merge bug24980 into default

17 files changed, 309 insertions, 179 deletions

diff --git a/Makefile b/Makefile
index c63e3dfd..bf33b931 100644
--- a/Makefile
+++ b/Makefile
@@ -162,7 +162,7 @@ $(BASIC_PLT): $(BEAM_TARGETS)
 	else \
 	    dialyzer --output_plt $@ --build_plt \
 		--apps erts kernel stdlib compiler sasl os_mon mnesia tools \
-		  public_key crypto ssl; \
+		  public_key crypto ssl xmerl; \
 	fi
 
 clean:
diff --git a/docs/rabbitmqctl.1.xml b/docs/rabbitmqctl.1.xml
index c7069aed..bbd2fe5b 100644
--- a/docs/rabbitmqctl.1.xml
+++ b/docs/rabbitmqctl.1.xml
@@ -465,8 +465,7 @@
               synchronise itself. The queue will block while
               synchronisation takes place (all publishers to and
               consumers from the queue will block). The queue must be
-              mirrored, and must not have any pending unacknowledged
-              messages for this command to succeed.
+              mirrored for this command to succeed.
             </para>
             <para>
               Note that unsynchronised queues from which messages are
diff --git a/src/rabbit.erl b/src/rabbit.erl
index 641f81c0..0e6c970f 100644
--- a/src/rabbit.erl
+++ b/src/rabbit.erl
@@ -540,6 +540,9 @@ sort_boot_steps(UnsortedSteps) ->
                end])
     end.
 
+-ifdef(use_specs).
+-spec(boot_error/2 :: (term(), not_available | [tuple()]) -> no_return()).
+-endif.
 boot_error(Term={error, {timeout_waiting_for_tables, _}}, _Stacktrace) ->
     AllNodes = rabbit_mnesia:cluster_nodes(all),
     {Err, Nodes} =
@@ -559,13 +562,15 @@ boot_error(Reason, Stacktrace) ->
     Args = [Reason, log_location(kernel), log_location(sasl)],
     boot_error(Reason, Fmt, Args, Stacktrace).
 
+-ifdef(use_specs).
+-spec(boot_error/4 :: (term(), string(), [any()], not_available | [tuple()])
+                      -> no_return()).
+-endif.
+boot_error(Reason, Fmt, Args, not_available) ->
+    basic_boot_error(Reason, Fmt, Args);
 boot_error(Reason, Fmt, Args, Stacktrace) ->
-    case Stacktrace of
-        not_available -> basic_boot_error(Reason, Fmt, Args);
-        _             -> basic_boot_error(Reason, Fmt ++
-                                              "Stack trace:~n   ~p~n~n",
-                                          Args ++ [Stacktrace])
-    end.
+    basic_boot_error(Reason, Fmt ++ "Stack trace:~n   ~p~n~n",
+                     Args ++ [Stacktrace]).
 
 basic_boot_error(Reason, Format, Args) ->
     io:format("~n~nBOOT FAILED~n===========~n~n" ++ Format, Args),
diff --git a/src/rabbit_amqqueue.erl b/src/rabbit_amqqueue.erl
index 2477b891..21b6bb92 100644
--- a/src/rabbit_amqqueue.erl
+++ b/src/rabbit_amqqueue.erl
@@ -174,8 +174,7 @@
         (rabbit_types:amqqueue(), rabbit_types:amqqueue()) -> 'ok').
 -spec(start_mirroring/1 :: (pid()) -> 'ok').
 -spec(stop_mirroring/1 :: (pid()) -> 'ok').
--spec(sync_mirrors/1 :: (pid()) ->
-    'ok' | rabbit_types:error('pending_acks' | 'not_mirrored')).
+-spec(sync_mirrors/1 :: (pid()) -> 'ok' | rabbit_types:error('not_mirrored')).
 -spec(cancel_sync_mirrors/1 :: (pid()) -> 'ok' | {'ok', 'not_syncing'}).
 
 -endif.
diff --git a/src/rabbit_amqqueue_process.erl b/src/rabbit_amqqueue_process.erl
index 0a07a005..2795e317 100644
--- a/src/rabbit_amqqueue_process.erl
+++ b/src/rabbit_amqqueue_process.erl
@@ -1163,7 +1163,7 @@ handle_call({requeue, AckTags, ChPid}, From, State) ->
     noreply(requeue(AckTags, ChPid, State));
 
 handle_call(sync_mirrors, _From,
-            State = #q{backing_queue       = rabbit_mirror_queue_master = BQ,
+            State = #q{backing_queue       = rabbit_mirror_queue_master,
                        backing_queue_state = BQS}) ->
     S = fun(BQSN) -> State#q{backing_queue_state = BQSN} end,
     HandleInfo = fun (Status) ->
@@ -1179,13 +1179,9 @@ handle_call(sync_mirrors, _From,
                           State, #q.stats_timer,
                           fun() -> emit_stats(State#q{status = Status}) end)
                 end,
-    case BQ:depth(BQS) - BQ:len(BQS) of
-        0 -> case rabbit_mirror_queue_master:sync_mirrors(
-                    HandleInfo, EmitStats, BQS) of
-                 {ok, BQS1}           -> reply(ok, S(BQS1));
-                 {stop, Reason, BQS1} -> {stop, Reason, S(BQS1)}
-             end;
-        _ -> reply({error, pending_acks}, State)
+    case rabbit_mirror_queue_master:sync_mirrors(HandleInfo, EmitStats, BQS) of
+        {ok, BQS1}           -> reply(ok, S(BQS1));
+        {stop, Reason, BQS1} -> {stop, Reason, S(BQS1)}
     end;
 
 handle_call(sync_mirrors, _From, State) ->
diff --git a/src/rabbit_backing_queue.erl b/src/rabbit_backing_queue.erl
index 99b5946e..4245f7e2 100644
--- a/src/rabbit_backing_queue.erl
+++ b/src/rabbit_backing_queue.erl
@@ -71,10 +71,14 @@
 %% content.
 -callback delete_and_terminate(any(), state()) -> state().
 
-%% Remove all messages in the queue, but not messages which have been
-%% fetched and are pending acks.
+%% Remove all 'fetchable' messages from the queue, i.e. all messages
+%% except those that have been fetched already and are pending acks.
 -callback purge(state()) -> {purged_msg_count(), state()}.
 
+%% Remove all messages in the queue which have been fetched and are
+%% pending acks.
+-callback purge_acks(state()) -> state().
+
 %% Publish a message.
 -callback publish(rabbit_types:basic_message(),
                   rabbit_types:message_properties(), boolean(), pid(),
@@ -164,7 +168,7 @@
 %% results, leaving the queue undisturbed.
 -callback fold(fun((rabbit_types:basic_message(),
                     rabbit_types:message_properties(),
-                    A) -> {('stop' | 'cont'), A}),
+                    boolean(), A) -> {('stop' | 'cont'), A}),
                A, state()) -> {A, state()}.
 
