Poison handling in quorum queues

Drop messages that exceed the configured number of delivery attemps.
If a DLX is configured, dead letter them.

[#163513253]

3 files changed, 56 insertions, 32 deletions

diff --git a/src/rabbit_fifo.erl b/src/rabbit_fifo.erl
index af3441df86..da9772516c 100644
--- a/src/rabbit_fifo.erl
+++ b/src/rabbit_fifo.erl
@@ -252,7 +252,8 @@
          consumer_strategy = default :: default | single_active,
          %% waiting consumers, one is picked active consumer is cancelled or dies
          %% used only when single active consumer is on
-         waiting_consumers = [] :: [{consumer_id(), consumer()}]
+         waiting_consumers = [] :: [{consumer_id(), consumer()}],
+         delivery_limit :: maybe(non_neg_integer())
         }).
 
 -opaque state() :: #state{}.
@@ -264,7 +265,8 @@
                     release_cursor_interval => non_neg_integer(),
                     max_length => non_neg_integer(),
                     max_bytes => non_neg_integer(),
-                    single_active_consumer_on => boolean()}.
+                    single_active_consumer_on => boolean(),
+                    delivery_limit => non_neg_integer()}.
 
 -export_type([protocol/0,
               delivery/0,
@@ -293,6 +295,7 @@ update_config(Conf, State) ->
     SHI = maps:get(release_cursor_interval, Conf, ?RELEASE_CURSOR_EVERY),
     MaxLength = maps:get(max_length, Conf, undefined),
     MaxBytes = maps:get(max_bytes, Conf, undefined),
+    DeliveryLimit = maps:get(delivery_limit, Conf, undefined),
     ConsumerStrategy = case maps:get(single_active_consumer_on, Conf, false) of
                            true ->
                                single_active;
@@ -304,7 +307,8 @@ update_config(Conf, State) ->
                 release_cursor_interval = SHI,
                 max_length = MaxLength,
                 max_bytes = MaxBytes,
-                consumer_strategy = ConsumerStrategy}.
+                consumer_strategy = ConsumerStrategy,
+                delivery_limit = DeliveryLimit}.
 
 zero(_) ->
     0.
@@ -468,10 +472,10 @@ apply(_, {down, ConsumerPid, noconnection},
                       #consumer{checked_out = Checked0} = C,
                       {Co, St0, Eff}) when (node(P) =:= Node) and
                                            (C#consumer.status =/= cancelled)->
-                          St = return_all(St0, Checked0),
+                          {St, Eff0} = return_all(St0, Checked0, Eff),
                           Credit = increase_credit(C, maps:size(Checked0)),
                           Eff1 = ConsumerUpdateActiveFun(St, K, C, false,
-                                                         suspected_down, Eff),
+                                                         suspected_down, Eff0),
                           {maps:put(K,
                                     C#consumer{status = suspected_down,
                                                credit = Credit,
@@ -961,8 +965,8 @@ maybe_return_all(ConsumerId, #consumer{checked_out = Checked0} = Consumer, Cons1
                                      C0, SQ0, Effects0),
             {S0#state{consumers = Cons, service_queue = SQ}, Effects1};
         down ->
-            S1 = return_all(S0, Checked0),
-            {S1#state{consumers = Cons1}, Effects0}
+            {S1, Effects1} = return_all(S0, Checked0, Effects0),
+            {S1#state{consumers = Cons1}, Effects1}
     end.
 
 apply_enqueue(#{index := RaftIdx} = Meta, From, Seq, RawMsg, State0) ->
@@ -1082,16 +1086,16 @@ return(Meta, ConsumerId, MsgNumMsgs, Con0, Checked,
        Effects0, #state{consumers = Cons0, service_queue = SQ0} = State0) ->
     Con = Con0#consumer{checked_out = Checked,
                         credit = increase_credit(Con0, length(MsgNumMsgs))},
-    {Cons, SQ, Effects} = update_or_remove_sub(ConsumerId, Con, Cons0,
+    {Cons, SQ, Effects1} = update_or_remove_sub(ConsumerId, Con, Cons0,
                                                SQ0, Effects0),
-    State1 = lists:foldl(fun({'$prefix_msg', _} = Msg, S0) ->
-                                 return_one(0, Msg, S0);
-                            ({MsgNum, Msg}, S0) ->
-                                 return_one(MsgNum, Msg, S0)
-                         end, State0, MsgNumMsgs),
+    {State1, Effects2} = lists:foldl(fun({'$prefix_msg', _} = Msg, {S0, E0}) ->
+                                             return_one(0, Msg, S0, E0);
+                                        ({MsgNum, Msg}, {S0, E0}) ->
+                                             return_one(MsgNum, Msg, S0, E0)
+                                     end, {State0, Effects1}, MsgNumMsgs),
     checkout(Meta, State1#state{consumers = Cons,
                                 service_queue = SQ},
-             Effects).
+             Effects2).
 
