From 34290816e2bdfe4205bda82c6ae95aafef319d65 Mon Sep 17 00:00:00 2001
From: Matthias Radestock <matthias@rabbitmq.com>
Date: Thu, 20 Jan 2011 23:12:42 +0000
Subject: move channel lookups into handle_ methods This avoids double lookup
 in some paths and unnecessary invocations of run_message_queue. Also inline
 recorde_current_channel_tx, which eliminates some lookup. And allow rollback
 to trigger the forgetting of a channel record.

---
 src/rabbit_amqqueue_process.erl | 72 +++++++++++++++++------------------------
 1 file changed, 29 insertions(+), 43 deletions(-)

diff --git a/src/rabbit_amqqueue_process.erl b/src/rabbit_amqqueue_process.erl
index 48192dcb..0346ec7d 100644
--- a/src/rabbit_amqqueue_process.erl
+++ b/src/rabbit_amqqueue_process.erl
@@ -332,11 +332,6 @@ ch_record_state_transition(OldCR, NewCR) ->
        true                               -> ok
     end.
 
-record_current_channel_tx(ChPid, Txn) ->
-    %% as a side effect this also starts monitoring the channel (if
-    %% that wasn't happening already)
-    store_ch_record((ch_record(ChPid))#cr{txn = Txn}).
-
 deliver_msgs_to_consumers(Funs = {PredFun, DeliverFun}, FunAcc,
                           State = #q{q = #amqqueue{name = QName},
                                      active_consumers = ActiveConsumers,
@@ -495,7 +490,7 @@ attempt_delivery(#delivery{txn = Txn,
                  {NeedsConfirming,
                   State = #q{backing_queue = BQ,
                             backing_queue_state = BQS}}) ->
-    record_current_channel_tx(ChPid, Txn),
+    store_ch_record((ch_record(ChPid))#cr{txn = Txn}),
     {true,
      NeedsConfirming,
      State#q{backing_queue_state =
@@ -591,7 +586,7 @@ handle_ch_down(DownPid, State = #q{exclusive_consumer = Holder}) ->
                 true  -> {stop, State1};
                 false -> State2 = case Txn of
                                       none -> State1;
-                                      _    -> rollback_transaction(Txn, ChPid,
+                                      _    -> rollback_transaction(Txn, C,
                                                                    State1)
                                   end,
                          {ok, requeue_and_run(sets:to_list(ChAckTags),
@@ -627,39 +622,24 @@ maybe_run_queue_via_backing_queue(Fun, State = #q{backing_queue_state = BQS}) ->
     run_message_queue(
       confirm_messages(Guids, State#q{backing_queue_state = BQS1})).
 
-commit_transaction(Txn, From, ChPid, State = #q{backing_queue       = BQ,
-                                                backing_queue_state = BQS,
-                                                ttl                 = TTL}) ->
-    %% ChPid must be known here because of the participant management
-    %% by the channel. However, in a cluster, the DOWN can overtake
-    %% the commit, and so there is a case where handle_ch_down has
-    %% already been called for ChPid.
-    case lookup_ch(ChPid) of
-        not_found ->
-            gen_server2:reply(From, ok),
-            State;
-        C = #cr{acktags = ChAckTags} ->
-            {AckTags, BQS1} = BQ:tx_commit(
-                                Txn, fun () -> gen_server2:reply(From, ok) end,
-                                reset_msg_expiry_fun(TTL), BQS),
-            ChAckTags1 = subtract_acks(ChAckTags, AckTags),
-            maybe_store_ch_record(C#cr{acktags = ChAckTags1, txn = none}),
-            State#q{backing_queue_state = BQS1}
-    end.
-
-rollback_transaction(Txn, ChPid, State = #q{backing_queue = BQ,
-                                            backing_queue_state = BQS}) ->
-    case lookup_ch(ChPid) of
-        not_found ->
-            State;
-        #cr{} ->
-            {_AckTags, BQS1} = BQ:tx_rollback(Txn, BQS),
-            %% Iff we removed acktags from the channel record on
-            %% ack+txn then we would add them back in here (would also
-            %% require ChPid)
-            record_current_channel_tx(ChPid, none),
-            State#q{backing_queue_state = BQS1}
-    end.
+commit_transaction(Txn, From, C = #cr{acktags = ChAckTags},
+                   State = #q{backing_queue       = BQ,
+                              backing_queue_state = BQS,
+                              ttl                 = TTL}) ->
+    {AckTags, BQS1} = BQ:tx_commit(
+                        Txn, fun () -> gen_server2:reply(From, ok) end,
+                        reset_msg_expiry_fun(TTL), BQS),
+    ChAckTags1 = subtract_acks(ChAckTags, AckTags),
+    maybe_store_ch_record(C#cr{acktags = ChAckTags1, txn = none}),
+    State#q{backing_queue_state = BQS1}.
+
+rollback_transaction(Txn, C, State = #q{backing_queue = BQ,
+                                        backing_queue_state = BQS}) ->
+    {_AckTags, BQS1} = BQ:tx_rollback(Txn, BQS),
+    %% Iff we removed acktags from the channel record on ack+txn then
+    %% we would add them back in here.
+    maybe_store_ch_record(C#cr{txn = none}),
+    State#q{backing_queue_state = BQS1}.
 
 subtract_acks(A, B) when is_list(B) ->
     lists:foldl(fun sets:del_element/2, A, B).
@@ -860,8 +840,11 @@ handle_call({deliver, Delivery}, From, State) ->
     noreply(NewState);
 
 handle_call({commit, Txn, ChPid}, From, State) ->
-    NewState = commit_transaction(Txn, From, ChPid, State),
-    noreply(run_message_queue(NewState));
+    case lookup_ch(ChPid) of
+        not_found -> reply(ok, State);
+        C         -> noreply(run_message_queue(
+                               commit_transaction(Txn, From, C, State)))
+    end;
 
 handle_call({notify_down, ChPid}, _From, State) ->
     %% we want to do this synchronously, so that auto_deleted queues
@@ -1060,7 +1043,10 @@ handle_cast({reject, AckTags, Requeue, ChPid},
     end;
 
 handle_cast({rollback, Txn, ChPid}, State) ->
-    noreply(rollback_transaction(Txn, ChPid, State));
+    noreply(case lookup_ch(ChPid) of
+                not_found -> State;
+                C         -> rollback_transaction(Txn, C, State)
+            end);
 
 handle_cast(delete_immediately, State) ->
     {stop, normal, State};
-- 
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