Merge branch 'reduce-mnesia-contention-when-nodes-restart-v3.7.x' into reduce-mnesia-contention-when-nodes-restart-master

4 files changed, 65 insertions, 45 deletions

diff --git a/src/rabbit_amqqueue.erl b/src/rabbit_amqqueue.erl
index b9f1ba3631..ac79d56358 100644
--- a/src/rabbit_amqqueue.erl
+++ b/src/rabbit_amqqueue.erl
@@ -963,12 +963,7 @@ resume(QPid, ChPid) -> delegate:invoke_no_result(QPid, {gen_server2, cast, [{res
 
 internal_delete1(QueueName, OnlyDurable) ->
     ok = mnesia:delete({rabbit_queue, QueueName}),
-    %% this 'guarded' delete prevents unnecessary writes to the mnesia
-    %% disk log
-    case mnesia:wread({rabbit_durable_queue, QueueName}) of
-        []  -> ok;
-        [_] -> ok = mnesia:delete({rabbit_durable_queue, QueueName})
-    end,
+    mnesia:delete({rabbit_durable_queue, QueueName}),
     %% we want to execute some things, as decided by rabbit_exchange,
     %% after the transaction.
     rabbit_binding:remove_for_destination(QueueName, OnlyDurable).
@@ -1117,36 +1112,70 @@ maybe_clear_recoverable_node(Node,
     end.
 
 on_node_down(Node) ->
-    rabbit_misc:execute_mnesia_tx_with_tail(
-      fun () -> QsDels =
-                    qlc:e(qlc:q([{QName, delete_queue(QName)} ||
-                                  #amqqueue{name = QName, pid = Pid} =
-                                  Q <- mnesia:table(rabbit_queue),
-                                    node(Pid) == Node andalso
-                                    not rabbit_mnesia:is_process_alive(Pid) andalso
-                                    (not rabbit_amqqueue:is_mirrored(Q) orelse
-                                     rabbit_amqqueue:is_dead_exclusive(Q))])),
-                {Qs, Dels} = lists:unzip(QsDels),
-                T = rabbit_binding:process_deletions(
-                      lists:foldl(fun rabbit_binding:combine_deletions/2,
-                                  rabbit_binding:new_deletions(), Dels),
-                      ?INTERNAL_USER),
-                fun () ->
-                        T(),
-                        lists:foreach(
-                          fun(QName) ->
-                                  rabbit_core_metrics:queue_deleted(QName),
-                                  ok = rabbit_event:notify(queue_deleted,
-                                                           [{name, QName},
-                                                            {user, ?INTERNAL_USER}])
-                          end, Qs)
-                end
-      end).
+    {QueueNames, QueueDeletions} = delete_queues_on_node_down(Node),
+    notify_queue_binding_deletions(QueueDeletions),
+    rabbit_core_metrics:queues_deleted(QueueNames),
+    notify_queues_deleted(QueueNames),
+    ok.
+
+delete_queues_on_node_down(Node) ->
+    lists:unzip(lists:flatten([
+        rabbit_misc:execute_mnesia_transaction(
+          fun () -> [{Queue, delete_queue(Queue)} || Queue <- Queues] end
+        ) || Queues <- partition_queues(queues_to_delete_when_node_down(Node))
+    ])).
 
 delete_queue(QueueName) ->
     ok = mnesia:delete({rabbit_queue, QueueName}),
     rabbit_binding:remove_transient_for_destination(QueueName).
 
