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%% This Source Code Form is subject to the terms of the Mozilla Public
%% License, v. 2.0. If a copy of the MPL was not distributed with this
%% file, You can obtain one at https://mozilla.org/MPL/2.0/.
%%
%% Copyright (c) 2007-2021 VMware, Inc. or its affiliates. All rights reserved.
%%
-module(rabbit_dead_letter).
-export([publish/5]).
-include("rabbit.hrl").
-include("rabbit_framing.hrl").
%%----------------------------------------------------------------------------
-type reason() :: 'expired' | 'rejected' | 'maxlen' | delivery_limit.
%%----------------------------------------------------------------------------
-spec publish(rabbit_types:message(), reason(), rabbit_types:exchange(),
'undefined' | binary(), rabbit_amqqueue:name()) -> 'ok'.
publish(Msg, Reason, X, RK, QName) ->
DLMsg = make_msg(Msg, Reason, X#exchange.name, RK, QName),
Delivery = rabbit_basic:delivery(false, false, DLMsg, undefined),
{Queues, Cycles} = detect_cycles(Reason, DLMsg,
rabbit_exchange:route(X, Delivery)),
lists:foreach(fun log_cycle_once/1, Cycles),
_ = rabbit_queue_type:deliver(rabbit_amqqueue:lookup(Queues),
Delivery, stateless),
ok.
make_msg(Msg = #basic_message{content = Content,
exchange_name = Exchange,
routing_keys = RoutingKeys},
Reason, DLX, RK, #resource{name = QName}) ->
{DeathRoutingKeys, HeadersFun1} =
case RK of
undefined -> {RoutingKeys, fun (H) -> H end};
_ -> {[RK], fun (H) -> lists:keydelete(<<"CC">>, 1, H) end}
end,
ReasonBin = list_to_binary(atom_to_list(Reason)),
TimeSec = os:system_time(seconds),
PerMsgTTL = per_msg_ttl_header(Content#content.properties),
HeadersFun2 =
fun (Headers) ->
%% The first routing key is the one specified in the
%% basic.publish; all others are CC or BCC keys.
RKs = [hd(RoutingKeys) | rabbit_basic:header_routes(Headers)],
RKs1 = [{longstr, Key} || Key <- RKs],
Info = [{<<"reason">>, longstr, ReasonBin},
{<<"queue">>, longstr, QName},
{<<"time">>, timestamp, TimeSec},
{<<"exchange">>, longstr, Exchange#resource.name},
{<<"routing-keys">>, array, RKs1}] ++ PerMsgTTL,
HeadersFun1(update_x_death_header(Info, Headers))
end,
Content1 = #content{properties = Props} =
rabbit_basic:map_headers(HeadersFun2, Content),
Content2 = Content1#content{properties =
Props#'P_basic'{expiration = undefined}},
Msg#basic_message{exchange_name = DLX,
id = rabbit_guid:gen(),
routing_keys = DeathRoutingKeys,
content = Content2}.
x_death_event_key(Info, Key) ->
case lists:keysearch(Key, 1, Info) of
false -> undefined;
{value, {Key, _KeyType, Val}} -> Val
end.
maybe_append_to_event_group(Table, _Key, _SeenKeys, []) ->
[Table];
maybe_append_to_event_group(Table, {_Queue, _Reason} = Key, SeenKeys, Acc) ->
case sets:is_element(Key, SeenKeys) of
true -> Acc;
false -> [Table | Acc]
end.
group_by_queue_and_reason([]) ->
[];
group_by_queue_and_reason([Table]) ->
[Table];
group_by_queue_and_reason(Tables) ->
{_, Grouped} =
lists:foldl(
fun ({table, Info}, {SeenKeys, Acc}) ->
Q = x_death_event_key(Info, <<"queue">>),
R = x_death_event_key(Info, <<"reason">>),
Matcher = queue_and_reason_matcher(Q, R),
{Matches, _} = lists:partition(Matcher, Tables),
{Augmented, N} = case Matches of
[X] -> {X, 1};
[X|_] = Xs -> {X, length(Xs)}
end,
Key = {Q, R},
Acc1 = maybe_append_to_event_group(
ensure_xdeath_event_count(Augmented, N),
Key, SeenKeys, Acc),
{sets:add_element(Key, SeenKeys), Acc1}
end, {sets:new(), []}, Tables),
Grouped.
update_x_death_header(Info, undefined) ->
update_x_death_header(Info, []);
update_x_death_header(Info, Headers) ->
X = x_death_event_key(Info, <<"exchange">>),
Q = x_death_event_key(Info, <<"queue">>),
R = x_death_event_key(Info, <<"reason">>),
case rabbit_basic:header(<<"x-death">>, Headers) of
undefined ->
%% First x-death event gets its own top-level headers.
%% See rabbitmq/rabbitmq-server#1332.