 %% How long is my queue?
@@ -226,7 +230,7 @@
 
 behaviour_info(callbacks) ->
     [{start, 1}, {stop, 0}, {init, 3}, {terminate, 2},
-     {delete_and_terminate, 2}, {purge, 1}, {publish, 5},
+     {delete_and_terminate, 2}, {purge, 1}, {purge_acks, 1}, {publish, 5},
      {publish_delivered, 4}, {discard, 3}, {drain_confirmed, 1},
      {dropwhile, 2}, {fetchwhile, 4},
      {fetch, 2}, {ack, 2}, {requeue, 2}, {ackfold, 4}, {fold, 3}, {len, 1},
diff --git a/src/rabbit_channel.erl b/src/rabbit_channel.erl
index 88e3dfc5..614e307c 100644
--- a/src/rabbit_channel.erl
+++ b/src/rabbit_channel.erl
@@ -284,7 +284,8 @@ handle_cast(ready_for_close, State = #ch{state      = closing,
     ok = rabbit_writer:send_command_sync(WriterPid, #'channel.close_ok'{}),
     {stop, normal, State};
 
-handle_cast(terminate, State) ->
+handle_cast(terminate, State = #ch{writer_pid = WriterPid}) ->
+    ok = rabbit_writer:flush(WriterPid),
     {stop, normal, State};
 
 handle_cast({command, #'basic.consume_ok'{consumer_tag = ConsumerTag} = Msg},
@@ -412,8 +413,14 @@ handle_exception(Reason, State = #ch{protocol   = Protocol,
             {stop, normal, State1}
     end.
 
+-ifdef(use_specs).
+-spec(precondition_failed/1 :: (string()) -> no_return()).
+-endif.
 precondition_failed(Format) -> precondition_failed(Format, []).
 
+-ifdef(use_specs).
+-spec(precondition_failed/2 :: (string(), [any()]) -> no_return()).
+-endif.
 precondition_failed(Format, Params) ->
     rabbit_misc:protocol_error(precondition_failed, Format, Params).
 
diff --git a/src/rabbit_connection_sup.erl b/src/rabbit_connection_sup.erl
index 12a532b6..d9a4735c 100644
--- a/src/rabbit_connection_sup.erl
+++ b/src/rabbit_connection_sup.erl
@@ -42,16 +42,11 @@ start_link() ->
           SupPid,
           {collector, {rabbit_queue_collector, start_link, []},
            intrinsic, ?MAX_WAIT, worker, [rabbit_queue_collector]}),
-    {ok, ChannelSupSupPid} =
-        supervisor2:start_child(
-          SupPid,
-          {channel_sup_sup, {rabbit_channel_sup_sup, start_link, []},
-           intrinsic, infinity, supervisor, [rabbit_channel_sup_sup]}),
     {ok, ReaderPid} =
         supervisor2:start_child(
           SupPid,
           {reader, {rabbit_reader, start_link,
-                    [ChannelSupSupPid, Collector,
+                    [SupPid, Collector,
                      rabbit_heartbeat:start_heartbeat_fun(SupPid)]},
            intrinsic, ?MAX_WAIT, worker, [rabbit_reader]}),
     {ok, SupPid, ReaderPid}.
diff --git a/src/rabbit_exchange_type_invalid.erl b/src/rabbit_exchange_type_invalid.erl
index 101fe434..c5d781c2 100644
--- a/src/rabbit_exchange_type_invalid.erl
+++ b/src/rabbit_exchange_type_invalid.erl
@@ -31,6 +31,10 @@ description() ->
 
 serialise_events() -> false.
 
+-ifdef(use_specs).
+-spec(route/2 :: (rabbit_types:exchange(), rabbit_types:delivery())
+                 -> no_return()).
+-endif.
 route(#exchange{name = Name, type = Type}, _) ->
     rabbit_misc:protocol_error(
       precondition_failed,
diff --git a/src/rabbit_mirror_queue_master.erl b/src/rabbit_mirror_queue_master.erl
index b5f72cad..c704804e 100644
--- a/src/rabbit_mirror_queue_master.erl
+++ b/src/rabbit_mirror_queue_master.erl
@@ -17,7 +17,7 @@
 -module(rabbit_mirror_queue_master).
 
 -export([init/3, terminate/2, delete_and_terminate/2,
-         purge/1, publish/5, publish_delivered/4,
+         purge/1, purge_acks/1, publish/5, publish_delivered/4,
          discard/3, fetch/2, drop/2, ack/2, requeue/2, ackfold/4, fold/3,
          len/1, is_empty/1, depth/1, drain_confirmed/1,
          dropwhile/2, fetchwhile/4, set_ram_duration_target/2, ram_duration/1,
@@ -198,6 +198,8 @@ purge(State = #state { gm                  = GM,
     {Count, BQS1} = BQ:purge(BQS),
     {Count, State #state { backing_queue_state = BQS1 }}.
 
+purge_acks(_State) -> exit({not_implemented, {?MODULE, purge_acks}}).
+
 publish(Msg = #basic_message { id = MsgId }, MsgProps, IsDelivered, ChPid,
         State = #state { gm                  = GM,
                          seen_status         = SS,
diff --git a/src/rabbit_mirror_queue_slave.erl b/src/rabbit_mirror_queue_slave.erl
index 9f12b34e..27b0326d 100644
--- a/src/rabbit_mirror_queue_slave.erl
+++ b/src/rabbit_mirror_queue_slave.erl
@@ -37,18 +37,10 @@
 
 -include("rabbit.hrl").
 
-%%----------------------------------------------------------------------------
-
 -include("gm_specs.hrl").
 
--ifdef(use_specs).
-%% Shut dialyzer up
--spec(promote_me/2 :: (_, _) -> no_return()).
--endif.
-
 %%----------------------------------------------------------------------------
 
-
 -define(CREATION_EVENT_KEYS,
         [pid,
          name,
@@ -79,6 +71,8 @@
                  depth_delta
                }).
 
+%%----------------------------------------------------------------------------
+
 start_link(Q) -> gen_server2:start_link(?MODULE, Q, []).
 
 set_maximum_since_use(QPid, Age) ->
@@ -227,10 +221,12 @@ handle_cast({sync_start, Ref, Syncer},
                              backing_queue       = BQ,
                              backing_queue_state = BQS }) ->
     State1 = #state{rate_timer_ref = TRef} = ensure_rate_timer(State),
-    S = fun({TRefN, BQSN}) -> State1#state{depth_delta         = undefined,
-                                           rate_timer_ref      = TRefN,
-                                           backing_queue_state = BQSN} end,
-    %% [0] We can only sync when there are no pending acks
+    S = fun({MA, TRefN, BQSN}) ->
+                State1#state{depth_delta         = undefined,
+                             msg_id_ack          = dict:from_list(MA),
+                             rate_timer_ref      = TRefN,
+                             backing_queue_state = BQSN}
+        end,
     case rabbit_mirror_queue_sync:slave(
            DD, Ref, TRef, Syncer, BQ, BQS,
            fun (BQN, BQSN) ->
@@ -240,7 +236,7 @@ handle_cast({sync_start, Ref, Syncer},
                    {TRefN, BQSN1}
            end) of
         denied              -> noreply(State1);
-        {ok,           Res} -> noreply(set_delta(0, S(Res))); %% [0]
+        {ok,           Res} -> noreply(set_delta(0, S(Res)));
         {failed,       Res} -> noreply(S(Res));
         {stop, Reason, Res} -> {stop, Reason, S(Res)}
     end;
@@ -469,6 +465,9 @@ confirm_messages(MsgIds, State = #state { msg_id_status = MS }) ->
 handle_process_result({ok,   State}) -> noreply(State);
 handle_process_result({stop, State}) -> {stop, normal, State}.
 
