[rabbitmq-discuss] Publish to queue fails but publish to direct exchange works

[Matthias Radestock]

Raphael,

Raphael Simon wrote:
> <matthias at rabbitmq.com <mailto:matthias at rabbitmq.com>> wrote:
>     Simply running 'rabbitmqctl list_bindings' should give the same
>     results. Please do that, just to check.
> 
> Yes indeed but where is the fun in doing that? OK more seriously I did 
> not understand the subtlety of the empty spaces, now I do (as a side 
> note it would be nice to have something rather than blank in this case 
> maybe *** or ---).

The reason we don't map the blank exchange name to something else is 
that RabbitMQ permits anything in the exchange name, so *** and --- 
actually are valid exchange names.

> I can't think of a place where we would delete a binding. We only 
> ever delete queues.

Are all AMQP interactions going through nanite? I can see there aren't 
any queue.unbind actions in that code base.

>     Is this reproducible at all? I suspect not :(
> 
> No it has only happens about 15 times on the course of two days. During 
> these two days our system was having issues and weird things could have 
> happened on the broker (e.g. the queue could have been deleted and 
> recreated).

Queue creation and deletion, and all they entail, e.g. addition/removal 
of the default bindings, are meant to be atomic. And the code dealing 
with that looks correct. But ...

>     What version of rabbit are you running?
> 
> 1.7.2

I suggest you upgrade. The queue and exchange code has changed quite a 
bit in the recent release. While I do not recall us spotting any 
problems in the previous version that would explain the behaviour you 
are seeing, it is nevertheless possible that there was a bug in the 
previous code which has been eradicated by other changes.

>     Interesting. auto-delete exchanges are very rare. In fact I do not
>     know of anybody else using them. So it's possible there is a bug in
>     that code that has laid dormant for years. Can you explain your
>     use-case for auto-delete exchanges?
> 
> Embarrassingly enough, I can't :) The fact that we are using direct 
> exchanges for these queues was a bug we introduced, we will be removing 
> them.

ok. If you *do* think of a use case for auto-delete exchanges, please 
let us know. The AMQP 0-9-1 spec actually removes that feature, but we 
are having second thoughts on whether that was the right thing to do.

> I recreated some bindings from within the broker (directly in mnesia) 
> and now things started working again. Is there a better way to re-create 
> the binding to the default exchange without having to re-create the queue?

You should be able to issue an appropriate queue.bind command. As I 
mentioned earlier, such explicit operations on the default exchange 
should imo not be permitted, but rabbit does and it's a grey area of the 
spec. So currently it should work, just don't write any code that 
depends on it.

> I should probably mention that sending the following queue.bind 
> packet didn't seem to help (rabbitmqctl list_bindings still shows the
> binding  missing).
> 
> [:sending,
>  #<AMQP::Protocol::Queue::Bind:0x9b26778
>   @arguments=nil,
>   @debug=1,
>   @exchange=
>    "nanite-rs-instance-fd0416fe31d7b019112c2c0adce9b4e4a261bab1-1094976",
>   @nowait=true,
>   @queue="nanite-rs-instance-fd0416fe31d7b019112c2c0adce9b4e4a261bab1-1094976",
>   @routing_key=nil,
>   @ticket=1>]
> 

The exchange in the above should be blank.


Regards,

Matthias.