Merge pull request #3641 from rabbitmq/mergify/bp/v3.9.x/pr-3631

Use erlang:system_info(creation) as GUID (backport #3631)

Author: michaelklishin

deps/rabbit/src/rabbit_amqqueue.erl

@@ -1905,7 +1905,11 @@ maybe_clear_recoverable_node(Node, Q) ->
 -spec on_node_down(node()) -> 'ok'.
 
 on_node_down(Node) ->
-    {QueueNames, QueueDeletions} = delete_queues_on_node_down(Node),
+    {Time, {QueueNames, QueueDeletions}} = timer:tc(fun() -> delete_queues_on_node_down(Node) end),
+    case length(QueueNames) of
+        0 -> ok;
+        _ -> rabbit_log:info("~p transient queues from an old incarnation of node ~p deleted in ~fs", [length(QueueNames), Node, Time/1000000])
+    end,
     notify_queue_binding_deletions(QueueDeletions),
     rabbit_core_metrics:queues_deleted(QueueNames),
     notify_queues_deleted(QueueNames),

deps/rabbit/src/rabbit_node_monitor.erl

@@ -366,7 +366,7 @@ init([]) ->
     {ok, ensure_keepalive_timer(#state{monitors    = Monitors,
                                        subscribers = pmon:new(),
                                        partitions  = [],
-                                       guid        = rabbit_guid:gen(),
+                                       guid        = erlang:system_info(creation),
                                        node_guids  = maps:new(),
                                        autoheal    = rabbit_autoheal:init()})}.
 
@@ -416,6 +416,13 @@ handle_cast(notify_node_up, State = #state{guid = GUID}) ->
 %% disconnected, it would become a minority, pause, realise it's not
 %% in a minority any more, and come back, still partitioned (albeit no
 %% longer partially).
+%%
+%% UPDATE: The GUID is actually not a GUID anymore - it is the value
+%% returned by erlang:system_info(creation). This prevent false-positives
+%% in a situation when a node is restarted (Erlang VM is up) but the rabbit
+%% app is not yet up. The GUID was only generated and announced upon rabbit
+%% startup; creation is available immediately. Therefore we can tell that
+%% the node was restarted, before it announces the new value.
 %% ----------------------------------------------------------------------------
 
 handle_cast({node_up, Node, NodeType, GUID},
@@ -435,15 +442,18 @@ handle_cast({check_partial_partition, Node, Rep, NodeGUID, MyGUID, RepGUID},
         maps:find(Node, GUIDs) =:= {ok, NodeGUID} of
         true  -> spawn_link( %%[1]
                    fun () ->
-                           case rpc:call(Node, rabbit, is_running, []) of
+                           case rpc:call(Node, erlang, system_info, [creation]) of
                                {badrpc, _} -> ok;
-                               _           ->
+                               NodeGUID ->
                                    rabbit_log:warning("Received a 'DOWN' message"
                                                       " from ~p but still can"
                                                       " communicate with it ",
                                                       [Node]),
                                    cast(Rep, {partial_partition,
-                                                         Node, node(), RepGUID})
+                                                         Node, node(), RepGUID});
+                                _ ->
+                                   rabbit_log:warning("Node ~p was restarted", [Node]),
+                                   ok
                            end
                    end);
         false -> ok