+-ifdef(use_specs).
+-spec(promote_me/2 :: ({pid(), term()}, #state{}) -> no_return()).
+-endif.
 promote_me(From, #state { q                   = Q = #amqqueue { name = QName },
                           gm                  = GM,
                           backing_queue       = BQ,
diff --git a/src/rabbit_mirror_queue_sync.erl b/src/rabbit_mirror_queue_sync.erl
index f2ab67cd..b8cfe4a9 100644
--- a/src/rabbit_mirror_queue_sync.erl
+++ b/src/rabbit_mirror_queue_sync.erl
@@ -57,6 +57,9 @@
 -type(log_fun() :: fun ((string(), [any()]) -> 'ok')).
 -type(bq() :: atom()).
 -type(bqs() :: any()).
+-type(ack() :: any()).
+-type(slave_sync_state() :: {[{rabbit_types:msg_id(), ack()}], timer:tref(),
+                             bqs()}).
 
 -spec(master_prepare/3 :: (reference(), log_fun(), [pid()]) -> pid()).
 -spec(master_go/7 :: (pid(), reference(), log_fun(),
@@ -69,8 +72,8 @@
 -spec(slave/7 :: (non_neg_integer(), reference(), timer:tref(), pid(),
                   bq(), bqs(), fun((bq(), bqs()) -> {timer:tref(), bqs()})) ->
                       'denied' |
-                      {'ok' | 'failed', {timer:tref(), bqs()}} |
-                      {'stop', any(), {timer:tref(), bqs()}}).
+                      {'ok' | 'failed', slave_sync_state()} |
+                      {'stop', any(), slave_sync_state()}).
 
 -endif.
 
@@ -91,16 +94,16 @@ master_go(Syncer, Ref, Log, HandleInfo, EmitStats, BQ, BQS) ->
     end.
 
 master_go0(Args, BQ, BQS) ->
-    case BQ:fold(fun (Msg, MsgProps, Acc) ->
-                         master_send(Msg, MsgProps, Args, Acc)
+    case BQ:fold(fun (Msg, MsgProps, Unacked, Acc) ->
+                         master_send(Msg, MsgProps, Unacked, Args, Acc)
                  end, {0, erlang:now()}, BQS) of
         {{shutdown,  Reason}, BQS1} -> {shutdown,  Reason, BQS1};
         {{sync_died, Reason}, BQS1} -> {sync_died, Reason, BQS1};
         {_,                   BQS1} -> master_done(Args, BQS1)
     end.
 
-master_send(Msg, MsgProps, {Syncer, Ref, Log, HandleInfo, EmitStats, Parent},
-            {I, Last}) ->
+master_send(Msg, MsgProps, Unacked,
+            {Syncer, Ref, Log, HandleInfo, EmitStats, Parent}, {I, Last}) ->
     T = case timer:now_diff(erlang:now(), Last) > ?SYNC_PROGRESS_INTERVAL of
             true  -> EmitStats({syncing, I}),
                      Log("~p messages", [I]),
@@ -119,7 +122,7 @@ master_send(Msg, MsgProps, {Syncer, Ref, Log, HandleInfo, EmitStats, Parent},
          cancel_sync_mirrors}    -> stop_syncer(Syncer, {cancel, Ref}),
                                     gen_server2:reply(From, ok),
                                     {stop, cancelled};
-        {next, Ref}              -> Syncer ! {msg, Ref, Msg, MsgProps},
+        {next, Ref}              -> Syncer ! {msg, Ref, Msg, MsgProps, Unacked},
                                     {cont, {I + 1, T}};
         {'EXIT', Parent, Reason} -> {stop, {shutdown,  Reason}};
         {'EXIT', Syncer, Reason} -> {stop, {sync_died, Reason}}
@@ -164,11 +167,11 @@ syncer(Ref, Log, MPid, SPids) ->
 syncer_loop(Ref, MPid, SPids) ->
     MPid ! {next, Ref},
     receive
-        {msg, Ref, Msg, MsgProps} ->
+        {msg, Ref, Msg, MsgProps, Unacked} ->
             SPids1 = wait_for_credit(SPids),
             [begin
                  credit_flow:send(SPid),
-                 SPid ! {sync_msg, Ref, Msg, MsgProps}
+                 SPid ! {sync_msg, Ref, Msg, MsgProps, Unacked}
              end || SPid <- SPids1],
             syncer_loop(Ref, MPid, SPids1);
         {cancel, Ref} ->
@@ -204,12 +207,12 @@ slave(0, Ref, _TRef, Syncer, _BQ, _BQS, _UpdateRamDuration) ->
 slave(_DD, Ref, TRef, Syncer, BQ, BQS, UpdateRamDuration) ->
     MRef = erlang:monitor(process, Syncer),
     Syncer ! {sync_ready, Ref, self()},
-    {_MsgCount, BQS1} = BQ:purge(BQS),
+    {_MsgCount, BQS1} = BQ:purge(BQ:purge_acks(BQS)),
     slave_sync_loop({Ref, MRef, Syncer, BQ, UpdateRamDuration,
-                     rabbit_misc:get_parent()}, TRef, BQS1).
+                     rabbit_misc:get_parent()}, {[], TRef, BQS1}).
 
