From 250667f80cffb7f6a63d049e1480df42d7460b6f Mon Sep 17 00:00:00 2001
From: Simon MacMullen <simon@rabbitmq.com>
Date: Fri, 5 Dec 2014 14:44:31 +0000
Subject: Introduce a selection mechanism so that small messages go to the
 index, and large ones go to the store.

---
 ebin/rabbit_app.in            |  1 +
 src/rabbit_variable_queue.erl | 46 +++++++++++++++++++++++++++++++------------
 2 files changed, 34 insertions(+), 13 deletions(-)

diff --git a/ebin/rabbit_app.in b/ebin/rabbit_app.in
index 9e5584a1..5ebef608 100644
--- a/ebin/rabbit_app.in
+++ b/ebin/rabbit_app.in
@@ -29,6 +29,7 @@
          {heartbeat, 580},
          {msg_store_file_size_limit, 16777216},
          {queue_index_max_journal_entries, 65536},
+         {queue_index_embed_msgs_below, 1024},
          {default_user, <<"guest">>},
          {default_pass, <<"guest">>},
          {default_user_tags, [administrator]},
diff --git a/src/rabbit_variable_queue.erl b/src/rabbit_variable_queue.erl
index 884342d8..7a7a2900 100644
--- a/src/rabbit_variable_queue.erl
+++ b/src/rabbit_variable_queue.erl
@@ -989,7 +989,11 @@ beta_msg_status0(SeqId, MsgProps, IsPersistent, IsDelivered) ->
               index_on_disk = true,
               msg_props     = MsgProps}.
 
-trim_msg_status(MsgStatus) -> MsgStatus.%% TODO #msg_status { msg = undefined }.
+trim_msg_status(MsgStatus = #msg_status{msg_props = MsgProps}) ->
+    case persist_to(MsgProps) of
+        msg_store   -> MsgStatus#msg_status{msg = undefined};
+        queue_index -> MsgStatus
+    end.
 
 with_msg_store_state({MSCStateP, MSCStateT},  true, Fun) ->
     {Result, MSCStateP1} = Fun(MSCStateP),
@@ -1325,14 +1329,15 @@ maybe_write_msg_to_disk(_Force, MsgStatus = #msg_status {
     MsgStatus;
 maybe_write_msg_to_disk(Force, MsgStatus = #msg_status {
                                  msg = Msg, msg_id = MsgId,
+                                 msg_props = MsgProps,
                                  is_persistent = IsPersistent }, MSCState)
   when Force orelse IsPersistent ->
-    %% Msg1 = Msg #basic_message {
-    %%          %% don't persist any recoverable decoded properties
-    %%          content = rabbit_binary_parser:clear_decoded_content(
-    %%                      Msg #basic_message.content)},
-    %% ok = msg_store_write(MSCState, IsPersistent, MsgId, Msg1),
-    MsgStatus; %% #msg_status { msg_on_disk = true };
+    case persist_to(MsgProps) of
+        msg_store   -> ok = msg_store_write(MSCState, IsPersistent, MsgId,
+                                            prepare_to_store(Msg)),
+                       MsgStatus#msg_status{msg_in_store = true};
+        queue_index -> MsgStatus
+    end;
 maybe_write_msg_to_disk(_Force, MsgStatus, _MSCState) ->
     MsgStatus.
 
@@ -1347,13 +1352,12 @@ maybe_write_index_to_disk(Force, MsgStatus = #msg_status {
                                    is_delivered  = IsDelivered,
                                    msg_props     = MsgProps}, IndexState)
   when Force orelse IsPersistent ->
-    Msg1 = Msg #basic_message {
-             %% don't persist any recoverable decoded properties
-             content = rabbit_binary_parser:clear_decoded_content(
-                         Msg #basic_message.content)},
     IndexState1 = rabbit_queue_index:publish(
-                    Msg1, SeqId, MsgProps, IsPersistent, IndexState),
-    {MsgStatus #msg_status { index_on_disk = true },
+                    case persist_to(MsgProps) of
+                        msg_store   -> MsgId;
+                        queue_index -> prepare_to_store(Msg)
+                    end, SeqId, MsgProps, IsPersistent, IndexState),
+    {MsgStatus#msg_status{index_on_disk = true},
      maybe_write_delivered(IsDelivered, SeqId, IndexState1)};
 maybe_write_index_to_disk(_Force, MsgStatus, IndexState) ->
     {MsgStatus, IndexState}.
@@ -1366,6 +1370,22 @@ maybe_write_to_disk(ForceMsg, ForceIndex, MsgStatus,
         maybe_write_index_to_disk(ForceIndex, MsgStatus1, IndexState),
     {MsgStatus2, State #vqstate { index_state = IndexState1 }}.
 
+persist_to(#message_properties{size = Size}) ->
+    {ok, IndexMaxSize} = application:get_env(
+                           rabbit, queue_index_embed_msgs_below),
+    %% This is >= so that you can set the env to 0 and never persist
+    %% to the index.
+    case Size >= IndexMaxSize of
+        true  -> msg_store;
+        false -> queue_index
+    end.
+
+prepare_to_store(Msg) ->
+    Msg#basic_message{
+      %% don't persist any recoverable decoded properties
+      content = rabbit_binary_parser:clear_decoded_content(
+                  Msg #basic_message.content)}.
+
 %%----------------------------------------------------------------------------
 %% Internal gubbins for acks
 %%----------------------------------------------------------------------------
-- 
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