[Date Prev] | [Thread Prev] | [Thread Next] | [Date Next] -- [Date Index] | [Thread Index] | [List Home]
Subject: Re: [sca-assembly] [Issue 251] Some early thoughts
A quick response to this: On 12/14/10 12:41 AM, Anish Karmarkar wrote: > The pub-sub model is different than this. A consumer may express > interest in certain events, but there is absolutely no guarantee that > an event may ever be delivered to it. Similarly, a producer may > produce events, but there is not guarantee that any consumer is either > listening for those events or even if a consumer is listening, it may > decide to just drop it on the floor and not take any action based on > that event. Furthermore, these kind of connections are meant to be > many-to-many. As far as cardinality goes, the cardinality has to be > wrt how many channels the producer/consumer is connected to regardless > of how many consumer/producers are on those channels. This makes > cardinality in pub-sub tricky. As far as cardinality upper bound goes, > what is the difference between a consumer connected to 2 channels each > with 5 producers and the same consumer connected to a single channel > with 10 producers? Seems like the above notion confuses the M-to-N relationship of (publishers & subscribers) "attached" to a channel, with the different scenario of attaching a producer to multiple channels. With the latter, in the generic case, the runtime will likely need to send messages to both channels - thus a receiving consumer will see the same message *twice* because a producer is wired to two channels, and the consumer is wired to the same two channels. Consequently, I see a dramatic difference between allowing a consumer to consume from multiple channels, and allowing both a producer and a consumer to attach to multiple channels. In the second case, I'm guaranteeing the ability to achieve a relatively useless outcome - a consumer who is ("best effort", or whatever quality of service is in use) guaranteed to receive two or more copies of the same event. Why? -Eric.