 slave_sync_loop(Args = {Ref, MRef, Syncer, BQ, UpdateRamDuration, Parent},
-                TRef, BQS) ->
+                State = {MA, TRef, BQS}) ->
     receive
         {'DOWN', MRef, process, Syncer, _Reason} ->
             %% If the master dies half way we are not in the usual
@@ -218,34 +221,40 @@ slave_sync_loop(Args = {Ref, MRef, Syncer, BQ, UpdateRamDuration, Parent},
             %% sync with a newly promoted master, or even just receive
             %% messages from it, we have a hole in the middle. So the
             %% only thing to do here is purge.
-            {_MsgCount, BQS1} = BQ:purge(BQS),
+            {_MsgCount, BQS1} = BQ:purge(BQ:purge_acks(BQS)),
             credit_flow:peer_down(Syncer),
-            {failed, {TRef, BQS1}};
+            {failed, {[], TRef, BQS1}};
         {bump_credit, Msg} ->
             credit_flow:handle_bump_msg(Msg),
-            slave_sync_loop(Args, TRef, BQS);
+            slave_sync_loop(Args, State);
         {sync_complete, Ref} ->
             erlang:demonitor(MRef, [flush]),
             credit_flow:peer_down(Syncer),
-            {ok, {TRef, BQS}};
+            {ok, State};
         {'$gen_cast', {set_maximum_since_use, Age}} ->
             ok = file_handle_cache:set_maximum_since_use(Age),
-            slave_sync_loop(Args, TRef, BQS);
+            slave_sync_loop(Args, State);
         {'$gen_cast', {set_ram_duration_target, Duration}} ->
             BQS1 = BQ:set_ram_duration_target(Duration, BQS),
-            slave_sync_loop(Args, TRef, BQS1);
+            slave_sync_loop(Args, {MA, TRef, BQS1});
         update_ram_duration ->
             {TRef1, BQS1} = UpdateRamDuration(BQ, BQS),
-            slave_sync_loop(Args, TRef1, BQS1);
-        {sync_msg, Ref, Msg, Props} ->
+            slave_sync_loop(Args, {MA, TRef1, BQS1});
+        {sync_msg, Ref, Msg, Props, Unacked} ->
             credit_flow:ack(Syncer),
             Props1 = Props#message_properties{needs_confirming = false},
-            BQS1 = BQ:publish(Msg, Props1, true, none, BQS),
-            slave_sync_loop(Args, TRef, BQS1);
+            {MA1, BQS1} =
+                case Unacked of
+                    false -> {MA, BQ:publish(Msg, Props1, true, none, BQS)};
+                    true  -> {AckTag, BQS2} = BQ:publish_delivered(
+                                                Msg, Props1, none, BQS),
+                             {[{Msg#basic_message.id, AckTag} | MA], BQS2}
+                end,
+            slave_sync_loop(Args, {MA1, TRef, BQS1});
         {'EXIT', Parent, Reason} ->
-            {stop, Reason, {TRef, BQS}};
+            {stop, Reason, State};
         %% If the master throws an exception
         {'$gen_cast', {gm, {delete_and_terminate, Reason}}} ->
             BQ:delete_and_terminate(Reason, BQS),
-            {stop, Reason, {TRef, undefined}}
+            {stop, Reason, {[], TRef, undefined}}
     end.
diff --git a/src/rabbit_networking.erl b/src/rabbit_networking.erl
index 31eeef73..080e0987 100644
--- a/src/rabbit_networking.erl
+++ b/src/rabbit_networking.erl
@@ -18,7 +18,8 @@
 
 -export([boot/0, start/0, start_tcp_listener/1, start_ssl_listener/2,
          stop_tcp_listener/1, on_node_down/1, active_listeners/0,
-         node_listeners/1, connections/0, connection_info_keys/0,
+         node_listeners/1, register_connection/1, unregister_connection/1,
+         connections/0, connection_info_keys/0,
          connection_info/1, connection_info/2,
          connection_info_all/0, connection_info_all/1,
          close_connection/2, force_connection_event_refresh/0, tcp_host/1]).
@@ -65,6 +66,8 @@
 -spec(stop_tcp_listener/1 :: (listener_config()) -> 'ok').
 -spec(active_listeners/0 :: () -> [rabbit_types:listener()]).
 -spec(node_listeners/1 :: (node()) -> [rabbit_types:listener()]).
+-spec(register_connection/1 :: (pid()) -> ok).
+-spec(unregister_connection/1 :: (pid()) -> ok).
 -spec(connections/0 :: () -> [rabbit_types:connection()]).
 -spec(connections_local/0 :: () -> [rabbit_types:connection()]).
 -spec(connection_info_keys/0 :: () -> rabbit_types:info_keys()).
@@ -294,20 +297,15 @@ start_client(Sock) ->
 start_ssl_client(SslOpts, Sock) ->
     start_client(Sock, ssl_transform_fun(SslOpts)).
 
+register_connection(Pid) -> pg_local:join(rabbit_connections, Pid).
+
+unregister_connection(Pid) -> pg_local:leave(rabbit_connections, Pid).
+
 connections() ->
     rabbit_misc:append_rpc_all_nodes(rabbit_mnesia:cluster_nodes(running),
                                      rabbit_networking, connections_local, []).
 
-connections_local() ->
-    [Reader ||
-        {_, ConnSup, supervisor, _}
-            <- supervisor:which_children(rabbit_tcp_client_sup),
-        Reader <- [try
-                       rabbit_connection_sup:reader(ConnSup)
-                   catch exit:{noproc, _} ->
-                           noproc
-                   end],
-        Reader =/= noproc].
+connections_local() -> pg_local:get_members(rabbit_connections).
 
 connection_info_keys() -> rabbit_reader:info_keys().
 
diff --git a/src/rabbit_reader.erl b/src/rabbit_reader.erl
index 7a28c8a3..ae832749 100644
--- a/src/rabbit_reader.erl
+++ b/src/rabbit_reader.erl
@@ -23,7 +23,7 @@
 
 -export([system_continue/3, system_terminate/4, system_code_change/4]).
 
--export([init/4, mainloop/2]).
+-export([init/4, mainloop/2, recvloop/2]).
 
 -export([conserve_resources/3, server_properties/1]).
 
@@ -37,7 +37,8 @@
 
 -record(v1, {parent, sock, connection, callback, recv_len, pending_recv,
              connection_state, queue_collector, heartbeater, stats_timer,
-             channel_sup_sup_pid, start_heartbeat_fun, buf, buf_len, throttle}).
+             conn_sup_pid, channel_sup_sup_pid, start_heartbeat_fun,
+             buf, buf_len, throttle}).
 
 -record(connection, {name, host, peer_host, port, peer_port,
                      protocol, user, timeout_sec, frame_max, vhost,
@@ -109,12 +110,12 @@ start_link(ChannelSupSupPid, Collector, StartHeartbeatFun) ->
 shutdown(Pid, Explanation) ->
     gen_server:call(Pid, {shutdown, Explanation}, infinity).
 
-init(Parent, ChannelSupSupPid, Collector, StartHeartbeatFun) ->
+init(Parent, ConnSupPid, Collector, StartHeartbeatFun) ->
     Deb = sys:debug_options([]),
     receive
         {go, Sock, SockTransform} ->
             start_connection(
-              Parent, ChannelSupSupPid, Collector, StartHeartbeatFun, Deb, Sock,
+              Parent, ConnSupPid, Collector, StartHeartbeatFun, Deb, Sock,
               SockTransform)
     end.
 
@@ -203,7 +204,7 @@ name(Sock) ->
 socket_ends(Sock) ->
     socket_op(Sock, fun (S) -> rabbit_net:socket_ends(S, inbound) end).
 