Headers2 = rabbit_misc:set_table_value(Headers, <<"x-first-death-reason">>,
longstr, R),
Headers3 = rabbit_misc:set_table_value(Headers2, <<"x-first-death-queue">>,
longstr, Q),
Headers4 = rabbit_misc:set_table_value(Headers3, <<"x-first-death-exchange">>,
longstr, X),
rabbit_basic:prepend_table_header(
<<"x-death">>,
[{<<"count">>, long, 1} | Info], Headers4);
{<<"x-death">>, array, Tables} ->
%% group existing x-death headers in case we have some from
%% before rabbitmq-server#78
GroupedTables = group_by_queue_and_reason(Tables),
{Matches, Others} = lists:partition(
queue_and_reason_matcher(Q, R),
GroupedTables),
Info1 = case Matches of
[] ->
[{<<"count">>, long, 1} | Info];
[{table, M}] ->
increment_xdeath_event_count(M)
end,
rabbit_misc:set_table_value(
Headers, <<"x-death">>, array,
[{table, rabbit_misc:sort_field_table(Info1)} | Others]);
{<<"x-death">>, InvalidType, Header} ->
rabbit_log:warning("Message has invalid x-death header (type: ~p)."
" Resetting header ~p",
[InvalidType, Header]),
%% if x-death is something other than an array (list)
%% then we reset it: this happens when some clients consume
%% a message and re-publish is, converting header values
%% to strings, intentionally or not.
%% See rabbitmq/rabbitmq-server#767 for details.
rabbit_misc:set_table_value(
Headers, <<"x-death">>, array,
[{table, [{<<"count">>, long, 1} | Info]}])
end.
ensure_xdeath_event_count({table, Info}, InitialVal) when InitialVal >= 1 ->
{table, ensure_xdeath_event_count(Info, InitialVal)};
ensure_xdeath_event_count(Info, InitialVal) when InitialVal >= 1 ->
case x_death_event_key(Info, <<"count">>) of
undefined ->
[{<<"count">>, long, InitialVal} | Info];
_ ->
Info
end.
increment_xdeath_event_count(Info) ->
case x_death_event_key(Info, <<"count">>) of
undefined ->
[{<<"count">>, long, 1} | Info];
N ->
lists:keyreplace(
<<"count">>, 1, Info,
{<<"count">>, long, N + 1})
end.
queue_and_reason_matcher(Q, R) ->
F = fun(Info) ->
x_death_event_key(Info, <<"queue">>) =:= Q
andalso x_death_event_key(Info, <<"reason">>) =:= R
end,
fun({table, Info}) ->
F(Info);
(Info) when is_list(Info) ->
F(Info)
end.
per_msg_ttl_header(#'P_basic'{expiration = undefined}) ->
[];
per_msg_ttl_header(#'P_basic'{expiration = Expiration}) ->
[{<<"original-expiration">>, longstr, Expiration}];
per_msg_ttl_header(_) ->
[].
detect_cycles(rejected, _Msg, Queues) ->
{Queues, []};
detect_cycles(_Reason, #basic_message{content = Content}, Queues) ->
#content{properties = #'P_basic'{headers = Headers}} =
rabbit_binary_parser:ensure_content_decoded(Content),
NoCycles = {Queues, []},
case Headers of
undefined ->
NoCycles;
_ ->
case rabbit_misc:table_lookup(Headers, <<"x-death">>) of
{array, Deaths} ->
{Cycling, NotCycling} =
lists:partition(fun (#resource{name = Queue}) ->
is_cycle(Queue, Deaths)
end, Queues),
OldQueues = [rabbit_misc:table_lookup(D, <<"queue">>) ||
{table, D} <- Deaths],
OldQueues1 = [QName || {longstr, QName} <- OldQueues],
{NotCycling, [[QName | OldQueues1] ||
#resource{name = QName} <- Cycling]};
_ ->
NoCycles
end
end.
is_cycle(Queue, Deaths) ->
{Cycle, Rest} =
lists:splitwith(
fun ({table, D}) ->
{longstr, Queue} =/= rabbit_misc:table_lookup(D, <<"queue">>);
(_) ->
true
end, Deaths),
%% Is there a cycle, and if so, is it "fully automatic", i.e. with
%% no reject in it?
case Rest of
[] -> false;
[H|_] -> lists:all(
fun ({table, D}) ->
{longstr, <<"rejected">>} =/=
rabbit_misc:table_lookup(D, <<"reason">>);
(_) ->
%% There was something we didn't expect, therefore
%% a client must have put it there, therefore the
%% cycle was not "fully automatic".
false
end, Cycle ++ [H])
end.
log_cycle_once(Queues) ->
Key = {queue_cycle, Queues},
case get(Key) of
true -> ok;
undefined -> rabbit_log:warning(
"Message dropped. Dead-letter queues cycle detected" ++
": ~p~nThis cycle will NOT be reported again.",
[Queues]),
put(Key, true)
end.
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