refactor: disentangle head dropping and publishing

1 files changed, 12 insertions, 17 deletions

diff --git a/src/rabbit_amqqueue_process.erl b/src/rabbit_amqqueue_process.erl
index a4a30021..77514383 100644
--- a/src/rabbit_amqqueue_process.erl
+++ b/src/rabbit_amqqueue_process.erl
@@ -560,7 +560,7 @@ attempt_delivery(Delivery = #delivery{sender = SenderPid, message = Message},
             {false, State#q{backing_queue_state = BQS1}}
     end.
 
-deliver_or_enqueue(Delivery = #delivery{message = Message},
+deliver_or_enqueue(Delivery = #delivery{message = Message, sender = SenderPid},
                    Delivered, State) ->
     {Confirm, State1} = send_or_record_confirm(Delivery, State),
     Props = message_properties(Message, Confirm, State),
@@ -571,28 +571,23 @@ deliver_or_enqueue(Delivery = #delivery{message = Message},
         {false, State2 = #q{ttl = 0, dlx = undefined}} ->
             discard(Delivery, State2);
         {false, State2} ->
-            BQS1 = publish_max(Delivery, Props, Delivered, State2),
+            State3 = #q{backing_queue = BQ, backing_queue_state = BQS} =
+                maybe_drop_head(State2),
+            BQS1 = BQ:publish(Message, Props, Delivered, SenderPid, BQS),
             ensure_ttl_timer(Props#message_properties.expiry,
-                             State2#q{backing_queue_state = BQS1})
+                             State3#q{backing_queue_state = BQS1})
     end.
 
-publish_max(#delivery{message = Message,
-                      sender  = SenderPid},
-            Props, Delivered, #q{backing_queue       = BQ,
-                                 backing_queue_state = BQS,
-                                 max_length          = undefined}) ->
-    BQ:publish(Message, Props, Delivered, SenderPid, BQS);
-publish_max(#delivery{message    = Message,
-                      msg_seq_no = MsgSeqNo,
-                      sender     = SenderPid},
-            Props, Delivered, #q{backing_queue       = BQ,
-                                 backing_queue_state = BQS,
-                                 max_length          = MaxLen}) ->
+maybe_drop_head(State = #q{max_length = undefined}) ->
+    State;
+maybe_drop_head(State = #q{max_length          = MaxLen,
+                           backing_queue       = BQ,
+                           backing_queue_state = BQS}) ->
     case BQ:len(BQS) >= MaxLen of
         true ->  {{Msg, _IsDelivered, AckTag}, BQS1} = BQ:fetch(true, BQS),
                  (dead_letter_fun(maxlen))([{Msg, AckTag}]),
-                 BQ:publish(Message, Props, Delivered, SenderPid, BQS1);
-        false -> BQ:publish(Message, Props, Delivered, SenderPid, BQS)
+                 State#q{backing_queue_state = BQS1};
+        false -> State
     end.
 
 requeue_and_run(AckTags, State = #q{backing_queue       = BQ,