-start_connection(Parent, ChannelSupSupPid, Collector, StartHeartbeatFun, Deb,
+start_connection(Parent, ConnSupPid, Collector, StartHeartbeatFun, Deb,
                  Sock, SockTransform) ->
     process_flag(trap_exit, true),
     Name = name(Sock),
@@ -234,7 +235,8 @@ start_connection(Parent, ChannelSupSupPid, Collector, StartHeartbeatFun, Deb,
                 connection_state    = pre_init,
                 queue_collector     = Collector,
                 heartbeater         = none,
-                channel_sup_sup_pid = ChannelSupSupPid,
+                conn_sup_pid        = ConnSupPid,
+                channel_sup_sup_pid = none,
                 start_heartbeat_fun = StartHeartbeatFun,
                 buf                 = [],
                 buf_len             = 0,
@@ -244,9 +246,10 @@ start_connection(Parent, ChannelSupSupPid, Collector, StartHeartbeatFun, Deb,
                   last_blocked_at    = never}},
     try
         ok = inet_op(fun () -> rabbit_net:tune_buffer_size(ClientSock) end),
-        recvloop(Deb, switch_callback(rabbit_event:init_stats_timer(
-                                       State, #v1.stats_timer),
-                                      handshake, 8)),
+        run({?MODULE, recvloop,
+             [Deb, switch_callback(rabbit_event:init_stats_timer(
+                                     State, #v1.stats_timer),
+                                   handshake, 8)]}),
         log(info, "closing AMQP connection ~p (~s)~n", [self(), Name])
     catch
         Ex -> log(case Ex of
@@ -263,10 +266,16 @@ start_connection(Parent, ChannelSupSupPid, Collector, StartHeartbeatFun, Deb,
         %% accounting as accurate as possible we ought to close the
         %% socket w/o delay before termination.
         rabbit_net:fast_close(ClientSock),
+        rabbit_networking:unregister_connection(self()),
         rabbit_event:notify(connection_closed, [{pid, self()}])
     end,
     done.
 
+run({M, F, A}) ->
+    try apply(M, F, A)
+    catch {become, MFA} -> run(MFA)
+    end.
+
 recvloop(Deb, State = #v1{pending_recv = true}) ->
     mainloop(Deb, State);
 recvloop(Deb, State = #v1{connection_state = blocked}) ->
@@ -689,8 +698,17 @@ handle_input(handshake, <<"AMQP", 1, 1, 8, 0>>, State) ->
 handle_input(handshake, <<"AMQP", 1, 1, 9, 1>>, State) ->
     start_connection({8, 0, 0}, rabbit_framing_amqp_0_8, State);
 
+%% ... and finally, the 1.0 spec is crystal clear!  Note that the
+%% TLS uses a different protocol number, and would go here.
+handle_input(handshake, <<"AMQP", 0, 1, 0, 0>>, State) ->
+    become_1_0(amqp, {0, 1, 0, 0}, State);
+
+%% 3 stands for "SASL"
+handle_input(handshake, <<"AMQP", 3, 1, 0, 0>>, State) ->
+    become_1_0(sasl, {3, 1, 0, 0}, State);
+
 handle_input(handshake, <<"AMQP", A, B, C, D>>, #v1{sock = Sock}) ->
-    refuse_connection(Sock, {bad_version, A, B, C, D});
+    refuse_connection(Sock, {bad_version, {A, B, C, D}});
 
 handle_input(handshake, Other, #v1{sock = Sock}) ->
     refuse_connection(Sock, {bad_header, Other});
@@ -704,6 +722,7 @@ handle_input(Callback, Data, _State) ->
 start_connection({ProtocolMajor, ProtocolMinor, _ProtocolRevision},
                  Protocol,
                  State = #v1{sock = Sock, connection = Connection}) ->
+    rabbit_networking:register_connection(self()),
     Start = #'connection.start'{
       version_major = ProtocolMajor,
       version_minor = ProtocolMinor,
@@ -799,17 +818,24 @@ handle_method0(#'connection.open'{virtual_host = VHostPath},
                            connection       = Connection = #connection{
                                                 user = User,
                                                 protocol = Protocol},
+                           conn_sup_pid     = ConnSupPid,
                            sock             = Sock,
                            throttle         = Throttle}) ->
     ok = rabbit_access_control:check_vhost_access(User, VHostPath),
     NewConnection = Connection#connection{vhost = VHostPath},
     ok = send_on_channel0(Sock, #'connection.open_ok'{}, Protocol),
     Conserve = rabbit_alarm:register(self(), {?MODULE, conserve_resources, []}),
+    Throttle1 = Throttle#throttle{conserve_resources = Conserve},
+    {ok, ChannelSupSupPid} =
+        supervisor2:start_child(
+          ConnSupPid,
+          {channel_sup_sup, {rabbit_channel_sup_sup, start_link, []},
+           intrinsic, infinity, supervisor, [rabbit_channel_sup_sup]}),
     State1 = control_throttle(
-               State#v1{connection_state   = running,
-                        connection         = NewConnection,
-                        throttle           = Throttle#throttle{
-                                               conserve_resources = Conserve}}),
+               State#v1{connection_state    = running,
+                        connection          = NewConnection,
+                        channel_sup_sup_pid = ChannelSupSupPid,
+                        throttle            = Throttle1}),
     rabbit_event:notify(connection_created,
                         [{type, network} |
                          infos(?CREATION_EVENT_KEYS, State1)]),
@@ -979,3 +1005,29 @@ cert_info(F, #v1{sock = Sock}) ->
 emit_stats(State) ->
     rabbit_event:notify(connection_stats, infos(?STATISTICS_KEYS, State)),
     rabbit_event:reset_stats_timer(State, #v1.stats_timer).
+
+%% 1.0 stub
+-ifdef(use_specs).
+-spec(become_1_0/3 :: ('amqp' | 'sasl',
+                       {non_neg_integer(), non_neg_integer(),
+                        non_neg_integer(), non_neg_integer()},
+                       #v1{}) -> no_return()).
+-endif.
+become_1_0(Mode, Version, State = #v1{sock = Sock}) ->
+    case code:is_loaded(rabbit_amqp1_0_reader) of
+        false -> refuse_connection(Sock, {bad_version, Version});
+        _     -> throw({become, {rabbit_amqp1_0_reader, become,
+                                 [Mode, pack_for_1_0(State)]}})
+    end.
+
+pack_for_1_0(#v1{parent              = Parent,
+                 sock                = Sock,
+                 recv_len            = RecvLen,
+                 pending_recv        = PendingRecv,
+                 queue_collector     = QueueCollector,
+                 conn_sup_pid        = ConnSupPid,
+                 start_heartbeat_fun = SHF,
+                 buf                 = Buf,
+                 buf_len             = BufLen}) ->
+    {Parent, Sock, RecvLen, PendingRecv, QueueCollector, ConnSupPid, SHF,
+     Buf, BufLen}.
diff --git a/src/rabbit_tests.erl b/src/rabbit_tests.erl
index 7257827a..b0ff5af9 100644
--- a/src/rabbit_tests.erl
+++ b/src/rabbit_tests.erl
@@ -1086,7 +1086,7 @@ test_policy_validation() ->
 
 test_server_status() ->
     %% create a few things so there is some useful information to list
-    Writer = spawn(fun () -> receive shutdown -> ok end end),
+    Writer = spawn(fun test_writer/0),
     {ok, Ch} = rabbit_channel:start_link(
                  1, self(), Writer, self(), "", rabbit_framing_amqp_0_9_1,
                  user(<<"user">>), <<"/">>, [], self(),
@@ -1123,7 +1123,8 @@ test_server_status() ->
         [L || L = #listener{node = N} <- rabbit_networking:active_listeners(),
               N =:= node()],
 
-    {ok, _C} = gen_tcp:connect(H, P, []),
+    {ok, C} = gen_tcp:connect(H, P, []),
+    gen_tcp:send(C, <<"AMQP", 0, 0, 9, 1>>),
     timer:sleep(100),
     ok = info_action(list_connections,
                      rabbit_networking:connection_info_keys(), false),
@@ -1160,10 +1161,15 @@ test_server_status() ->
 
     passed.
 
