From ac86a6cad73cbcee0e94e65f245c5b89fffb220b Mon Sep 17 00:00:00 2001
From: kjnilsson <knilsson@pivotal.io>
Date: Tue, 25 Feb 2020 14:40:09 +0000
Subject: Fix QQ crash recovery bug

When using dead letter handlers the state machine would crash when a
prefix_msg was being dead-lettered on recovery. This handles this case
and also fixes an issue where the incorrect initial release cursor
interval would have been set when overriding the release cursor default.

[#171463230]
---
 src/rabbit_fifo.erl | 13 +++++++++----
 src/rabbit_fifo.hrl |  6 +++---
 2 files changed, 12 insertions(+), 7 deletions(-)

(limited to 'src')

diff --git a/src/rabbit_fifo.erl b/src/rabbit_fifo.erl
index 0917836b6a..251b370caa 100644
--- a/src/rabbit_fifo.erl
+++ b/src/rabbit_fifo.erl
@@ -146,7 +146,9 @@ update_config(Conf, State) ->
     SHICur = case State#?MODULE.cfg of
                  #cfg{release_cursor_interval = {_, C}} ->
                      C;
-                 #cfg{release_cursor_interval  = C} ->
+                 #cfg{release_cursor_interval = undefined} ->
+                     SHI;
+                 #cfg{release_cursor_interval = C} ->
                      C
              end,
 
@@ -1086,8 +1088,9 @@ snd(T) ->
 return(Meta, ConsumerId, Returned,
        Effects0, #?MODULE{service_queue = SQ0} = State0) ->
     {State1, Effects1} = maps:fold(
-                          fun(MsgId, {Tag, _} = Msg, {S0, E0}) when Tag == '$prefix_msg';
-                                                                    Tag == '$empty_msg'->
+                           fun(MsgId, {Tag, _} = Msg, {S0, E0})
+                                 when Tag == '$prefix_msg';
+                                      Tag == '$empty_msg'->
                                   return_one(MsgId, 0, Msg, S0, E0, ConsumerId);
                              (MsgId, {MsgNum, Msg}, {S0, E0}) ->
                                   return_one(MsgId, MsgNum, Msg, S0, E0,
@@ -1158,7 +1161,9 @@ dead_letter_effects(Reason, Discarded,
                     #?MODULE{cfg = #cfg{dead_letter_handler = {Mod, Fun, Args}}},
                     Effects) ->
     DeadLetters = maps:fold(fun(_, {_, {_, {_Header, Msg}}}, Acc) ->
-                                    [{Reason, Msg} | Acc]
+                                    [{Reason, Msg} | Acc];
+                               (_, _, Acc) ->
+                                    Acc
                             end, [], Discarded),
     [{mod_call, Mod, Fun, Args ++ [DeadLetters]} | Effects].
 
diff --git a/src/rabbit_fifo.hrl b/src/rabbit_fifo.hrl
index 16e665f9df..2fae8c10ca 100644
--- a/src/rabbit_fifo.hrl
+++ b/src/rabbit_fifo.hrl
@@ -104,9 +104,9 @@
 -record(cfg,
         {name :: atom(),
          resource :: rabbit_types:r('queue'),
-         release_cursor_interval =
-             {?RELEASE_CURSOR_EVERY, ?RELEASE_CURSOR_EVERY} ::
-             non_neg_integer() | {non_neg_integer(), non_neg_integer()},
+         release_cursor_interval ::
+             undefined | non_neg_integer() |
+             {non_neg_integer(), non_neg_integer()},
          dead_letter_handler :: option(applied_mfa()),
          become_leader_handler :: option(applied_mfa()),
          max_length :: option(non_neg_integer()),
-- 
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