On 08/29/2014 03:42 PM, Rob Godfrey wrote:
The to field indicates the destination in terms of what the sender wants to
send it to. It says nothing about where it actually arrives.
"The to field identifies the node that is the intended
destination of the message. On any given transfer this
might not be the node at the receiving end of the link."
"Examples of AMQP nodes are producers, consumers, and
queues."
I can certainly see that it is useful to 'redirect' messages, i.e. to
deliver them to nodes other than that 'identified' as the 'destination'.
I can also certainly see that you might want a looser interpretation of
the to field to be some sort of abstract or logical description of
'message content and purpose' rather than the identity of a specific node.
I'm not opposed to change. However I don't think the use of subject for
what might be termed 'routing' is obviously wrong or unintended by the
current spec and therefore an illogical choice for anything 'designed
around AMQP 1.0'.
As an example let's take a simple news service. Senders send in some
news, recipients subscribe to receive news. Messages are classified with
regard to the type of news, e.g. sports, weather, politics whatever.
In such a case I think it would be a perfectly understandable choice
given the current spec to specify the type of news, the classification,
in the subject. It is after all clearly indicating in a brief way the
content and purpose of the news.
The c++ broker uses the subject when routing through pre 1.0 style
exchanges because that's what the only document on the subject - namely
the legacy filters, defined 'to allow a consistent mechanism for
addressing legacy AMQP Exchanges over AMQP 1.0' - specifies.
There may be good reasons to change this and reinterpret the property
descriptions. I don't think the wording of the current specification is
one of them.
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