Tab),
-            case {LoadFrom, RemoteReplicas, RemoteActiveReplicas} of
-                {Self, [], _} ->
-                    %% we have no remote replica
-                    check_tables_load_from(Rest, RemoteActiveReplicas);
-                {Self, [_ | _], []} ->
-                    %% we have one or more remote replicas but we are loaded from local,
-                    %% maybe force loaded by the user, as we have no active replicas other than current node.
-                    logger:warning(
-                        "Mnesia loaded table ~p from local copy while remote replicas ~p "
-                        "exist but none are active (load_reason=~p). "
-                        "If you have intentionally force-loaded this table (e.g. after removing "
-                        "remote nodes from the cluster), this warning can be safely ignored. "
-                        "Otherwise, please check the network connectivity between cluster nodes, "
-                        "ensure remote nodes are reachable, and restart EMQX.",
-                        [Tab, RemoteReplicas, LoadReason]),
-                    check_tables_load_from(Rest, RemoteActiveReplicas);
-                {Self, [_ | _], [_ | _]} ->
-                    %% prevent the current node from starting as the table is loaded from local and there
-                    %% are other active replicas in the cluster
-                    logger:error(
-                        "Mnesia loaded table ~p from local copy while remote active replicas ~p "
-                        "are available (load_reason=~p). "
-                        "This is likely caused by a network partition or misconfiguration. "
-                        "The node refuses to start to prevent data inconsistency. "
-                        "Please fix the network connectivity between cluster nodes and restart EMQX.",
-                        [Tab, RemoteActiveReplicas, LoadReason]),
-                    {error, {tab_loaded_from_local_copy, Tab, LoadReason}};
-                {Self, unknown, _} ->
-                    logger:error(
-                        "Mnesia loaded table ~p from local copy but this table only resides "
-                        "on remote nodes (load_reason=~p). "
-                        "This is likely caused by a network partition during startup. "
-                        "Please fix the network connectivity between cluster nodes and restart EMQX.",
-                        [Tab, LoadReason]),
-                    {error, {tab_loaded_from_local_copy, Tab, LoadReason}};
-                {_, _, _} ->
-                    check_tables_load_from(Rest, RemoteActiveReplicas)
-            end
-    end.
-
-%% @doc Get the remote nodes that are running emqx.
-%%
-%% Q: Why not use mnesia:table_info(Tab, active_replicas) -- [Self]?
-%% A: Because it will cause a deadlock when all other nodes are restarting and waiting for
-%% this node to start.
-get_remote_active_replicas() ->
-    RunningNodes = ekka_mnesia:running_nodes() -- [node()],
-    Result = erpc:multicall(RunningNodes, application, which_applications, [], 5000),
-    Zip = lists:zip(RunningNodes, Result),
-    lists:filtermap(
-        fun
-            ({Node, {ok, Applications}}) ->
-                case lists:keymember(emqx, 1, Applications) of
-                    true ->
-                        {true, Node};
-                    false ->
-                        false
-                end;
-            ({_, {error, _}}) ->
-                false
-        end,
-        Zip
-    ).
-
-get_remote_replicas(Tab) ->
-    case mnesia:table_info(Tab, storage_type) of
-        unknown ->
-            unknown;
-        _ ->
-            RamCopies = mnesia:table_info(Tab, ram_copies),
-            DiscCopies = mnesia:table_info(Tab, disc_copies),
-            DiscOnlyCopies = mnesia:table_info(Tab, disc_only_copies),
-            lists:usort((RamCopies ++ DiscCopies ++ DiscOnlyCopies) -- [node()])
-    end.
+    do_wait_for_tables(Tables).
 
 do_wait_for_tables(Tables) ->
     case mnesia:wait_for_tables(Tables, 30000) of

test/ekka_mnesia_SUITE.erl

@@ -141,11 +141,7 @@ t_diagnosis_tab(_)->
         %% Start mnesia on N2.
         ok = rpc:call(N2, ekka_mnesia, start, []),
 
-        %% Restart mnesia on N1 so it loads the table from N2
-        %% instead of keeping the stale local copy.
-        %% (check_tables_load_from rejects locally-loaded tables
-        %% when remote active replicas exist.)
-        stopped = rpc:call(N1, mnesia, stop, []),
+        %% Start ekka_mnesia on N1, no blocking
         ok = rpc:call(N1, ekka_mnesia, start, []),
 
         %% Check tables are loaded on two