Drop head after changing a policy to drop-head. Clarify TODOs

Author: Daniil Fedotov

src/rabbit_amqqueue_process.erl

@@ -428,8 +428,14 @@ init_max_bytes(MaxBytes, State) ->
 init_overflow(undefined, State) ->
     State;
 init_overflow(Overflow, State) ->
-    %% TODO maybe drop head
-    State#q{overflow = binary_to_existing_atom(Overflow, utf8)}.
+    OverflowVal = binary_to_existing_atom(Overflow, utf8),
+    case OverflowVal of
+        'drop-head' ->
+            {_Dropped, State1} = maybe_drop_head(State#q{overflow = OverflowVal}),
+            State1;
+        _ ->
+            State#q{overflow = OverflowVal}
+    end.
 
 init_queue_mode(undefined, State) ->
     State;

src/rabbit_channel.erl

@@ -1879,7 +1879,8 @@ send_confirms_and_nacks(State = #ch{tx = none, confirmed = C, rejected = R}) ->
                                  [MsgSeqNo | MSNs]
                          end, [], lists:append(C)),
                    State1 = send_confirms(ConfirmMsgSeqNos, State#ch{confirmed = []}),
-                   %% TODO: msg seq nos, same as for confirms.
+                   %% TODO: msg seq nos, same as for confirms. Need to implement
+                   %% nack rates first.
                    send_nacks(lists:append(R), State1#ch{rejected = []});
         pausing -> State
     end;

src/rabbit_mirror_queue_slave.erl

@@ -302,7 +302,8 @@ handle_cast({deliver, Delivery = #delivery{sender = Sender, flow = Flow}, true},
     %% We are acking messages to the channel process that sent us
     %% the message delivery. See
     %% rabbit_amqqueue_process:handle_ch_down for more info.
-    %% TODO: reject publishes
+    %% If message is rejected by the master, the publish will be nacked
+    %% even if slaves confirm it. No need to check for length here.
     maybe_flow_ack(Sender, Flow),
     noreply(maybe_enqueue_message(Delivery, State));