diff options
Diffstat (limited to 'src/rabbit_backing_queue.erl')
| -rw-r--r-- | src/rabbit_backing_queue.erl | 47 |
1 files changed, 45 insertions, 2 deletions
diff --git a/src/rabbit_backing_queue.erl b/src/rabbit_backing_queue.erl index 6a21e10f..0ca8d260 100644 --- a/src/rabbit_backing_queue.erl +++ b/src/rabbit_backing_queue.erl @@ -33,7 +33,21 @@ behaviour_info(callbacks) -> {stop, 0}, %% Initialise the backing queue and its state. - {init, 3}, + %% + %% 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 + %% that should be recovered + %% 4. 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 + %% but waits for completion and returns 'error' on error. + {init, 5}, %% Called on queue shutdown when queue isn't being deleted. {terminate, 1}, @@ -54,6 +68,35 @@ behaviour_info(callbacks) -> %% (i.e. saves the round trip through the backing queue). {publish_delivered, 4}, + %% Return ids of messages which have been confirmed since + %% the last invocation of this function (or initialisation). + %% + %% Message ids should only appear in the result of + %% drain_confirmed under the following circumstances: + %% + %% 1. The message appears in a call to publish_delivered/4 and + %% the first argument (ack_required) is false; or + %% 2. The message is fetched from the queue with fetch/2 and the + %% first argument (ack_required) is false; or + %% 3. The message is acked (ack/2 is called for the message); or + %% 4. The message is fully fsync'd to disk in such a way that the + %% recovery of the message is guaranteed in the event of a + %% crash of this rabbit node (excluding hardware failure). + %% + %% In addition to the above conditions, a message id may only + %% appear in the result of drain_confirmed if + %% #message_properties.needs_confirming = true when the msg was + %% published (through whichever means) to the backing queue. + %% + %% It is legal for the same message id to appear in the results + %% of multiple calls to drain_confirmed, which means that the + %% backing queue is not required to keep track of which messages + %% it has already confirmed. The confirm will be issued to the + %% publisher the first time the message id appears in the result + %% of drain_confirmed. All subsequent appearances of that message + %% id will be ignored. + {drain_confirmed, 1}, + %% Drop messages from the head of the queue while the supplied %% predicate returns true. {dropwhile, 2}, @@ -62,7 +105,7 @@ behaviour_info(callbacks) -> {fetch, 2}, %% Acktags supplied are for messages which can now be forgotten - %% about. Must return 1 guid per Ack, in the same order as Acks. + %% about. Must return 1 msg_id per Ack, in the same order as Acks. {ack, 2}, %% A publish, but in the context of a transaction. |