+% If there are many queues and we delete them all in a single Mnesia transaction,
+% this can block all other Mnesia operations for a really long time.
+% In situations where a node wants to (re-)join a cluster,
+% Mnesia won't be able to sync on the new node until this operation finishes.
+% As a result, we want to have multiple Mnesia transactions so that other
+% operations can make progress in between these queue delete transactions.
+%
+% 10 queues per Mnesia transaction is an arbitrary number, but it seems to work OK with 50k queues per node.
+partition_queues([Q0,Q1,Q2,Q3,Q4,Q5,Q6,Q7,Q8,Q9 | T]) ->
+    [[Q0,Q1,Q2,Q3,Q4,Q5,Q6,Q7,Q8,Q9] | partition_queues(T)];
+partition_queues(T) ->
+    [T].
+
+queues_to_delete_when_node_down(NodeDown) ->
+    rabbit_misc:execute_mnesia_transaction(fun () ->
+        qlc:e(qlc:q([QName ||
+            #amqqueue{name = QName, pid = Pid} = Q <- mnesia:table(rabbit_queue),
+                node(Pid) == NodeDown andalso
+                not rabbit_mnesia:is_process_alive(Pid) andalso
+                (not rabbit_amqqueue:is_mirrored(Q) orelse
+                rabbit_amqqueue:is_dead_exclusive(Q))]
+        ))
+    end).
+
+notify_queue_binding_deletions(QueueDeletions) ->
+    rabbit_misc:execute_mnesia_tx_with_tail(
+        fun() ->
+            rabbit_binding:process_deletions(
+                lists:foldl(
+                    fun rabbit_binding:combine_deletions/2,
+                    rabbit_binding:new_deletions(),
+                    QueueDeletions
+                ),
+                ?INTERNAL_USER
+            )
+        end
+    ).
+
+notify_queues_deleted(QueueDeletions) ->
+    lists:foreach(
+      fun(Queue) ->
+              ok = rabbit_event:notify(queue_deleted,
+                                       [{name, Queue},
+                                        {user, ?INTERNAL_USER}])
+      end,
+      QueueDeletions).
+
 pseudo_queue(QueueName, Pid) ->
     #amqqueue{name         = QueueName,
               durable      = false,
diff --git a/src/rabbit_binding.erl b/src/rabbit_binding.erl
index e4d9e64d6b..7498d6b765 100644
--- a/src/rabbit_binding.erl
+++ b/src/rabbit_binding.erl
@@ -331,13 +331,8 @@ binding_action(Binding = #binding{source      = SrcName,
               Fun(Src, Dst, Binding#binding{args = SortedArgs})
       end, ErrFun).
 
-delete_object(Tab, Record, LockKind) ->
-    %% this 'guarded' delete prevents unnecessary writes to the mnesia
-    %% disk log
-    case mnesia:match_object(Tab, Record, LockKind) of
-        []  -> ok;
-        [_] -> mnesia:delete_object(Tab, Record, LockKind)
-    end.
+delete_object(Table, Record, LockKind) ->
+    mnesia:delete_object(Table, Record, LockKind).
 
 sync_route(Route, true, true, Fun) ->
     ok = Fun(rabbit_durable_route, Route, write),
diff --git a/src/rabbit_exchange.erl b/src/rabbit_exchange.erl
index cc2797489d..c7a849ce2e 100644
--- a/src/rabbit_exchange.erl
+++ b/src/rabbit_exchange.erl
@@ -497,14 +497,9 @@ conditional_delete(X = #exchange{name = XName}, OnlyDurable) ->
     end.
 
 unconditional_delete(X = #exchange{name = XName}, OnlyDurable) ->
-    %% this 'guarded' delete prevents unnecessary writes to the mnesia
-    %% disk log
-    case mnesia:wread({rabbit_durable_exchange, XName}) of
-        []  -> ok;
-        [_] -> ok = mnesia:delete({rabbit_durable_exchange, XName})
-    end,
     ok = mnesia:delete({rabbit_exchange, XName}),
     ok = mnesia:delete({rabbit_exchange_serial, XName}),
+    mnesia:delete({rabbit_durable_exchange, XName}),
     Bindings = rabbit_binding:remove_for_source(XName),
     {deleted, X, Bindings, rabbit_binding:remove_for_destination(
                              XName, OnlyDurable)}.
diff --git a/src/rabbit_node_monitor.erl b/src/rabbit_node_monitor.erl
index 565676af3c..4a362eb8a2 100644
--- a/src/rabbit_node_monitor.erl
+++ b/src/rabbit_node_monitor.erl
@@ -37,6 +37,7 @@
          alive_nodes/1, alive_rabbit_nodes/1]).
 
 -define(SERVER, ?MODULE).
+-define(NODE_REPLY_TIMEOUT, 5000).
 -define(RABBIT_UP_RPC_TIMEOUT, 2000).
 -define(RABBIT_DOWN_PING_INTERVAL, 1000).
 
@@ -181,7 +182,7 @@ partitions() ->
     gen_server:call(?SERVER, partitions, infinity).
 
 partitions(Nodes) ->
-    {Replies, _} = gen_server:multi_call(Nodes, ?SERVER, partitions, infinity),
+    {Replies, _} = gen_server:multi_call(Nodes, ?SERVER, partitions, ?NODE_REPLY_TIMEOUT),
     Replies.
 
 status(Nodes) ->