[rabbitmq-discuss] Queue Re-declaration

Tue Jan 13 08:47:22 GMT 2009

Chuck,

Chuck Remes wrote:
> According to the 0-8 and 0-10 specs, if the queue already exists then  
> subsequent declarations with :durable and :auto-delete set ignore  
> those bits.

Correct.

> BTW, the same is true for exchanges.

Ditto.

> I could not find these provisions in the 0-9-1 spec which is odd.  
> However, I imagine these provisions hold true for it too.

Nope. The following rule has been added regarding the "passive" flag:

"If not set and the exchange exists, the server MUST check that the 
existing exchange has the same values for type, durable, and arguments 
fields.  The server MUST respond with Declare-Ok if the requested 
exchange matches these fields, and MUST raise a channel exception if not."

There is a similar rule for queues.

This corrects a flaw in the 0-8/9 version of the spec. Declarations are 
meant to be *assertions*, e.g. an exchange.declare should be read as "I 
assert that there shall be an exchange named X that is durable, etc". So 
it would be quite wrong for a declaration to return 'ok' when the 
existing entity does not have the specified settings.

Matthias.