+test_writer() -> test_writer(none).
+
 test_writer(Pid) ->
     receive
-        shutdown               -> ok;
-        {send_command, Method} -> Pid ! Method, test_writer(Pid)
+        {'$gen_call', From, flush} -> gen_server:reply(From, ok),
+                                      test_writer(Pid);
+        {send_command, Method}     -> Pid ! Method,
+                                      test_writer(Pid);
+        shutdown                   -> ok
     end.
 
 test_spawn() ->
@@ -2322,21 +2328,26 @@ test_variable_queue() ->
               fun test_dropwhile_varying_ram_duration/1,
               fun test_fetchwhile_varying_ram_duration/1,
               fun test_variable_queue_ack_limiting/1,
+              fun test_variable_queue_purge/1,
               fun test_variable_queue_requeue/1,
               fun test_variable_queue_fold/1]],
     passed.
 
 test_variable_queue_fold(VQ0) ->
-    {Count, RequeuedMsgs, FreshMsgs, VQ1} = variable_queue_with_holes(VQ0),
-    Msgs = RequeuedMsgs ++ FreshMsgs,
-    lists:foldl(
-      fun (Cut, VQ2) -> test_variable_queue_fold(Cut, Msgs, VQ2) end,
-      VQ1, [0, 1, 2, Count div 2, Count - 1, Count, Count + 1, Count * 2]).
-
-test_variable_queue_fold(Cut, Msgs, VQ0) ->
+    {PendingMsgs, RequeuedMsgs, FreshMsgs, VQ1} =
+        variable_queue_with_holes(VQ0),
+    Count = rabbit_variable_queue:depth(VQ1),
+    Msgs = lists:sort(PendingMsgs ++ RequeuedMsgs ++ FreshMsgs),
+    lists:foldl(fun (Cut, VQ2) ->
+                        test_variable_queue_fold(Cut, Msgs, PendingMsgs, VQ2)
+                end, VQ1, [0, 1, 2, Count div 2,
+                           Count - 1, Count, Count + 1, Count * 2]).
+
+test_variable_queue_fold(Cut, Msgs, PendingMsgs, VQ0) ->
     {Acc, VQ1} = rabbit_variable_queue:fold(
-                   fun (M, _, A) ->
+                   fun (M, _, Pending, A) ->
                            MInt = msg2int(M),
+                           Pending = lists:member(MInt, PendingMsgs), %% assert
                            case MInt =< Cut of
                                true  -> {cont, [MInt | A]};
                                false -> {stop, A}
@@ -2397,10 +2408,11 @@ variable_queue_with_holes(VQ0) ->
     Depth = rabbit_variable_queue:depth(VQ8),
     Len = Depth - length(Subset3),
     Len = rabbit_variable_queue:len(VQ8),
-    {Len, (Seq -- Seq3), lists:seq(Count + 1, Count + 64), VQ8}.
+    {Seq3, Seq -- Seq3, lists:seq(Count + 1, Count + 64), VQ8}.
 
 test_variable_queue_requeue(VQ0) ->
-    {_, RequeuedMsgs, FreshMsgs, VQ1} = variable_queue_with_holes(VQ0),
+    {_PendingMsgs, RequeuedMsgs, FreshMsgs, VQ1} =
+        variable_queue_with_holes(VQ0),
     Msgs =
         lists:zip(RequeuedMsgs,
                   lists:duplicate(length(RequeuedMsgs), true)) ++
@@ -2416,6 +2428,21 @@ test_variable_queue_requeue(VQ0) ->
     {empty, VQ3} = rabbit_variable_queue:fetch(true, VQ2),
     VQ3.
 
+test_variable_queue_purge(VQ0) ->
+    LenDepth = fun (VQ) ->
+                       {rabbit_variable_queue:len(VQ),
+                        rabbit_variable_queue:depth(VQ)}
+               end,
+    VQ1         = variable_queue_publish(false, 10, VQ0),
+    {VQ2, Acks} = variable_queue_fetch(6, false, false, 10, VQ1),
+    {4, VQ3}    = rabbit_variable_queue:purge(VQ2),
+    {0, 6}      = LenDepth(VQ3),
+    {_, VQ4}    = rabbit_variable_queue:requeue(lists:sublist(Acks, 2), VQ3),
+    {2, 6}      = LenDepth(VQ4),
+    VQ5         = rabbit_variable_queue:purge_acks(VQ4),
+    {2, 2}      = LenDepth(VQ5),
+    VQ5.
+
 test_variable_queue_ack_limiting(VQ0) ->
     %% start by sending in a bunch of messages
     Len = 1024,
diff --git a/src/rabbit_variable_queue.erl b/src/rabbit_variable_queue.erl
index 8a7045ea..34a4b52f 100644
--- a/src/rabbit_variable_queue.erl
+++ b/src/rabbit_variable_queue.erl
@@ -16,7 +16,7 @@
 
 -module(rabbit_variable_queue).
 
--export([init/3, terminate/2, delete_and_terminate/2, purge/1,
+-export([init/3, terminate/2, delete_and_terminate/2, purge/1, purge_acks/1,
          publish/5, publish_delivered/4, discard/3, drain_confirmed/1,
          dropwhile/2, fetchwhile/4,
          fetch/2, drop/2, ack/2, requeue/2, ackfold/4, fold/3, len/1,
@@ -519,6 +519,8 @@ purge(State = #vqstate { q4                = Q4,
                               ram_msg_count     = 0,
                               persistent_count  = PCount1 })}.
 
+purge_acks(State) -> a(purge_pending_ack(false, State)).
+
 publish(Msg = #basic_message { is_persistent = IsPersistent, id = MsgId },
         MsgProps = #message_properties { needs_confirming = NeedsConfirming },
         IsDelivered, _ChPid, State = #vqstate { q1 = Q1, q3 = Q3, q4 = Q4,
@@ -676,25 +678,12 @@ ackfold(MsgFun, Acc, State, AckTags) ->
                     end, {Acc, State}, AckTags),
     {AccN, a(StateN)}.
 
