Subscription to headers exchange via STOMP

[Tim Russell]

Hello,

I'm using RabbitMQ 3.5.1 and attempting to subscribe to a headers exchange with STOMP over a websocket (specifically, using http://jmesnil.net/stomp-websocket/doc/).

var websocket = new SockJS('https://server:15674/stomp');
var stompClient = Stomp.over(websocket);
stompClient.connect(headers, onConnect, onError);

var subscription = stompClient.subscribe("/exchange/my-event-exchange", function(event) {...}, {'x-match': 'all', abc: 'def', zzz: '124', id: '82979d0c-bc37-4bef-920f-45e99c0c7e43', persistent: true});

A SUBSCRIBE frame is successfully sent, but the filter headers ("abc" and "zzz" here) are essentially ignored.

DEBUG: >>> SUBSCRIBE
abc:def
zzz:125
x-match:all
id:82979d0c-bc37-4bef-920f-45e99c0c7e43
persistent:true
destination:/exchange/my-event-exchange

Instead of receiving only messages that match that pattern, the subscription receives all messages sent to the exchange.

I took a look at the source code that appears to handle this (https://github.com/rabbitmq/rabbitmq-stomp/blob/master/src/rabbit_stomp_processor.erl). I don't have any experience with Erlang, but it appears that line 604 sends the SUBSCRIBE frame without any arguments; I think this is where the filtering arguments would be getting sent if this were to work properly.

Is what I'm attempting currently possible?

Thanks!

[Alvaro Videla]

Hi,

From what I understand from this code: https://github.com/rabbitmq/rabbitmq-stomp/blob/master/src/rabbit_stomp_processor.erl#L606 and the rabbit_ensure_binding/3 function, STOMP doesn't handle header exchange bindings; it only uses bindings with routing keys.

See: https://github.com/rabbitmq/rabbitmq-erlang-client/blob/master/src/rabbit_routing_util.erl#L136

BTW: the subscribe command you see there in the Erlang code is just a queue subscription or "start consuming from a queue", it's not related to bindings.

Regards,

Alvaro

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[Michael Klishin]

 On 27 May 2015 at 11:02:25, Alvaro Videla (videl...@gmail.com) wrote:
> From what I understand from this code: https://github.com/rabbitmq/rabbitmq-stomp/blob/master/src/rabbit_stomp_processor.erl#L606
> and the rabbit_ensure_binding/3 function, STOMP doesn't handle
> header exchange bindings; it only uses bindings with routing
> keys.

and for "and" clauses ("x-match": "all"), a headers exchange can be fairly trivially
emulated with a topic one: just concatenate all values with a dot or other URI-safe
separator.
--
MK

Staff Software Engineer, Pivotal/RabbitMQ

[Tim Russell]

Thanks, Alvaro. You're totally right on the subscribe vs. binding. Not sure if you can answer this, but is it fair to say that STOMP precludes header exchange bindings, or is this simply a limitation of the current RabbitMQ STOMP adapter and/or the ensure_binding method?

[Tim Russell]

Thanks Michael. While I like how explicitly the headers exchange binding keys work (and the fact that, I think, the keys are order-neutral) I may just do this!

[Michael Klishin]

STOMP the protocol assumes topic exchange style routing.

MK

[Tim Russell]

Thanks. Topic exchange it is!