Extensions to BQ

1 files changed, 27 insertions, 10 deletions

diff --git a/src/rabbit_backing_queue.erl b/src/rabbit_backing_queue.erl
index 0ca8d260..0955a080 100644
--- a/src/rabbit_backing_queue.erl
+++ b/src/rabbit_backing_queue.erl
@@ -35,19 +35,18 @@ behaviour_info(callbacks) ->
      %% Initialise the backing queue and its state.
      %%
      %% Takes
-     %% 1. the queue name
-     %% 2. a boolean indicating whether the queue is durable
-     %% 3. a boolean indicating whether the queue is an existing queue
+     %% 1. the amqqueue record
+     %% 2. a boolean indicating whether the queue is an existing queue
      %%    that should be recovered
-     %% 4. an asynchronous callback which accepts a function of type
+     %% 3. an asynchronous callback which accepts a function of type
      %%    backing-queue-state to backing-queue-state. This callback
      %%    function can be safely invoked from any process, which
      %%    makes it useful for passing messages back into the backing
      %%    queue, especially as the backing queue does not have
      %%    control of its own mailbox.
-     %% 5. a synchronous callback. Same as the asynchronous callback
+     %% 4. a synchronous callback. Same as the asynchronous callback
      %%    but waits for completion and returns 'error' on error.
-     {init, 5},
+     {init, 4},
 
      %% Called on queue shutdown when queue isn't being deleted.
      {terminate, 1},
@@ -61,12 +60,12 @@ behaviour_info(callbacks) ->
      {purge, 1},
 
      %% Publish a message.
-     {publish, 3},
+     {publish, 4},
 
      %% Called for messages which have already been passed straight
      %% out to a client. The queue will be empty for these calls
      %% (i.e. saves the round trip through the backing queue).
-     {publish_delivered, 4},
+     {publish_delivered, 5},
 
      %% Return ids of messages which have been confirmed since
      %% the last invocation of this function (or initialisation).
@@ -109,7 +108,7 @@ behaviour_info(callbacks) ->
      {ack, 2},
 
      %% A publish, but in the context of a transaction.
-     {tx_publish, 4},
+     {tx_publish, 5},
 
      %% Acks, but in the context of a transaction.
      {tx_ack, 3},
@@ -165,7 +164,25 @@ behaviour_info(callbacks) ->
 
      %% Exists for debugging purposes, to be able to expose state via
      %% rabbitmqctl list_queues backing_queue_status
-     {status, 1}
+     {status, 1},
+
+     %% Passed a function to be invoked with the relevant backing
+     %% queue's state. Useful for when the backing queue or other
+     %% components need to pass functions into the backing queue.
+     {invoke, 3},
+
+     %% Called prior to a publish or publish_delivered call. Allows
+     %% the BQ to signal that it's already seen this message (and in
+     %% what capacity - i.e. was it published previously or discarded
+     %% previously) and thus the message should be dropped.
+     {is_duplicate, 3},
+
+     %% Called to inform the BQ about messages which have reached the
+     %% queue, but are not going to be further passed to BQ for some
+     %% reason. Note that this is may be invoked for messages for
+     %% which BQ:is_duplicate/2 has already returned {'published' |
+     %% 'discarded', BQS}.
+     {discard, 3}
     ];
 behaviour_info(_Other) ->
     undefined.