But Matthias points out that we can avoid the three-way-ness by changing the meaning of non-forced clustering so that you must only have to contact *one* disc node. This seems to work.

2 files changed, 17 insertions, 34 deletions

diff --git a/src/rabbit_mnesia.erl b/src/rabbit_mnesia.erl
index 138dad5e..75ad3dc8 100644
--- a/src/rabbit_mnesia.erl
+++ b/src/rabbit_mnesia.erl
@@ -46,8 +46,7 @@
 -spec(dir/0 :: () -> file:filename()).
 -spec(ensure_mnesia_dir/0 :: () -> 'ok').
 -spec(init/0 :: () -> 'ok').
--spec(init_db/3 :: ([node()], 'all' | 'some' | 'none',
-                    rabbit_misc:thunk('ok')) -> 'ok').
+-spec(init_db/3 :: ([node()], boolean(), rabbit_misc:thunk('ok')) -> 'ok').
 -spec(is_db_empty/0 :: () -> boolean()).
 -spec(cluster/1 :: ([node()]) -> 'ok').
 -spec(force_cluster/1 :: ([node()]) -> 'ok').
@@ -100,10 +99,7 @@ init() ->
     ensure_mnesia_running(),
     ensure_mnesia_dir(),
     Nodes = read_cluster_nodes_config(),
-    ok = init_db(Nodes, case should_be_disc_node(Nodes) of
-                            true  -> none;
-                            false -> some
-                        end),
+    ok = init_db(Nodes, should_be_disc_node(Nodes)),
     %% We intuitively expect the global name server to be synced when
     %% Mnesia is up. In fact that's not guaranteed to be the case - let's
     %% make it so.
@@ -178,10 +174,7 @@ cluster(ClusterNodes, Force) ->
     %% Join the cluster
     start_mnesia(),
     try
-        ok = init_db(ClusterNodes, case Force of
-                                       true  -> none;
-                                       false -> all
-                                   end),
+        ok = init_db(ClusterNodes, Force),
         ok = create_cluster_nodes_config(ClusterNodes)
     after
         stop_mnesia()
@@ -507,9 +500,9 @@ delete_previously_running_nodes() ->
                                           FileName, Reason}})
     end.
 
-init_db(ClusterNodes, RequiredNodes) ->
+init_db(ClusterNodes, Force) ->
     init_db(
-      ClusterNodes, RequiredNodes,
+      ClusterNodes, Force,
       fun () ->
               case rabbit_upgrade:maybe_upgrade_local() of
                   ok                    -> ok;
@@ -521,32 +514,22 @@ init_db(ClusterNodes, RequiredNodes) ->
 
 %% Take a cluster node config and create the right kind of node - a
 %% standalone disk node, or disk or ram node connected to the
-%% specified cluster nodes. RequiredDiscNodes determines how many disc
-%% nodes must be up for us to succeed - 'none' (used when forcing
-%% cluster or starting a disc node), 'some' (used when starting a RAM
-%% node) or 'all' (used when non-forced clustering).
-init_db(ClusterNodes, RequiredDiscNodes, SecondaryPostMnesiaFun) ->
+%% specified cluster nodes.  If Force is false, don't allow
+%% connections if all disc nodes are offline and we are a RAM node.
+init_db(ClusterNodes, Force, SecondaryPostMnesiaFun) ->
     UClusterNodes = lists:usort(ClusterNodes),
     ProperClusterNodes = UClusterNodes -- [node()],
     case mnesia:change_config(extra_db_nodes, ProperClusterNodes) of
         {ok, Nodes} ->
-            FailedDiscNodes = ProperClusterNodes -- Nodes,
-            OK = case {FailedDiscNodes, Nodes, RequiredDiscNodes} of
-                     {[], _,  all}  -> true;
-                     {_,  _,  all}  -> false;
-                     {_,  [], some} -> false;
-                     {_,  _,  some} -> true;
-                     {_,  _,  none} -> true
-                 end,
-            case OK of
-                true  -> ok;
-                false -> throw({error, {failed_to_cluster_with,
-                                        FailedDiscNodes,
-                                        "Mnesia could not connect "
-                                        "to some nodes."}})
+            case {Nodes, Force} of
+                {[], false} -> throw({error, {failed_to_cluster_with,
+                                              ProperClusterNodes,
+                                              "Mnesia could not connect "
+                                              "to any disc nodes."}});
+                _           -> ok
             end,
-            WantDiscNode = should_be_disc_node(ClusterNodes),
             WasDiscNode = is_disc_node(),
+            WantDiscNode = should_be_disc_node(ClusterNodes),
             %% We create a new db (on disk, or in ram) in the first
             %% two cases and attempt to upgrade the in the other two
             case {Nodes, WasDiscNode, WantDiscNode} of
@@ -763,7 +746,7 @@ reset(Force) ->
                 try
                     %% Force=true here so that reset still works when clustered
                     %% with a node which is down
-                    ok = init_db(read_cluster_nodes_config(), none),
+                    ok = init_db(read_cluster_nodes_config(), true),
                     {all_clustered_nodes() -- [Node],
                      running_clustered_nodes() -- [Node]}
                 after
diff --git a/src/rabbit_upgrade.erl b/src/rabbit_upgrade.erl
index 776da90d..717d94a8 100644
--- a/src/rabbit_upgrade.erl
+++ b/src/rabbit_upgrade.erl
@@ -223,7 +223,7 @@ secondary_upgrade(AllNodes) ->
                        false -> AllNodes -- [node()]
                    end,
     rabbit_misc:ensure_ok(mnesia:start(), cannot_start_mnesia),
-    ok = rabbit_mnesia:init_db(ClusterNodes, none, fun () -> ok end),
+    ok = rabbit_mnesia:init_db(ClusterNodes, true, fun () -> ok end),
     ok = rabbit_version:record_desired_for_scope(mnesia),
     ok.