 % used to processes messages that are finished
 complete(ConsumerId, MsgRaftIdxs, NumDiscarded,
@@ -1197,28 +1201,35 @@ find_next_cursor(Smallest, Cursors0, Potential) ->
     end.
 
 return_one(0, {'$prefix_msg', _} = Msg,
-           #state{returns = Returns} = State0) ->
-    add_bytes_return(Msg,
-                     State0#state{returns = lqueue:in(Msg, Returns)});
+           #state{returns = Returns} = State0, Effects) ->
+    {add_bytes_return(Msg,
+                      State0#state{returns = lqueue:in(Msg, Returns)}), Effects};
 return_one(MsgNum, {RaftId, {Header0, RawMsg}},
-           #state{returns = Returns} = State0) ->
+           #state{returns = Returns,
+                  delivery_limit = DeliveryLimit} = State0, Effects0) ->
     Header = maps:update_with(delivery_count,
                               fun (C) -> C+1 end,
                               1, Header0),
-    Msg = {RaftId, {Header, RawMsg}},
-    % this should not affect the release cursor in any way
-    add_bytes_return(RawMsg,
-                     State0#state{returns = lqueue:in({MsgNum, Msg}, Returns)}).
+    case maps:get(delivery_count, Header) of
+        DeliveryCount when DeliveryCount > DeliveryLimit ->
+            Effects = dead_letter_effects(rejected, maps:put(none, {MsgNum, {RaftId, {Header, RawMsg}}}, #{}), State0, Effects0),
+            {add_bytes_settle(RawMsg, State0), Effects};
+        _ ->
+            Msg = {RaftId, {Header, RawMsg}},
+            %% this should not affect the release cursor in any way
+            {add_bytes_return(RawMsg,
+                             State0#state{returns = lqueue:in({MsgNum, Msg}, Returns)}), Effects0}
+    end.
 
-return_all(State0, Checked0) ->
+return_all(State0, Checked0, Effects0) ->
     %% need to sort the list so that we return messages in the order
     %% they were checked out
     Checked = lists:sort(maps:to_list(Checked0)),
-    lists:foldl(fun ({_, {'$prefix_msg', _} = Msg}, S) ->
-                        return_one(0, Msg, S);
-                    ({_, {MsgNum, Msg}}, S) ->
-                        return_one(MsgNum, Msg, S)
-                end, State0, Checked).
+    lists:foldl(fun ({_, {'$prefix_msg', _} = Msg}, {S, E}) ->
+                        return_one(0, Msg, S, E);
+                    ({_, {MsgNum, Msg}}, {S, E}) ->
+                        return_one(MsgNum, Msg, S, E)
+                end, {State0, Effects0}, Checked).
 
 %% checkout new messages to consumers
 %% reverses the effects list
diff --git a/src/rabbit_policies.erl b/src/rabbit_policies.erl
index 555e4e2e87..95bf067539 100644
--- a/src/rabbit_policies.erl
+++ b/src/rabbit_policies.erl
@@ -43,14 +43,17 @@ register() ->
                           {policy_validator, <<"max-length-bytes">>},
                           {policy_validator, <<"queue-mode">>},
                           {policy_validator, <<"overflow">>},
+                          {policy_validator, <<"delivery-limit">>},
                           {operator_policy_validator, <<"expires">>},
                           {operator_policy_validator, <<"message-ttl">>},
                           {operator_policy_validator, <<"max-length">>},
                           {operator_policy_validator, <<"max-length-bytes">>},
+                          {operator_policy_validator, <<"delivery-limit">>},
                           {policy_merge_strategy, <<"expires">>},
                           {policy_merge_strategy, <<"message-ttl">>},
                           {policy_merge_strategy, <<"max-length">>},
-                          {policy_merge_strategy, <<"max-length-bytes">>}]],
+                          {policy_merge_strategy, <<"max-length-bytes">>},
+                          {policy_merge_strategy, <<"delivery-limit">>}]],
     ok.
 
 validate_policy(Terms) ->
@@ -111,9 +114,16 @@ validate_policy0(<<"overflow">>, <<"drop-head">>) ->
 validate_policy0(<<"overflow">>, <<"reject-publish">>) ->
     ok;
 validate_policy0(<<"overflow">>, Value) ->
-    {error, "~p is not a valid overflow value", [Value]}.
+    {error, "~p is not a valid overflow value", [Value]};
+
+validate_policy0(<<"delivery-limit">>, Value)
+  when is_integer(Value), Value >= 0 ->
+    ok;
+validate_policy0(<<"delivery-limit">>, Value) ->
+    {error, "~p is not a valid delivery limit", [Value]}.
 
 merge_policy_value(<<"message-ttl">>, Val, OpVal)      -> min(Val, OpVal);
 merge_policy_value(<<"max-length">>, Val, OpVal)       -> min(Val, OpVal);
 merge_policy_value(<<"max-length-bytes">>, Val, OpVal) -> min(Val, OpVal);
-merge_policy_value(<<"expires">>, Val, OpVal)          -> min(Val, OpVal).
+merge_policy_value(<<"expires">>, Val, OpVal)          -> min(Val, OpVal);
+merge_policy_value(<<"delivery-limit">>, Val, OpVal)   -> min(Val, OpVal).
diff --git a/src/rabbit_quorum_queue.erl b/src/rabbit_quorum_queue.erl
index 9e73981541..7c46170b8e 100644
--- a/src/rabbit_quorum_queue.erl
+++ b/src/rabbit_quorum_queue.erl
@@ -163,13 +163,16 @@ ra_machine_config(Q) when ?is_amqqueue(Q) ->
     %% take the minimum value of the policy and the queue arg if present
     MaxLength = args_policy_lookup(<<"max-length">>, fun min/2, Q),
     MaxBytes = args_policy_lookup(<<"max-length-bytes">>, fun min/2, Q),
+    DeliveryLimit = args_policy_lookup(<<"delivery-limit">>, fun min/2, Q),
     #{name => Name,
       queue_resource => QName,
       dead_letter_handler => dlx_mfa(Q),
       become_leader_handler => {?MODULE, become_leader, [QName]},
       max_length => MaxLength,
       max_bytes => MaxBytes,
-      single_active_consumer_on => single_active_consumer_on(Q)}.
+      single_active_consumer_on => single_active_consumer_on(Q),
+      delivery_limit => DeliveryLimit
+     }.
 
 single_active_consumer_on(Q) ->
     QArguments = amqqueue:get_arguments(Q),