-fold(Fun, Acc, #vqstate { q1    = Q1,
-                          q2    = Q2,
-                          delta = #delta { start_seq_id = DeltaSeqId,
-                                           end_seq_id   = DeltaSeqIdEnd },
-                          q3    = Q3,
-                          q4    = Q4 } = State) ->
-    QFun = fun(MsgStatus, {Acc0, State0}) ->
-                   {Msg, State1} = read_msg(MsgStatus, State0),
-                   {StopGo, AccNext} =
-                       Fun(Msg, MsgStatus#msg_status.msg_props, Acc0),
-                   {StopGo, {AccNext, State1}}
-           end,
-    {Cont1, {Acc1, State1}} = qfoldl(QFun, {cont,  {Acc,  State }}, Q4),
-    {Cont2, {Acc2, State2}} = qfoldl(QFun, {Cont1, {Acc1, State1}}, Q3),
-    {Cont3, {Acc3, State3}} = delta_fold(Fun, {Cont2, Acc2},
-                                         DeltaSeqId, DeltaSeqIdEnd, State2),
-    {Cont4, {Acc4, State4}} = qfoldl(QFun, {Cont3, {Acc3, State3}}, Q2),
-    {_,     {Acc5, State5}} = qfoldl(QFun, {Cont4, {Acc4, State4}}, Q1),
-    {Acc5, State5}.
+fold(Fun, Acc, State = #vqstate{index_state = IndexState}) ->
+    {Its, IndexState1} = lists:foldl(fun inext/2, {[], IndexState},
+                                     [msg_iterator(State),
+                                      disk_ack_iterator(State),
+                                      ram_ack_iterator(State)]),
+    ifold(Fun, Acc, Its, State#vqstate{index_state = IndexState1}).
 
 len(#vqstate { len = Len }) -> Len.
 
@@ -1101,14 +1090,16 @@ queue_out(State = #vqstate { q4 = Q4 }) ->
 
 read_msg(#msg_status{msg           = undefined,
                      msg_id        = MsgId,
-                     is_persistent = IsPersistent},
-         State = #vqstate{msg_store_clients = MSCState}) ->
-    {{ok, Msg = #basic_message {}}, MSCState1} =
-        msg_store_read(MSCState, IsPersistent, MsgId),
-    {Msg, State #vqstate {msg_store_clients = MSCState1}};
+                     is_persistent = IsPersistent}, State) ->
+    read_msg(MsgId, IsPersistent, State);
 read_msg(#msg_status{msg = Msg}, State) ->
     {Msg, State}.
 
+read_msg(MsgId, IsPersistent, State = #vqstate{msg_store_clients = MSCState}) ->
+    {{ok, Msg = #basic_message {}}, MSCState1} =
+        msg_store_read(MSCState, IsPersistent, MsgId),
+    {Msg, State #vqstate {msg_store_clients = MSCState1}}.
+
 inc_ram_msg_count(State = #vqstate{ram_msg_count = RamMsgCount}) ->
     State#vqstate{ram_msg_count = RamMsgCount + 1}.
 
@@ -1389,7 +1380,7 @@ msg_indices_written_to_disk(Callback, MsgIdSet) ->
              end).
 
 %%----------------------------------------------------------------------------
-%% Internal plumbing for requeue and fold
+%% Internal plumbing for requeue
 %%----------------------------------------------------------------------------
 
 publish_alpha(#msg_status { msg = undefined } = MsgStatus, State) ->
@@ -1459,48 +1450,81 @@ beta_limit(Q) ->
 delta_limit(?BLANK_DELTA_PATTERN(_X))             -> undefined;
 delta_limit(#delta { start_seq_id = StartSeqId }) -> StartSeqId.
 
-qfoldl(_Fun, {stop, _Acc} = A, _Q) -> A;
-qfoldl( Fun, {cont,  Acc} = A,  Q) ->
+%%----------------------------------------------------------------------------
+%% Iterator
+%%----------------------------------------------------------------------------
+
+ram_ack_iterator(State) ->
+    {ack, gb_trees:iterator(State#vqstate.ram_pending_ack)}.
+
+disk_ack_iterator(State) ->
+    {ack, gb_trees:iterator(State#vqstate.disk_pending_ack)}.
+
+msg_iterator(State) -> istate(start, State).
+
+istate(start, State) -> {q4,    State#vqstate.q4,    State};
+istate(q4,    State) -> {q3,    State#vqstate.q3,    State};
+istate(q3,    State) -> {delta, State#vqstate.delta, State};
+istate(delta, State) -> {q2,    State#vqstate.q2,    State};
+istate(q2,    State) -> {q1,    State#vqstate.q1,    State};
+istate(q1,   _State) -> done.
+
+next({ack, It}, IndexState) ->
+    case gb_trees:next(It) of
+        none                     -> {empty, IndexState};
+        {_SeqId, MsgStatus, It1} -> Next = {ack, It1},
+                                    {value, MsgStatus, true, Next, IndexState}
+    end;
+next(done, IndexState) -> {empty, IndexState};
+next({delta, #delta{start_seq_id = SeqId,
+                    end_seq_id   = SeqId}, State}, IndexState) ->
+    next(istate(delta, State), IndexState);
+next({delta, #delta{start_seq_id = SeqId,
+                    end_seq_id   = SeqIdEnd} = Delta, State}, IndexState) ->
+    SeqIdB = rabbit_queue_index:next_segment_boundary(SeqId),
+    SeqId1 = lists:min([SeqIdB, SeqIdEnd]),
+    {List, IndexState1} = rabbit_queue_index:read(SeqId, SeqId1, IndexState),
+    next({delta, Delta#delta{start_seq_id = SeqId1}, List, State}, IndexState1);
+next({delta, Delta, [], State}, IndexState) ->
+    next({delta, Delta, State}, IndexState);
+next({delta, Delta, [{_, SeqId, _, _, _} = M | Rest], State}, IndexState) ->
+    case (gb_trees:is_defined(SeqId, State#vqstate.ram_pending_ack) orelse
+          gb_trees:is_defined(SeqId, State#vqstate.disk_pending_ack)) of
+        false -> Next = {delta, Delta, Rest, State},
+                 {value, beta_msg_status(M), false, Next, IndexState};
+        true  -> next({delta, Delta, Rest, State}, IndexState)
+    end;
+next({Key, Q, State}, IndexState) ->
     case ?QUEUE:out(Q) of
-        {empty, _Q}      -> A;
-        {{value, V}, Q1} -> qfoldl(Fun, Fun(V, Acc), Q1)
+        {empty, _Q}              -> next(istate(Key, State), IndexState);
+        {{value, MsgStatus}, QN} -> Next = {Key, QN, State},
+                                    {value, MsgStatus, false, Next, IndexState}
     end.
 
