fix(router): ask `mria:cluster_nodes/1` for current membership

Turns out `mria_membership` is not a good source of membership
information: it does not reflect membership changes resulted from
"force-leave" operations.

apps/emqx/src/emqx_router_helper.erl

@@ -192,7 +192,7 @@ init([]) ->
     ok = emqx_stats:update_interval(route_stats, fun ?MODULE:stats_fun/0),
     TRef = schedule_task(reconcile, ?RECONCILE_INTERVAL),
     State = #{
-        last_membership => mria_membership:nodelist(),
+        last_membership => mria:cluster_nodes(cores),
         tab_node_status => Tab,
         timer_reconcile => TRef
     },
@@ -289,19 +289,17 @@ handle_reconcile(State) ->
 reconcile(State = #{last_membership := MembersLast}) ->
     %% Find if there are discrepancies in membership.
     %% Missing core nodes must have been "force-left" from the cluster.
-    Members = mria_membership:nodelist(),
-    ok = lists:foreach(
-        fun(Node) ->
-            schedule_purge_left(Node),
-            record_node_left(Node)
-        end,
-        MembersLast -- Members
-    ),
+    Members = mria:cluster_nodes(cores),
+    ok = lists:foreach(fun(Node) -> record_node_left(Node) end, MembersLast -- Members),
     %% This is a fallback mechanism.
     %% Avoid purging live nodes, if missed lifecycle events for whatever reason.
-    ok = lists:foreach(fun record_node_alive/1, mria:running_nodes() ++ nodes()),
+    ok = lists:foreach(fun record_node_alive/1, mria:running_nodes()),
     State#{last_membership := Members}.
 
+select(Status) ->
+    MS = ets:fun2ms(fun(#ns{node = Node, status = S}) when S == Status -> Node end),
+    ets:select(?TAB_STATUS, MS).
+
 select_outdated(Status, Since0) ->
     MS = ets:fun2ms(
         fun(#ns{node = Node, status = S, since = Since}) when S == Status andalso Since < Since0 ->
@@ -325,6 +323,12 @@ schedule_purges(TS, State) ->
         fun schedule_purge/1,
         filter_replicants(select_outdated(down, TS - ?PURGE_DEAD_TIMEOUT))
     ),
+    %% Trigger purges for "force-left" nodes found during reconcile, if resposible.
+    ok = lists:foreach(
+        fun schedule_purge_left/1,
+        select(left)
+    ),
+    %% Otherwise, purge nodes marked left for a while.
     ok = lists:foreach(
         fun schedule_purge/1,
         select_outdated(left, TS - ?PURGE_LEFT_TIMEOUT)