Mnesia: Ask to leave a cluster and retry to join if cluster already consider node a member.

Khepri: no-op. Khepri is less strict already, and rabbit_khepri:can_join would accept a join request from a node that is already a member

Author: SimonUnge

deps/rabbit/src/rabbit_mnesia.erl

@@ -178,9 +178,15 @@ can_join_cluster(DiscoveryNode) ->
                     rabbit_log:info("Asked to join a cluster but already a member of it: ~tp", [ClusterNodes]),
                     {ok, already_member};
                 false ->
-                    Msg = format_inconsistent_cluster_message(DiscoveryNode, node()),
-                    rabbit_log:error(Msg),
-                    {error, {inconsistent_cluster, Msg}}
+                    %% Leave cluster and try again. Limit the number of times?
+                    %% Also this is perhaps a weird place to do this, better to do
+                    %% something similar in rabbit_db_cluster:join/2?
+                    rabbit_log:info("Mnesia: node ~tp thinks it's clustered "
+                                    "with node ~tp, but ~tp disagrees. ~tp will ask "
+                                    "to leave the cluster and try again.",
+                                    [DiscoveryNode, node(), node(), node()]),
+                    leave_cluster(rabbit_nodes:nodes_excl_me(ClusterNodes)),
+                    can_join_cluster(DiscoveryNode)
             end
     end.
 
@@ -924,14 +930,14 @@ remove_node_if_mnesia_running(Node) ->
     end.
 
 leave_cluster() ->
-    case rabbit_nodes:nodes_excl_me(cluster_nodes(all)) of
-        []       -> ok;
-        AllNodes -> case lists:any(fun leave_cluster/1, AllNodes) of
-                        true  -> ok;
-                        false -> e(no_running_cluster_nodes)
-                    end
-    end.
-
+    leave_cluster(rabbit_nodes:nodes_excl_me(cluster_nodes(all))).
+leave_cluster([]) ->
+    ok;
+leave_cluster(Nodes) when is_list(Nodes)  ->
+    case lists:any(fun leave_cluster/1, Nodes) of
+        true  -> ok;
+        false -> e(no_running_cluster_nodes)
+    end;
 leave_cluster(Node) ->
     case rpc:call(Node,
                   rabbit_mnesia, remove_node_if_mnesia_running, [node()]) of