Woops the wiki I am referring to is: https://wiki.openstack.org/wiki/Oslo/Messaging
William ----- Original Message ----- > Hi all, > I've been reading through the Messaging Wiki and have some comments. Not > criticisms, just comments and questions. > I have found this to be a very useful document. Thanks. > 1. "There are multiple backend transport drivers which implement the API > semantics using different messaging systems - e.g. RabbitMQ, Qpid, ZeroMQ. > While both sides of a connection must use the same transport driver > configured in the same way, the API avoids exposing details of transports so > that code written using one transport should work with any other transport." > The good news for AMQP 1.0 users is that technically "boths sides of the > connection" do not have to use same transport driver. In pre-AMQP 1.0 days > this was the case. But today interoperability between AMQP 1.0 > implementations has been demonstrated. > 2. I notice under the RPC concepts section that you mention Exchanges as a > container in which topics are scoped. Is this exchange a pre AMQP 1.0 > artifact or just a general term for oslo.messaging that is loosely based on > the pre-AMQP 1.0 artifact called an Exchange? i.e. are you assuming that > messaging implementations have something called an exchange? Or do you mean > that messaging implementations can scope a topic and in oslo we call that > scoping an exchange? > 3. Some messaging nomenclature: The way the wiki describes RPC " Invoke > Method on One of Multiple Servers " is more like a queue than a topic. In > messaging a queue is something that multiple consumers can attach to and one > of them gets and services a message/request. A topic is where 1+ consumers > are "connected" and each receives a the message and each can service it as > it sees fit. In pre-AMQP 1.0 terms what this seems to describe is a direct > exchange. And a direct excahnge can have multiple consumers listening to a > queue on that exchange. (Remember that fanout is just a generalization of > topic in that all consumers get all fanout messages - there are no > sub-topics etc.) > In AMQP 1.0 the addressing doesn't care or know about exchanges but it can > support this queue type behavior on an address or topic type behavior on an > address. > I know this isn't about AMQP specifically but therefore this is even more > important. Topics are pub/sub with multiple consumer/services responding to > a single message. Queues are next consumer up gets the next message. > (BTW I've seen this kind of confusion also in early versions of MCollective > in Puppet.) > It might be better to change some of the references to "topic" to "address". > This would solve the problem. i.e. a use case where one of many servers > listening on an address services a message/request. And later all of servers > listening on an address service a message/request. Addressing also solves > the one-to-one as the address is specific to the server (and the others > don't have to receive and reject the message). > Please feel free to respond and critique my comments/suggestions. > Best, > William > _______________________________________________ > OpenStack-dev mailing list > [email protected] > http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev
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