-lfoldl(_Fun, {stop, _Acc} = A,      _L) -> A;
-lfoldl(_Fun, {cont, _Acc} = A,      []) -> A;
-lfoldl( Fun, {cont,  Acc},     [H | T]) -> lfoldl(Fun, Fun(H, Acc), T).
-
-delta_fold(_Fun, {stop, Acc},   _DeltaSeqId, _DeltaSeqIdEnd, State) ->
-    {stop, {Acc, State}};
-delta_fold(_Fun, {cont, Acc}, DeltaSeqIdEnd,  DeltaSeqIdEnd, State) ->
-    {cont, {Acc, State}};
-delta_fold( Fun, {cont, Acc},    DeltaSeqId,  DeltaSeqIdEnd,
-           #vqstate { ram_pending_ack   = RPA,
-                      disk_pending_ack  = DPA,
-                      index_state       = IndexState,
-                      msg_store_clients = MSCState } = State) ->
-    DeltaSeqId1 = lists:min(
-                    [rabbit_queue_index:next_segment_boundary(DeltaSeqId),
-                     DeltaSeqIdEnd]),
-    {List, IndexState1} = rabbit_queue_index:read(DeltaSeqId, DeltaSeqId1,
-                                                  IndexState),
-    {StopCont, {Acc1, MSCState1}} =
-        lfoldl(fun ({MsgId, SeqId, MsgProps, IsPersistent, _IsDelivered},
-                    {Acc0, MSCState0}) ->
-                       case (gb_trees:is_defined(SeqId, RPA) orelse
-                             gb_trees:is_defined(SeqId, DPA)) of
-                           false -> {{ok, Msg = #basic_message{}}, MSCState1} =
-                                        msg_store_read(MSCState0, IsPersistent,
-                                                       MsgId),
-                                    {StopCont, AccNext} =
-                                        Fun(Msg, MsgProps, Acc0),
-                                    {StopCont, {AccNext, MSCState1}};
-                           true  -> {cont, {Acc0, MSCState0}}
-                       end
-               end, {cont, {Acc, MSCState}}, List),
-    delta_fold(Fun, {StopCont, Acc1}, DeltaSeqId1, DeltaSeqIdEnd,
-               State #vqstate { index_state       = IndexState1,
-                                msg_store_clients = MSCState1 }).
+inext(It, {Its, IndexState}) ->
+    case next(It, IndexState) of
+        {empty, IndexState1} ->
+            {Its, IndexState1};
+        {value, MsgStatus1, Unacked, It1, IndexState1} ->
+            {[{MsgStatus1, Unacked, It1} | Its], IndexState1}
+    end.
+
+ifold(_Fun, Acc, [], State) ->
+    {Acc, State};
+ifold(Fun, Acc, Its, State) ->
+    [{MsgStatus, Unacked, It} | Rest] =
+        lists:sort(fun ({#msg_status{seq_id = SeqId1}, _, _},
+                        {#msg_status{seq_id = SeqId2}, _, _}) ->
+                           SeqId1 =< SeqId2
+                   end, Its),
+    {Msg, State1} = read_msg(MsgStatus, State),
+    case Fun(Msg, MsgStatus#msg_status.msg_props, Unacked, Acc) of
+        {stop, Acc1} ->
+            {Acc1, State};
+        {cont, Acc1} ->
+            {Its1, IndexState1} = inext(It, {Rest, State1#vqstate.index_state}),
+            ifold(Fun, Acc1, Its1, State1#vqstate{index_state = IndexState1})
+    end.
 
 %%----------------------------------------------------------------------------
 %% Phase changes
diff --git a/src/rabbit_writer.erl b/src/rabbit_writer.erl
index a7ea3d99..059d3839 100644
--- a/src/rabbit_writer.erl
+++ b/src/rabbit_writer.erl
@@ -21,7 +21,8 @@
 -export([start/5, start_link/5, start/6, start_link/6]).
 -export([send_command/2, send_command/3,
          send_command_sync/2, send_command_sync/3,
-         send_command_and_notify/4, send_command_and_notify/5]).
+         send_command_and_notify/4, send_command_and_notify/5,
+         flush/1]).
 -export([internal_send_command/4, internal_send_command/6]).
 
 %% internal
@@ -69,6 +70,7 @@
         (pid(), pid(), pid(), rabbit_framing:amqp_method_record(),
          rabbit_types:content())
         -> 'ok').
+-spec(flush/1 :: (pid()) -> 'ok').
 -spec(internal_send_command/4 ::
         (rabbit_net:socket(), rabbit_channel:channel_number(),
          rabbit_framing:amqp_method_record(), rabbit_types:protocol())
@@ -130,7 +132,7 @@ mainloop1(State) ->
     receive
         Message -> ?MODULE:mainloop1(handle_message(Message, State))
     after 0 ->
-            ?MODULE:mainloop1(flush(State))
+            ?MODULE:mainloop1(internal_flush(State))
     end.
 
 handle_message({send_command, MethodRecord}, State) ->
@@ -138,12 +140,18 @@ handle_message({send_command, MethodRecord}, State) ->
 handle_message({send_command, MethodRecord, Content}, State) ->
     internal_send_command_async(MethodRecord, Content, State);
 handle_message({'$gen_call', From, {send_command_sync, MethodRecord}}, State) ->
-    State1 = flush(internal_send_command_async(MethodRecord, State)),
+    State1 = internal_flush(
+               internal_send_command_async(MethodRecord, State)),
     gen_server:reply(From, ok),
     State1;
 handle_message({'$gen_call', From, {send_command_sync, MethodRecord, Content}},
                State) ->
-    State1 = flush(internal_send_command_async(MethodRecord, Content, State)),
+    State1 = internal_flush(
+               internal_send_command_async(MethodRecord, Content, State)),
+    gen_server:reply(From, ok),
+    State1;
+handle_message({'$gen_call', From, flush}, State) ->
+    State1 = internal_flush(State),
     gen_server:reply(From, ok),
     State1;
 handle_message({send_command_and_notify, QPid, ChPid, MethodRecord}, State) ->
@@ -192,6 +200,8 @@ send_command_and_notify(W, Q, ChPid, MethodRecord, Content) ->
     W ! {send_command_and_notify, Q, ChPid, MethodRecord, Content},
     ok.
 
+flush(W) -> call(W, flush).
+
 %%---------------------------------------------------------------------------
 
 call(Pid, Msg) ->
@@ -251,13 +261,13 @@ internal_send_command_async(MethodRecord, Content,
 
 maybe_flush(State = #wstate{pending = Pending}) ->
     case iolist_size(Pending) >= ?FLUSH_THRESHOLD of
-        true  -> flush(State);
+        true  -> internal_flush(State);
         false -> State
     end.
 
-flush(State = #wstate{pending = []}) ->
+internal_flush(State = #wstate{pending = []}) ->
     State;
-flush(State = #wstate{sock = Sock, pending = Pending}) ->
+internal_flush(State = #wstate{sock = Sock, pending = Pending}) ->
     ok = port_cmd(Sock, lists:reverse(Pending)),
     State#wstate{pending = []}.