merge default into bug19375

2 files changed, 32 insertions, 5 deletions

diff --git a/src/rabbit_amqqueue.erl b/src/rabbit_amqqueue.erl
index fbe146e8..a9f2f390 100644
--- a/src/rabbit_amqqueue.erl
+++ b/src/rabbit_amqqueue.erl
@@ -391,7 +391,8 @@ check_declare_arguments(QueueName, Args) ->
     Checks = [{<<"x-expires">>,                 fun check_expires_arg/2},
               {<<"x-message-ttl">>,             fun check_message_ttl_arg/2},
               {<<"x-dead-letter-exchange">>,    fun check_string_arg/2},
-              {<<"x-dead-letter-routing-key">>, fun check_dlxrk_arg/2}],
+              {<<"x-dead-letter-routing-key">>, fun check_dlxrk_arg/2},
+              {<<"x-max-length">>,              fun check_max_length_arg/2}],
     [case rabbit_misc:table_lookup(Args, Key) of
          undefined -> ok;
          TypeVal   -> case Fun(TypeVal, Args) of
@@ -414,6 +415,13 @@ check_int_arg({Type, _}, _) ->
         false -> {error, {unacceptable_type, Type}}
     end.
 
+check_max_length_arg({Type, Val}, Args) ->
+    case check_int_arg({Type, Val}, Args) of
+        ok when Val >= 0 -> ok;
+        ok               -> {error, {value_negative, Val}};
+        Error            -> Error
+    end.
+
 check_expires_arg({Type, Val}, Args) ->
     case check_int_arg({Type, Val}, Args) of
         ok when Val == 0 -> {error, {value_zero, Val}};
diff --git a/src/rabbit_amqqueue_process.erl b/src/rabbit_amqqueue_process.erl
index 35f0b816..004180db 100644
--- a/src/rabbit_amqqueue_process.erl
+++ b/src/rabbit_amqqueue_process.erl
@@ -54,7 +54,8 @@
             delayed_stop,
             queue_monitors,
             dlx,
-            dlx_routing_key
+            dlx_routing_key,
+            max_length
            }).
 
 -record(consumer, {tag, ack_required}).
@@ -240,7 +241,8 @@ process_args(State = #q{q = #amqqueue{arguments = Arguments}}) ->
       [{<<"x-expires">>,                 fun init_expires/2},
        {<<"x-dead-letter-exchange">>,    fun init_dlx/2},
        {<<"x-dead-letter-routing-key">>, fun init_dlx_routing_key/2},
-       {<<"x-message-ttl">>,             fun init_ttl/2}]).
+       {<<"x-message-ttl">>,             fun init_ttl/2},
+       {<<"x-max-length">>,              fun init_max_length/2}]).
 
 init_expires(Expires, State) -> ensure_expiry_timer(State#q{expires = Expires}).
 
@@ -252,6 +254,9 @@ init_dlx(DLX, State = #q{q = #amqqueue{name = QName}}) ->
 init_dlx_routing_key(RoutingKey, State) ->
     State#q{dlx_routing_key = RoutingKey}.
 
+init_max_length(MaxLen, State) ->
+    State#q{max_length = MaxLen}.
+
 terminate_shutdown(Fun, State) ->
     State1 = #q{backing_queue_state = BQS} =
         stop_sync_timer(stop_rate_timer(State)),
@@ -545,10 +550,24 @@ deliver_or_enqueue(Delivery = #delivery{message = Message, sender = SenderPid},
         %% The next one is an optimisation
         {false, State2 = #q{ttl = 0, dlx = undefined}} ->
             discard(Delivery, State2);
-        {false, State2 = #q{backing_queue = BQ, backing_queue_state = BQS}} ->
+        {false, 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.
+
+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}]),
+                 State#q{backing_queue_state = BQS1};
+        false -> State
     end.
 
 requeue_and_run(AckTags, State = #q{backing_queue       = BQ,