cluster_cp_mode

2 files changed, 32 insertions, 0 deletions

diff --git a/src/rabbit_mnesia.erl b/src/rabbit_mnesia.erl
index c39e898cec..ecb03f54ba 100644
--- a/src/rabbit_mnesia.erl
+++ b/src/rabbit_mnesia.erl
@@ -26,6 +26,7 @@
 
          status/0,
          is_clustered/0,
+         majority/0,
          cluster_nodes/1,
          node_type/0,
          dir/0,
@@ -67,6 +68,7 @@
 -spec(status/0 :: () -> [{'nodes', [{node_type(), [node()]}]} |
                          {'running_nodes', [node()]} |
                          {'partitions', [{node(), [node()]}]}]).
+-spec(majority/0 :: () -> boolean()).
 -spec(is_clustered/0 :: () -> boolean()).
 -spec(cluster_nodes/1 :: ('all' | 'disc' | 'ram' | 'running') -> [node()]).
 -spec(node_type/0 :: () -> node_type()).
@@ -338,6 +340,10 @@ status() ->
             false -> []
         end.
 
+majority() ->
+    ensure_mnesia_running(),
+    (length(cluster_nodes(running)) / length(cluster_nodes(all))) > 0.5.
+
 mnesia_partitions(Nodes) ->
     {Replies, _BadNodes} = rpc:multicall(
                              Nodes, rabbit_node_monitor, partitions, []),
diff --git a/src/rabbit_node_monitor.erl b/src/rabbit_node_monitor.erl
index 71c2c80ac7..7b7fed5ce6 100644
--- a/src/rabbit_node_monitor.erl
+++ b/src/rabbit_node_monitor.erl
@@ -250,6 +250,10 @@ handle_info({mnesia_system_event,
                     ordsets:add_element(Node, ordsets:from_list(Partitions))),
     {noreply, State#state{partitions = Partitions1}};
 
+handle_info({mnesia_system_event, {mnesia_down, _Node}}, State) ->
+    handle_dead_according_to_mnesia_rabbit(),
+    {noreply, State};
+
 handle_info(_Info, State) ->
     {noreply, State}.
 
@@ -272,6 +276,28 @@ handle_dead_rabbit(Node) ->
     ok = rabbit_alarm:on_node_down(Node),
     ok = rabbit_mnesia:on_node_down(Node).
 
+%% Since we will be introspecting the cluster in response to this, we
+%% must only do so based on Mnesia having noticed the other node being
+%% down - otherwise we have a race.
+handle_dead_according_to_mnesia_rabbit() ->
+    case application:get_env(rabbit, cluster_cp_mode) of
+        {ok, true}  -> case rabbit_mnesia:majority() of
+                           true  -> ok;
+                           false -> stop_and_halt()
+                       end;
+        {ok, false} -> ok
+    end,
+    ok.
+
+stop_and_halt() ->
+    rabbit_log:warning("Cluster minority status detected - stopping~n", []),
+    spawn(fun () ->
+                  %% If our group leader is inside an application we are about
+                  %% to stop, application:stop/1 does not return.
+                  group_leader(whereis(init), self()),
+                  rabbit:stop_and_halt()
+          end).
+
 handle_live_rabbit(Node) ->
     ok = rabbit_alarm:on_node_up(Node),
     ok = rabbit_mnesia:on_node_up(Node).