RE: [amqp-comment] amqp over http draft

[Clemens Vasters <clemensv@microsoft.com>]

When I have a multiplexing endpoint that accepts regular messages for one-way flows and that also responds to HTTP requests, I know that I have an HTTP request only when the HTTP request tells me that it is one. You appear to be advocating for my application having to use all sorts of hints to infer for a message to be an HTTP request, and the design in place makes a clear statement about it. If the core of your objection is about simplicity, I don't see how omitting a clear indicator is helping simplicity or how moving that indicator into a property that's aimed at the middleware layer will help simplicity.

This doesn't seem to be awfully hard:

If (msg.properties.subject.startswith(HTTP_REQUEST_PREFIX) )
{
       var method = msg.properties.subject.substring(HTTP_REQUEST_PREFIX_LENGTH);
       switch (method) 
       {
            .... handlers ....
       }
}


-----Original Message-----
From: Gordon Sim <gsim@redhat.com> 
Sent: Freitag, 24. Mai 2019 11:12
To: amqp-comment@lists.oasis-open.org
Subject: Re: [amqp-comment] amqp over http draft

On 24/05/2019 8:13 am, Clemens Vasters wrote:
> The projected mode is specifically designed to preserve HTTP semantics 
> at the request-level, and if I have an endpoint that accepts HTTP 
> requests but then also accepts other messages, I need to distinguish 
> the two kinds of messages.

Why? At the point you are accepting HTTP you know it is HTTP. At the point you are handling the AMQP message, the details of that messages should be sufficient. It has the target address, any headers, the method etc and can be converted back to HTTP if needed by the ultimate recipient.

> Polluting the application-properties is not optimal, because that's 
> where all the HTTP headers go that aren't otherwise explicitly mapped 
> and since we aim to be transparent, I can't really reserve a name in 
> that section.

To me it is not necessary in the application-properties either, but is is much less optimal to have it as a prefix in the subject where it infects every AMQP application involved. That will really limit the appeal of this spec.

What about defining a message-annotation that you can add if you want to know the protocol that caused the generation of the message?


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